Werner Maas, Ph.D.

Creativity in biological research
Maas, Werner
2009 Autumn;52(4):579-584, Perspectives in biology & medicine
During the past century, several biologists have studied the mental processes involved in creativity. In recent years psychologists have approached the subject experimentally. In one such study (Carson, Peterson, and Higgins 2003), creativity has been shown to originate in the subconscious mind and to be transmitted to the conscious mind as a result of a decrease in latent inhibition, an ordinarily strong cognitive barrier between the conscious mind and the subconscious. In my scientific work I have found evidence for creativity in the design of experiments, in which the addition of apparently superfluous controls has led to important discoveries
— id: 105249, year: 2009, vol: 52, page: 579, stat: Journal Article,

The potential for the formation of the arginine biosynthetic enzymes and its masking during evolution
Maas, Werner K
2007 May;29(5):484-488, Bioessays
The present account spans the history of arginine regulation from its discovery in 1955 until the present. In 1957 I demonstrated that not only added arginine but also internally produced arginine represses enzyme formation and that the potential for enzyme synthesis is in excess of what is required for growth. In 1959 I located the regulatory gene argR encoding the arginine repressor. An unusual feature of this research was the finding that in E. coli B, in contrast to E. coli K12, arginine synthesis is permanently repressed, independent of arginine. This was due to a single amino acid difference between the two repressors. Recent studies showed that, in natural populations of E. coli, K12-type regulation is much more frequent than B-type regulation, and that E. coli B evolved from a strain with K12-type regulation. In competition experiments, E. coli K12 was found to be favored in the presence of arginine and E. coli B in its absence, showing that contrary to expectations permanently turned off regulation is favored over negative regulation in some environments.
— id: 72733, year: 2007, vol: 29, page: 484, stat: Journal Article,

My father's life, 1886-1936 : a picture of Jewish life in the Rhenish Palatinate through emancipation, integration, explusion, and annihilation = Das Leben meines Vaters 1888-1936 : ein Bild judischen Lebens in der Rheinpflaz zwischen Emanzipation, Integration, Vertreibung und Vernichtung
Maas, Werner Karl
Speyer : Evangelischer Presseverlag, 2004,
— id: 1696, year: 2004, vol: , page: , stat: ,

Leo Szilard: a personal remembrance
Maas, Werner; Crow, James F
2004 Jun;167(2):555-558, Genetics
— id: 51756, year: 2004, vol: 167, page: 555, stat: Journal Article,

Das Leben meines Vaters 1888-1936 : ein Bild judischen Lebens in der Rheinpflaz zwischen Emanzipation, Integration, Vertreibung und Vernichtung
Maas, Werner Karl
Speyer : Evangelischer Presseverlag Pflaz, 2003,
— id: 1697, year: 2003, vol: , page: , stat: ,

Gene action : a historical account
Maas, Werner Karl
New York : Oxford University Press, 2001,
— id: 1695, year: 2001, vol: , page: , stat: ,

A superrepressor mutant of the arginine repressor with a correctly predicted alteration of ligand binding specificity
Niersbach, H; Lin, R; Van Duyne, G D; Maas, W K
1998 Jun 19;279(4):753-760, Journal of molecular biology
Arginine biosynthesis in Escherichia coli is negatively regulated by the hexameric repressor protein ArgR and the corepressor L-arginine. L-Arginine binds to ArgR in the C-terminal domain of the repressor. Binding to operator DNA occurs in the N-terminal domain. The molecular structures of both domains have recently been elucidated. The known stereochemistry of the arginine binding pocket was used for the rational design of a mutant ArgR with altered ligand specificity. Our prediction was that a replacement of Asp128 by asparagine would preferentially lead to the binding of L-citrulline, rather than L-arginine. The D128N mutant was constructed and was shown to fulfill our expectation by several experimental approaches. By isothermal titration calorimetry it was found to bind L-citrulline much more strongly than L-arginine, in contrast to wild-type ArgR. Exchange between the mutant trimers of the hexamer was inhibited by L-citrulline, as it is by L-arginine in the wild-type. The mutant protein was precipitated by L-citrulline but not by L-arginine, whereas the reverse is true for the wild-type protein. Demonstration of a corepressor action was, however, precluded by the superrepressor effect of the D128N mutation by itself. The mutant protein, in the absence of L-citrulline or L-arginine is as strong a repressor as the wild-type protein in the presence of L-arginine. We discuss two possible mechanisms, in terms of the known domain structures that could explain our observations
— id: 77933, year: 1998, vol: 279, page: 753, stat: Journal Article,

Temperature regulation of heat-labile enterotoxin (LT) synthesis in Escherichia coli is mediated by an interaction of H-NS protein with the LT A-subunit DNA
Trachman JD; Maas WK
1998 Jul;180(14):3715-3718, Journal of bacteriology
Protein and mRNA levels of heat-labile enterotoxin (LT) of Escherichia coli are highest at 37 degrees C, and they decrease gradually as temperature is decreased. This temperature effect is eliminated in an Hns- mutant. Deletion of portions of DNA coding for the LT A subunit also results in an increase in LT expression at low temperatures, suggesting that the H-NS protein causes inhibition of transcription at low temperatures by interacting with the LT A-subunit DNA. The region that interacts with H-NS is referred to as the downstream regulatory element (DRE). Plasmids in an hns strain from which the DRE has been deleted still produce elevated levels of LT at 18 degrees C, suggesting that intact DRE is not required for transcription from the LT promoter
— id: 50748, year: 1998, vol: 180, page: 3715, stat: Journal Article,

Interactions of the RepA1 protein with its replicon targets: two opposing roles in control of plasmid replication
Maas R; Wang C; Maas WK
1997 Jun;179(12):3823-3827, Journal of bacteriology
By studying the interaction of derivatives of RepFIC miniplasmids, we were able to demonstrate that under certain conditions the RepA1 initiator protein inhibits plasmid replication. An analysis of cloned derivatives whose replication is inhibited by the RepA1 protein revealed the existence of two areas of the RepFIC genome that interact with RepA1 in the inhibition reaction. One of these areas, which occurs in the origin region, was explored by in vivo methylation protection footprinting studies. The protected area was 200 bp long and showed a definite periodicity of protected and hypersensitive sites, suggesting that RepA1 promotes a topological change in the RepFIC genome. The significance of our results is discussed in the context of plasmid replication control
— id: 7206, year: 1997, vol: 179, page: 3823, stat: Journal Article,

Multicopy single-stranded DNA of Escherichia coli enhances mutation and recombination frequencies by titrating MutS protein
Maas, W K; Wang, C; Lima, T; Hach, A; Lim, D
1996 Feb;19(3):505-509, Molecular microbiology
Multicopy single-stranded DNA (msDNA) molecules consist of single-stranded DNA covalently linked to RNA. In Escherichia coli, such molecules are encoded by genetic elements called retrons. The DNA moieties of msDNAs have characteristic stem-loop structures, and most of these structures contain mismatched base pairs. Previously, we showed that retrons encoding msDNAs with mismatched base pairs are mutagenic when present in multicopy plasmids. In this study we show that such msDNAs, in a similar manner to genetic defects in mismatch repair, increase the frequency of interspecies recombination in matings between Salmonella typhimurium and E. coli. To demonstrate interference with mismatch repair by msDNA, we show that the addition of a plasmid containing the gene for MutS protein suppresses the mutagenic and recombinogenic effects of msDNAs. We also show that in mutS mutants, msDNA does not increase the frequency of either mutations or interspecies recombination. We conclude from these findings that the mutagenic and recombinogenic effects of msDNAs are due to titrating out MutS protein
— id: 77935, year: 1996, vol: 19, page: 505, stat: Journal Article,

High incidence of retrons in EPEC strains
Maas, WK; Lima, TMO
1996 MAR ;27(3):77-81, Revista de microbiologia
— id: 53014, year: 1996, vol: 27, page: 77, stat: Journal Article,

Structure of the oligomerization and L-arginine binding domain of the arginine repressor of Escherichia coli
Van Duyne, G D; Ghosh, G; Maas, W K; Sigler, P B
1996 Feb 23;256(2):377-391, Journal of molecular biology
The structure of the oligomerization and L-arginine binding domain of the Escherichia coli arginine repressor (ArgR) has been determined using X-ray diffraction methods at 2.2 A resolution with bound arginine and at 2.8 A in the unliganded form. The oligomeric core is a 3-fold rotationally symmetric hexamer formed from six identical subunits corresponding to the 77 C-terminal residues (80 to 156) of ArgR. Each subunit has an alpha/beta fold containing a four-stranded antiparallel beta-sheet and two antiparallel alpha-helices. The hexamer is formed from two trimers, each with tightly packed hydrophobic cores. In the absence of arginine, the trimers stack back-to-back through a dyad-symmetric, sparsely packed hydrophobic interface. Six molecules of arginine bind at the trimer-trimer interface, each making ten hydrogen bonds to the protein including a direct ion pair that crosslinks the two protein trimers. Solution experiments with wild-type ArgR and oligomerization domain indicate that the hexameric form is greatly stabilized upon arginine binding. The crystal structures and solution experiments together suggest possible mechanisms of how arginine activates ArgR to bind to its DNA targets and provides a stereochemical basis for interpreting the results of mutagenesis and biochemical experiments with ArgR
— id: 77934, year: 1996, vol: 256, page: 377, stat: Journal Article,

The DNA-binding domain of the hexameric arginine repressor
Grandori, R; Lavoie, T A; Pflumm, M; Tian, G; Niersbach, H; Maas, W K; Fairman, R; Carey, J
1995 Nov 24;254(2):150-162, Journal of molecular biology
The arginine repressor of Escherichia coli is a classical feedback regulator, signalling the availability of L-arginine inside the cell. It differs from most other bacterial repressors in functioning as a hexamer, but structural details have been lacking and its shares no clear sequence homologies with other transcriptional regulators. Analysis of the amino acid residue sequence and proteolytic cleavage pattern of the repressor was used to identify a region predicted to house the DNA-binding function. When this protein fragment is overexpressed from a clone of the corresponding gene fragment, it represses ornithine transcarbamylase levels in vivo, and binds to the operator DNA in vitro, both in an arginine-independent manner. Sedimentation equilibrium and gel filtration indicate that the purified protein fragment is a monomer in solution. The results thus define the domain organization of the repressor at low resolution, suggesting that the N and C-terminal portions of the polypeptide chain are separated by a structural and functional border that decouples hexamerization and arginine binding from DNA binding
— id: 77936, year: 1995, vol: 254, page: 150, stat: Journal Article,

D-serine deaminase is a stringent selective marker in genetic crosses
Maas WK; Maas R; McFall E
1995 Jan;177(2):459-461, Journal of bacteriology
The presence of the locus for D-serine deaminase (dsd) renders bacteria resistant to growth inhibition by D-serine and enables them to grow with D-serine as the sole nitrogen source. The two properties permit stringent selection in genetic crosses and make the D-serine deaminase gene an excellent marker, especially in the construction of strains for which the use of antibiotic resistance genes as selective markers is not allowed
— id: 12834, year: 1995, vol: 177, page: 459, stat: Journal Article,

RETRONS - RETROELEMENTS OF NO KNOWN FUNCTION - RESPONSE
MAAS, WK
1995 JUN ;3(6):211-212, Trends in microbiology
— id: 87271, year: 1995, vol: 3, page: 211, stat: Journal Article,

The arginine repressor of Escherichia coli
Maas, W K
1994 Dec;58(4):631-640, Microbiological reviews
This review tells the story of the arginine repressor of Escherichia coli from the time of its discovery in the 1950s until the present. It describes how the research progressed through physiological, genetic, and biochemical phases and how the nature of the repressor and its interaction with its target sites were unraveled. The studies of the repression of arginine biosynthesis revealed unique features at every level of the investigations. In the early phase of the work they showed that the genes controlled by the arginine repressor were scattered over the linkage map and were not united, as in other cases, in a single operon. This led to the concept of the regulon as a physiological unit of regulation. It was also shown that different alleles of the arginine repressor could result in either inhibition of enzyme formation, as in E. coli K-12, or in stimulation of enzyme formation, as in E. coli B. Later it was shown that the arginine repressor is a hexamer, whereas other repressors of biosynthetic pathways are dimers. As a consequence the arginine repressor binds to two palindromic sites rather than to one. It was found that the arginine repressor not only acts in the repression of enzyme synthesis but also is required for the resolution of plasmid multimers to monomers, a completely unrelated function. Finally, the arginine repressor does not possess characteristic structural features seen in other prokaryotic repressors, such as a helix-turn-helix motif or an antiparallel beta-sheet motif. The unique features have sustained continuous interest in the arginine repressor and have made it a challenging subject of investigation
— id: 77937, year: 1994, vol: 58, page: 631, stat: Journal Article,

Multicopy single-stranded DNAs with mismatched base pairs are mutagenic in Escherichia coli
Maas, W K; Wang, C; Lima, T; Zubay, G; Lim, D
1994 Nov;14(3):437-441, Molecular microbiology
Retrons are genetic elements that encode multicopy single-stranded DNAs called msDNAs. They are clonally distributed in Escherichia coli and retrons in different clones produce DNAs with different nucleotide sequences. msDNAs consist of an RNA molecule covalently linked to a single-stranded DNA molecule. The latter contains an inverted repeat, resulting in a stem-loop structure. In two retrons, Ec83 and Ec78, the DNA is cleaved off from the RNA. All known retrons except Ec78, have one or more mismatched base pairs in the stem-loop structure. We found that two retrons, Ec86 and Ec83, when present in high copy numbers are mutagenic. The ratios of mutation frequencies observed in Lac- indicator strains were similar to the ratios observed for a mutant defective in mismatch repair. It is known that some proteins required for mismatch repair bind to mismatched base pairs prior to carrying out repair. The similarity in the mutation frequency ratios suggested that the mutagenesis caused by msDNAs of retrons Ec86 and Ec83 might be due to sequestration of a mismatch repair protein by msDNA. Strong support for this interpretation was obtained from the finding that the msDNA produced by retron Ec78 is not mutagenic
— id: 77938, year: 1994, vol: 14, page: 437, stat: Journal Article,

Explanation for different types of regulation of arginine biosynthesis in Escherichia coli B and Escherichia coli K12 caused by a difference between their arginine repressors
Tian G; Lim D; Oppenheim JD; Maas WK
1994 Jan 7;235(1):221-230, Journal of molecular biology
In Escherichia coli K12, formation of the enzymes of arginine biosynthesis are controlled by arginine, with complete repression during growth with added arginine, severe repression (about 95%) during growth without added arginine and complete derepression during arginine-limited growth. In E. coli B, the degree of repression is not correlated with arginine concentrations. Under all conditions of growth enzyme formation is repressed, with repression being somewhat less in a medium with arginine than in a medium without arginine. These differences in repressibility between the two strains have been shown previously to be due to the presence of different alleles of argR, the gene for the arginine repressor. Here we have compared the binding of the two repressors to the operator sites of argF (ARG boxes). In DNase I footprinting and gel retardation experiments with argF ARG boxes we have shown that the arginine repressor of E. coli K12 bound to arginine (ArgRK-arg) has a greater affinity than the arginine repressor of E. coli B bound to arginine (ArgRB-arg), whereas free ArgRB (ArgRBf) has a much stronger affinity than free ArgRK (ArgRKf). The stronger binding of ArgRBf can explain the repression seen in E. coli B during arginine-limited growth and indicates that ArgRBf, but not ArgRKf, is able to repress enzyme synthesis under physiological conditions. The weaker repression of E. coli B than of E. coli K12 seen in the presence of arginine can be explained by the lower affinity of ArgRB-arg for operator sites as compared to ArgRK-arg. Another contributing cause for the weaker repression is the reduction of ArgRBf concentration due to autoregulation of the gene for the repressor. Thus the combined effects of repression by ArgRBf, but not ArgRKf, with the weaker repression by ArgRB-arg as compared to ArgRK-arg, convert the arginine dependent regulation in E. coli K12 to arginine independent regulation in E. coli B
— id: 6537, year: 1994, vol: 235, page: 221, stat: Journal Article,

Mutational analysis of the arginine repressor of Escherichia coli
Tian, G; Maas, W K
1994 Aug;13(4):599-608, Molecular microbiology
Arginine biosynthesis in Escherichia coli is negatively regulated by a hexameric repressor protein, encoded by the gene argR and the corepressor arginine. By hydroxylamine mutagenesis two types of argR mutants were isolated and mapped. The first type is transdominant. In heterodiploids, these mutant polypeptides reduce the activity of the wild-type repressor, presumably by forming heteropolymers. Four mutant repressor proteins were purified. Two of these map in the N-terminal half of the protein. Gel retardation experiments showed that they bind poorly to DNA, but they could be precipitated by L-arginine at the same concentration as the wild-type repressor. The other two mutant repressors map in the C-terminal half of the protein. They are poorly precipitated by L-arginine and they bind poorly to DNA. In addition, one of these mutants appears to exist as a dimer. The second type of argR mutant repressor consists of super-repressors. Such mutants behave as arginine auxotrophs as a result of hyper-repression of arginine biosynthetic enzymes. They map at many locations throughout the argR gene. Three arginine super-repressor proteins were purified. In comparison with the wild-type repressor, two of them were shown to have a higher DNA-binding affinity in the absence of bound arginine, while the third was shown to have a higher DNA-binding affinity when bound to arginine
— id: 77939, year: 1994, vol: 13, page: 599, stat: Journal Article,

Binding of the arginine repressor of Escherichia coli K12 to its operator sites
Tian, G; Lim, D; Carey, J; Maas, W K
1992 Jul 20;226(2):387-397, Journal of molecular biology
In the arginine regulon of Escherichia coli K12 each of the eight operator sites consists of two 18-base-pair-long palindromic sequences called ARG boxes. In the operator sites for the structural genes of the regulon the two ARG boxes are separated by three base-pairs, in the regulatory gene argR they are separated by two base-pairs. The hexameric arginine repressor, the product of argR, binds to the two ARG boxes in an operator in the presence of L-arginine. From the results of various kinds of in vitro footprinting experiments with the ARG boxes of argF and argR (DNase I protection, hydroxyl radical, ethylation and methylation interference, methylation protection) it can be concluded that: (1) the repressor binds simultaneously to two adjacent ARG boxes; (2) that it binds on one face of the double helix; and (3) that it forms contacts with the major and minor grooves of each ARG box, but not with the central three base-pairs. The repressor can bind also to a single ARG box, but its affinity is about 100-fold lower than for two ARG boxes. From gel retardation experiments with 3H-labeled repressor and 32P-labeled argF operator DNA, it is concluded that the retarded DNA-protein complex contains no more than one repressor molecule per operator site and that most likely one hexamer binds to two ARG boxes. The bound repressor was shown to induce bending of argF operator DNA. The bending angle calculated from the results of gel retardation experiments is about 70 degrees and the bending center was located within the region encompassing the ARG boxes. The main features that distinguish the arginine repressor from other repressors studied in E. coli are its hexameric nature and the simultaneous binding of one hexameric molecule to two palindromic ARG boxes that are close to each other
— id: 77940, year: 1992, vol: 226, page: 387, stat: Journal Article,

Isolation and properties of the RepA1 protein of the IncFII replicon, RepFIC [published erratum appears in Mol Microbiol 1991 Dec;5(12):3089]
Maas R; Oppenheim J; Saadi S; Fuchs T; Maas WK
1991 Apr;5(4):927-932, Molecular microbiology
The initiator protein RepA1 of the IncFII replicon RepFIC derived from the enterotoxin plasmid EntP307 has been cloned under the control of the lambda PL promoter. This has enabled us to overproduce this protein and study its properties. Here we show that RepA1 is a soluble basic protein with an experimentally determined molecular weight of 40,000. Deletion analysis indicates that the overproduced protein originates from the open reading frame which we previously designated as coding for RepA1. We have also shown that the replication function of the replicon RepFIC depends on the intact RepA1 coding frame
— id: 14084, year: 1991, vol: 5, page: 927, stat: Journal Article,

The regulation of arginine biosynthesis: its contribution to understanding the control of gene expression
Maas, W K
1991 Jul;128(3):489-494, Genetics
— id: 77941, year: 1991, vol: 128, page: 489, stat: Journal Article,

Expression of the cloned gene for enterotoxin STb of Escherichia coli
Lawrence, R M; Huang, P T; Glick, J; Oppenheim, J D; Maas, W K
1990 Apr;58(4):970-977, Infection & immunity
This study involved the construction of hybrid plasmids to produce heat-stable enterotoxin type II of Escherichia coli (STb). The translation of the open reading frame for the STb gene estA was demonstrated in several ways. Studies using in vivo labeling with [35S]cysteine demonstrated a radiolabeled protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the expected molecular weight of 5,000 for toxin STb. Insertion of translational or transcriptional termination signals into the BglII site of the estA gene blocked the expression of estA. The estA gene was cloned into high-expression vector pKC30 downstream from the strong pL promoter. Northern (RNA) blotting assays revealed a 10- to 20-fold increase in mRNA produced by strain C600F(pKC30STb) over other STb-producing strains, compared with little or no increase in enterotoxin activity demonstrated by bioassay. The estA gene, with its own promoter and Shine-Delgarno region and a portion of the sequence for the signal peptide deleted, was also inserted under the control of the tac promoter. Even after induction of the tac promoter by addition of isopropyl-beta-D-thiogalactopyranoside, no biologic enterotoxin activity could be identified. Neutralizing antibodies to STb were produced in rabbits by using either a purified OmpF-STb-beta-galactosidase fusion protein or a 19-amino-acid synthetic STb peptide coupled to keyhole limpet hemocyanin
— id: 67823, year: 1990, vol: 58, page: 970, stat: Journal Article,

Distribution of msDNAs among serotypes of enteropathogenic Escherichia coli strains
Lim, D; Gomes, T A; Maas, W K
1990 Oct;4(10):1711-1714, Molecular microbiology
A genetic element, called a retron, is present in certain Escherichia coli strains. It consists of genes for the production of a covalently linked DNA-RNA compound and a reverse transcriptase. The presence of a retron can be detected by testing for a satellite DNA band by polyacrylamide gel electrophoresis. This DNA band consists of the DNA portion of the DNA-RNA compound and is called msDNA (multicopy single-stranded DNA). In a survey of intestinal E. coli isolates we detected msDNAs in classical enteropathogenic (EPEC) strains and in strains with aggregative adherence to tissue-culture cells (AA), but not in enteroinvasive (EIEC) and enterotoxigenic (ETEC) strains. Among 76 EPEC strains belonging to 14 different serotypes, msDNA was found to be present in 7 serotypes. In total, five different types of msDNA were found, although within each serotype, the msDNAs were the same. These results suggest that different retrons are clonally inherited
— id: 77943, year: 1990, vol: 4, page: 1711, stat: Journal Article,

Mapping of the msDNA operon in the chromosome of Escherichia coli B
Lim, D; Maas, W K
1990 Dec;4(12):2201-2204, Molecular microbiology
An msDNA operon, consisting of genes for msDNA and a reverse transcriptase, is present in Escherichia coliB and absent from E. coliK12. We have found that the msDNA operon is located on a DNA fragment, longer than 15kb, that is absent from E. coliK12. Using conjugation, P1 transduction, and nucleic acid hybridization between E. coliB and E. coliK12 strains, we have located the position of the msDNA operon on the E. coliB chromosome at a site that corresponds to minute 19 on the genetic map and to position 900 on the physical map of the E. coliK12 chromosome
— id: 77942, year: 1990, vol: 4, page: 2201, stat: Journal Article,

Reverse transcriptase in bacteria
Lim D; Maas WK
1989 Aug;3(8):1141-1144, Molecular microbiology
Reverse transcriptase, discovered in 1970 in retroviruses, has until recently been found only in eukaryotic organisms. Recently it was shown to occur in two groups of bacteria: myxobacteria and Escherichia coli. The gene for reverse transcriptase is part of a chromosomal genetic element that codes for the production of a branched DNA-RNA compound. In this compound a single-stranded DNA is connected to RNA at a specific G residue by a 2'-5' phosphodiester linkage. The precursor for the DNA-RNA compound is a folded messenger RNA, in which the specific G residue is the initiation point for reverse transcription. In the final DNA-RNA compound, the portion of the RNA transcribed by reverse transcriptase is eliminated by RNase H. The DNA-RNA compound is present in several hundred copies per cell. Its biological function is unknown at present
— id: 63362, year: 1989, vol: 3, page: 1141, stat: Journal Article,

Reverse transcriptase-dependent synthesis of a covalently linked, branched DNA-RNA compound in E. coli B
Lim D; Maas WK
1989 Mar 10;56(5):891-904, Cell
We have found a branched DNA-RNA compound in E. coli B, that is similar in its secondary structure, but not its nucleotide sequence, to the previously described branched DNA-RNA compounds in myxobacteria. This compound is not produced in E. coli K12. We have cloned a 3.5 kb chromosomal segment of E. coli B, which, when transferred into E. coli K12, leads to the production of the DNA-RNA compound. We describe the isolation of the DNA-RNA compound, the determination of its nucleotide sequence, and the nucleotide sequence of the genes required for its formation. The sequence contains the coding regions for the DNA component, the RNA component, and an open reading frame encoding a reverse transcriptase. This reverse transcriptase is shown to be required for the formation of the DNA-RNA compound in vivo and in vitro
— id: 63325, year: 1989, vol: 56, page: 891, stat: Journal Article,

Properties and incompatibility behavior of miniplasmids derived from the bireplicon plasmid pCG86
Maas R; Saadi S; Maas WK
1989 Aug;218(2):190-198, Molecular & general genetics
Many plasmids belonging to the F incompatibility groups contain more than one basic replicon. The chimeric plasmid pCG86 is an example of such a multireplicon plasmid. The two basic replicons of pCG86, RepFIIA/FIC and RepFIB have been cloned and re-ligated, the copy numbers of the clones have been determined, and the incompatibility behavior of plasmids containing the ligated replicons and the individual replicons has been studied. The bireplicon plasmids are not expected to be incompatible as recipients with monoreplicon RepFIB or RepFIIA/RepFIC plasmids, since when one replicon is challenged by an incoming replicon, the other should be able to handle the plasmid's replication. In our studies, we found that challenge with either monoreplicon plasmid resulted in incompatibility. This incompatibility was increased in bireplicon plasmids in which RepFIB was duplicated. We conclude that in the bireplicon plasmids, challenging the replication control of one replicon by an incompatible plasmid can interfere with the replication originating from the second replicon
— id: 10533, year: 1989, vol: 218, page: 190, stat: Journal Article,

Identification and classification of bacterial plasmids
Couturier, M; Bex, F; Bergquist, P L; Maas, W K
1988 Sep;52(3):375-395, Microbiological reviews
— id: 77944, year: 1988, vol: 52, page: 375, stat: Journal Article,

A basic replicon of virulence-associated plasmids of Shigella spp. and enteroinvasive Escherichia coli is homologous with a basic replicon in plasmids of IncF groups
Silva, R M; Saadi, S; Maas, W K
1988 Apr;56(4):836-842, Infection & immunity
Shigella species and enteroinvasive Escherichia coli strains carry a large (120- to 140-megadalton) plasmid called pINV, which contains genes essential for the invasiveness of these pathogens. Hybridization with specific probes derived from the RepFIC and RepFIB replicons of the IncF1 Ent plasmid P307 showed that pINVs present in 35 clinical isolates are homologous with RepFIC but not RepFIB, regardless of the serogroup of the Shigella or E. coli strain. RepFIC of P307, in turn, is very similar to RepFIIA replicons of IncFII R plasmids. These and other related replicons constitute the RepFIIA family. With one pINV, pWR110, a plasmid of Shigella flexneri 5, we demonstrated the existence of a functional replicon, RepINV, with a restriction map similar to that of RepFIIA of plasmid R1. We isolated the putative inc RNA coding region of RepINV, which is a major determinant of incompatibility. The nucleotide sequence of the RepINV-inc RNA-coding region was determined and compared with the corresponding sequences of RepFIC and RepFIIA. The differences were small, but apparently were sufficient to affect the target specificity of the inc RNAs, thus rendering the replicons compatible with each other. We conclude that pINVs present in Shigella spp. and enteroinvasive E. coli constitute a homogeneous group, containing one basic replicon that belongs to the RepFIIA family of replicons
— id: 77945, year: 1988, vol: 56, page: 836, stat: Journal Article,

Recombinant DNA technology and enterotoxigenic Escherichia coli vaccines
Gyles, C L; Maas, W K
1987 ;3:139-158, Progress in veterinary microbiology & immunology
— id: 77947, year: 1987, vol: 3, page: 139, stat: Journal Article,

Nucleotide sequence of the argR gene of Escherichia coli K-12 and isolation of its product, the arginine repressor
Lim DB; Oppenheim JD; Eckhardt T; Maas WK
1987 Oct;84(19):6697-6701, Proceedings of the National Academy of Sciences of the United States of America
In Escherichia coli, the arginine repressor, the product of the argR gene, in conjunction with L-arginine controls the synthesis of the enzymes of arginine biosynthesis. We describe the nucleotide sequence of the argR gene, including its control region, and show that formation of the repressor is autoregulated. The argR control region contains two promoters, one of which overlaps the operator site and, as with other arg genes, consists of two adjacent palindromic sequences ('ARG boxes'). The arginine repressor protein and an arginine repressor-beta-galactosidase fusion protein were purified, and the amino acid sequence of the N-terminal end of the repressor protein portion of the fusion protein was determined. Antibodies prepared against the fusion protein react with the repressor. The repressor is precipitable by L-arginine, which facilitates its purification. The native repressor is a hexamer with a molecular weight of 98,000; its monomeric subunit has a molecular weight of 16,500. To verify its properties postulated from genetic studies, we show that in the presence of L-arginine, repressor inhibits transcription of argF and binds to the ARG boxes of argF and argR
— id: 11360, year: 1987, vol: 84, page: 6697, stat: Journal Article,

Nucleotide sequence analysis of RepFIC, a basic replicon present in IncFI plasmids P307 and F, and its relation to the RepA replicon of IncFII plasmids
Saadi, S; Maas, W K; Hill, D F; Bergquist, P L
1987 May;169(5):1836-1846, Journal of bacteriology
RepFIC is a basic replicon of IncFI plasmid P307 which is located within a 3.09-kilobase SmaI fragment. The nucleotide sequence of this region has been determined and shown to be homologous with the RepFIIA replicon of IncFII plasmids. The two replicons share three homologous regions, HRI, HRII, and HRIII, which are flanked by two nonhomologous regions, NHRI and NHRII. A comparison of coding regions reveals that the two replicons have several features in common. RepFIC, like RepFIIA, codes for a repA2 protein with its amino-terminal codons in HRI and its carboxy-terminal codons in NHRI. Although the codons for the repA1 proteins are located in NHRII, the DNA region containing a putative promoter, ribosomal binding site, and initiation codons is located in HRII. This region also codes for an inc RNA. There are nine base-pair differences between the inc RNA of RepFIIA and that of RepFIC, and as a result, RepFIC and RepFIIA replicons are compatible. An EcoRI fragment from the F plasmid which shows homology with RepFIC of P307 has also been sequenced. This fragment contains only a portion of RepFIC, including the genes for the putative repA2 protein and inc RNA. The region coding for a putative repA1 protein is interrupted by the transposon Tn1000 and shows no homology with the repA1 region of RepFIIA and RepFIC of P307. Our comparative and structural analyses suggest that RepFIC and RepFIIA, although different, have a similar replication mechanism and thus can be assigned to the same replicon family, which we designate the RepFIIA family
— id: 77946, year: 1987, vol: 169, page: 1836, stat: Journal Article,

Distribution of basic replicons having homology with RepFIA, RepFIB, and RepFIC among IncF group plasmids
Bergquist, P L; Saadi, S; Maas, W K
1986 Jan;15(1):19-34, Plasmid
Plasmids encoding F-like pili have been divided into groups on the basis of their incompatibility behavior. Three basic replicons have been recognized previously in the IncFI plasmid group and we have now examined their distribution in representative plasmids from 22 of the currently recognized incompatibility groups. The occurrence of these basic replicons was found to be rare outside of the IncF group, and significant hybridization was shown only for RepFIA to IncH1 and I group plasmids. Homology to the RepFIC basic replicon was found in all but one of the IncF group plasmids examined but RepFIA and RepFIB have a more restricted distribution. It appears likely that some plasmids carry vestiges of replicons which still express incompatibility but are incapable of replication. We suggest that evolutionary divergence among the plasmids of the IncF group has resulted from various genetic rearrangements among these basic replicons
— id: 77948, year: 1986, vol: 15, page: 19, stat: Journal Article,

Increased survival from peritonitis after blockade of transdiaphragmatic absorption of bacteria
Dumont AE; Maas WK; Iliescu H; Shin RD
1986 Mar;162(3):248-252, Surgery, gynecology & obstetrics
Based upon the knowledge that bacteria in the peritoneal cavity gain access to circulating blood by way of transdiaphragmatic absorption into lymph, a study was carried out to determine whether this absorption protects or endangers the host. Blockade of absorption produced by intraperitoneal (IP) injection of platelet rich plasma (PRP) or by scarification of the peritoneal surface of the diaphragm increased survival time in rats with double colonic perforation from 20 per cent in control rats to 86 and 93 per cent, respectively. Each of these maneuvers significantly increased the number of negative blood culture findings
— id: 65242, year: 1986, vol: 162, page: 248, stat: Journal Article,

Construction of a conjugative plasmid with potential use in vaccines against heat-labile enterotoxin
Chen, T M; Mazaitis, A J; Maas, W K
1985 Jan;47(1):5-10, Infection & immunity
A conjugative plasmid with potential usefulness for vaccine strains was constructed. In the first step, a 5.9-kilobase DNA segment containing the two loci for the A and B subunits of heat-labile enterotoxin with a mutation in the gene for the A subunit was joined to the cloning vehicle pGA22, generating the nonconjugative plasmid pPMC4 with genes for resistance to tetracycline and chloramphenicol. In the second step, a segment of pPMC4 containing the genes for the A and B subunits, the gene for chloramphenicol resistance, and the replication genes of pGA22 was ligated to the genes for conjugal transfer of the F plasmid, generating the 54.9-kb plasmid pPMC5. Eleven porcine Escherichia coli isolates were tested as recipients for pPMC4 and pPMC5. For pPMC4, transformation and mobilization with a conjugative R plasmid were used to effect plasmid transfer. Only 1 of the 11 strains acted as a recipient in transformation. Mobilization with the R plasmid occurred with two strains, but the plasmids were altered during transfer. In contrast, pPMC5 was transferred with high frequency and unaltered to 9 of the 11 E. coli strains. Transconjugants from these nine matings produced high titers of the B subunit and no active heat-labile enterotoxin. Plasmid pPMC5 was stable in three porcine E. coli strains tested; plasmid pPMC4 was somewhat less stable in these strains. The method we describe for the construction of conjugative chimeric plasmids offers an opportunity for introducing genes with potential for immunization into bacterial strains that are suitable for colonizing the appropriate host sites
— id: 77950, year: 1985, vol: 47, page: 5, stat: Journal Article,

Detection of genes for heat-stable enterotoxin I in Escherichia coli strains isolated in Brazil
Maas, R; Silva, R M; Gomes, T A; Trabulsi, L R; Maas, W K
1985 Jul;49(1):46-51, Infection & immunity
Heat-stable enterotoxin I (STI) can be assayed in intestinal loops of pigs and rabbits and in the gut of infant mice. To produce a simpler and more discriminating assay procedure, we used three gene probes corresponding to three forms of STI called STIa, STIb, and STIc. We tested 159 Brazilian isolates, of which 40 were positive in the infant mouse assay. The STIb and STIc probes are similar (93% DNA homology) and are both different from the STIa probe (70% DNA homology). Of 33 strains that were still active for STI 3 years after their isolation, 25 reacted with both the STIb and STIc probes, 4 reacted with the STIc probe only, and 7 reacted strongly with the STIa probe and weakly or not at all with the other probes. Two strains reacted with all three probes. Further analysis showed that each of these two strains contains a small plasmid that reacts with the STIa probe and a large plasmid that reacts with the STIc probe in one strain and weakly with both the STIa and STIc probes in the other strain. It was also shown that the STIa probe reacts with the cloning vehicle pACYC184 used for the cloning of STIc. We conclude that the gene probes used can identify most STI-producing strains and that in cases of positive responses with several probes careful scrutiny is necessary for analysis
— id: 77949, year: 1985, vol: 49, page: 46, stat: Journal Article,

High incidence of transposon Tn3 insertions into a replication control gene of the chimeric R/Ent plasmid pCG86 of Escherichia coli
Picken, R N; Mazaitis, A J; Maas, W K
1984 Oct;160(1):430-433, Journal of bacteriology
Insertion of transposon Tn3 into the chimeric R/Ent plasmid pCG86 occurred preferentially into a replication control gene, generating mutants with increased plasmid copy number. In two mutants, the nucleotide sequence of the region of the gene containing the Tn3 insertion was determined
— id: 77951, year: 1984, vol: 160, page: 430, stat: Journal Article,

Restriction enzyme maps of the chimeric R/Ent plasmid pCG86 and the related ent plasmid P307
Picken, R N; Mazaitis, A J; Maas, W K
1984 Jan;11(1):102-104, Plasmid
Complete restriction enzyme cleavage site maps for three enzymes and incomplete maps for four enzymes have been constructed for the chimeric R/Ent plasmid pCG86 of Escherichia coli and the related Ent plasmid P307
— id: 77954, year: 1984, vol: 11, page: 102, stat: Journal Article,

Characterization of the basic replicons of the chimeric R/Ent plasmid pCG86 and the related Ent plasmid P307
Picken, R N; Mazaitis, A J; Saadi, S; Maas, W K
1984 Jul;12(1):10-18, Plasmid
Restriction-enzyme fragments that can replicate autonomously after circularization were isolated from the chimeric R/Ent plasmid pCG86 and the Ent plasmid P307. Two such regions containing a basic replicon were located in each plasmid. One of the basic replicons of P307, RepFIB, is almost identical with one of the basic replicons of pCG86. The other basic replicon in P307, RepFIC, is partly homologous with the second basic replicon in pCG86, RepFIIA/RepFIC. The latter is a hybrid basic replicon and is in addition partly homologous with RepFIIA, a basic replicon present in IncFII R plasmids. By restriction-enzyme mapping and nucleotide-sequence analysis we have determined a site in the hybrid replicon where it ceases to be homologous with the RepFIIA basic replicon contained in the IncFII miniplasmid pSM1. The 2410-bp region of homology with pSM1 corresponds with a segment containing the origin of replication and all the genes responsible for replication control of pSM1
— id: 77953, year: 1984, vol: 12, page: 10, stat: Journal Article,

RepFIC, a basic replicon of IncFI plasmids that has homology with a basic replicon of IncFII plasmids
Saadi, S; Maas, W K; Bergquist, P L
1984 Jul;12(1):61-64, Plasmid
It was found that a DNA segment containing genes for autonomous replication and its control (basic replicon) present in the IncFI plasmid P307 has homology with RepA, a basic replicon present in IncFII plasmids. The basic replicon in P307 is referred to as RepFIC and the homologous basic replicon in IncFII plasmids is referred to as RepFIIA. In 11 other IncFI plasmids studied a region that has homology with RepFIC and RepFIIA was demonstrated. Thus, of the several basic replicons present in IncFI plasmids, RepFIC is evolutionarily related to a basic replicon of IncFII plasmids
— id: 77952, year: 1984, vol: 12, page: 61, stat: Journal Article,

GENE-FUNCTION - ESCHERICHIA-COLI AND ITS HERITABLE ELEMENTS - GLASS,RE
MAAS, WK
1983 ;58(4):559-559, Quarterly review of biology
— id: 51030, year: 1983, vol: 58, page: 559, stat: Journal Article,

Nucleotide sequence of the gene for heat-stable enterotoxin II of Escherichia coli
Picken, R N; Mazaitis, A J; Maas, W K; Rey, M; Heyneker, H
1983 Oct;42(1):269-275, Infection & immunity
Previously, the gene for heat-stable enterotoxin II (STII) has been mapped by transposon Tn5 insertion mutagenesis in the chimeric R-Ent plasmid pCG86 (Mazaitis, A. J., R. Maas, and W. K. Maas, J. Bacteriol. 145:97-105, 1981). DNA segments containing this gene were cloned from the wild-type and STII-insertion-mutant plasmid. The position of the Tn5 insertion was determined, and a 530-base-pair-long segment of the wild-type plasmid corresponding to the Tn5 insertion site was sequenced. An open reading frame for the STII gene was identified and is characterized by typical promoter and ribosome binding site sequences. The deduced STII structural gene codes for a protein 71 amino acids long, including a typical signal peptide of 23 amino acids and a mature protein of 48 amino acids. The size and overall structure of STII are similar to those of STI, but the amino acid compositions of the two heat-stable enterotoxins are completely different
— id: 77955, year: 1983, vol: 42, page: 269, stat: Journal Article,

MAPPING OF TN3 INSERTIONS INTO AN ENT PLASMID RESULTING IN INCREASED PRODUCTION OF HEAT LABILE ENTERO-TOXIN
PICKEN, R; MAZAITIS, AJ; MAAS, WK
1982 ;8(1):98-98, Plasmid
— id: 50547, year: 1982, vol: 8, page: 98, stat: Journal Article,

Genetic aspects of toxigenesis in bacteria
Maas, W K
1981 ;13(1):205-217, Pharmacology & therapeutics
— id: 77956, year: 1981, vol: 13, page: 205, stat: Journal Article,

Structure of a naturally occurring plasmid with genes for enterotoxin production and drug resistance
Mazaitis, A J; Maas, R; Maas, W K
1981 Jan;145(1):97-105, Journal of bacteriology
A physical map of the 117-kilobase conjugative plasmid pCG86 was constructed using electron microscope heteroduplex analysis. This plasmid carries the genes elt, for heat-labile enterotoxin, and estA, for heat-stable enterotoxin, as well as the genes for resistance to tetracycline, streptomycin, sulfonamides, and mercury. These genes were mapped using deletions and Tn5 insertions as physical markers. Analysis of a heteroduplex between pCG86 and a previously described enterotoxin plasmid (EntP307) showed a 48-kilobase region of complete homology which included the genes elt and estA. An 8.8-kilobase BamHI fragment of EntP307 carrying elt, cloned by others, was also shown to be completely homologous with pCG86. The position of elt on the fragment was verified, and it was shown to carry estA as well. A 44-kilobase region of pCG86 showed partial homology with the region of EntP307 previously shown to contain conjugal transfer genes. The gene for tetracycline resistance is carried on a stem-loop structure with the dimensions of Tn10, and the genes for the other drug resistance markers are carried on a 14.6-kilobase segment that forms an insertion loop in heteroduplexes with EntP307. These studies suggest that pCG86 arose either by recombination between an enterotoxin plasmid of incompatibility group FI, like EntP307, and a multiple resistance factor of incompatibility group FII, or by transposition into EntP307 of two transposons
— id: 77957, year: 1981, vol: 145, page: 97, stat: Journal Article,

Escherichia coli regulatory mutation affecting lysine transport and lysine decarboxylase
Popkin, P S; Maas, W K
1980 Feb;141(2):485-492, Journal of bacteriology
A spontaneous thiosine-resistant mutant of Escherichia coli was shown to have the following characteristics: lowered initial rate of lysine uptake and lowered plateau level of accumulation of exogenous lysine by both the lysine-specific and the general basic amino acid transport systems; altered repressibility of these two lysine transport systems; a derepressed level of lysine decarboxylase; normal growth rate; parental levels of lysyl-transfer ribonucleic acid synthetase and the inducible and constitutive arginine and ornithine decarboxylases. Both the mutant (lysP) and its parent (lysP+) feed a lysine auxotroph when they are plated in proximity on solid medium. However, the feeding response was observable after 1 day less of incubation when the mutant was the feeding strain. Despite the derepressed level of lysine decarboxylase in exponential cultures of the mutant extracts of these cultures had no detectable cadaverine pool. Conjugation experiments established the following gene order: gyrA (formerly nalA) lysP metG his. All thiosine-resistant recombinants assayed showed reduced lysine transport. In many of these recombinants the derepression of lysine decarboxylase was not expressed
— id: 77959, year: 1980, vol: 141, page: 485, stat: Journal Article,

Transfer of a CFA/I-ST plasmid promoted by a conjugative plasmid in a strain of Escherichia coli of serotype O128ac:H12
Reis, M H; Heloiza, M; Affonso, T; Trabulsi, L R; Mazaitis, A J; Maas, R; Maas, W K
1980 Jul;29(1):140-143, Infection & immunity
Escherichia coli strains belonging to serotype O128ac:H12 and producing heat-stable enterotoxin (ST) and colonization factor CFA/I were found in Sao Paulo in children with diarrhea, but not in normal children. Segregants occurred in such strains with a frequency of about 10%, which have lost the ability to produce ST and CFA/I at the same time. From one strain, both properties were transformed jointly in matings to an E. coli K-12 strain. All such ST+ CFA/I+ progeny had received two plasmids of length 97 and 64 kilobases in the matings. Insertion of a transposon, Tn5, carrying a gene for kanamycin resistance, into the two plasmids enabled us to select for kanamycin-resistant progeny in further matings. Analysis of such progeny strains in terms of plasmid content and production of ST and CFA/I revealed that the larger plasmid carries the genes for St and CFA/I and is not self-transmissible, whereas the smaller plasmid does not carry any recognizable phenotypic traits, but is conjugative and promotes cotransfer of the larger plasmid with a frequency of about 30%
— id: 77958, year: 1980, vol: 29, page: 140, stat: Journal Article,

Isolation and characterization of enterotoxin-deficient mutants of Escherichia coli
Silva, M L; Maas, W K; Gyles, C L
1978 Mar;75(3):1384-1388, Proceedings of the National Academy of Sciences of the United States of America
The genes controlling the production of two types of enterotoxin of Escherichia coli, one heat-labile (LT) and the other heat-stable (ST), are found on plasmids. The absence of a direct selection procedure has made it difficult to isolate mutants affecting toxin production. However, the availability of a naturally occurring 'recombinant' plasmid, carrying genes for LT and ST formation and also for resistance to tetracycline, streptomycin, and sulfonamides, made it possible to use comutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine to enrich for such mutants. We have isolated and characterized 58 LT- mutants and 7 ST- mutants. Among the LT- group we found amber mutants, temperature-sensitive mutants (most of which produce unusually heat-labile LT), and 'leaky' mutants with reduced LT activity. The majority of the tested LT- mutants produced immunologically crossreacting material, in most cases in wild-type amounts. Among all 17 of the LT- mutants that could be transferred, the mutation was found to be on the plasmid. In contrast, only one of four transferrable ST- mutants appeared to be a plasmid mutant
— id: 77960, year: 1978, vol: 75, page: 1384, stat: Journal Article,

STUDIES ON BIPOLAR ARGECBH OPERON OF ESCHERICHIA-COLI - CHARACTERIZATION OF RESTRICTION ENDONUCLEASE FRAGMENTS OBTAINED FROM LAMBDADARGECBH TRANSDUCING PHAGES AND A COLE1 ARGECBH PLASMID
CRABEEL, M; CHARLIER, D; GLANSDORFF, N; PALCHAUDHURI, S; MAAS, WK
1977 ;151(2):161-168, Molecular & general genetics
— id: 49882, year: 1977, vol: 151, page: 161, stat: Journal Article,

Naturally occurring plasmid carrying genes for enterotoxin production and drug resistance
Gyles, C L; Palchaudhuri, S; Maas, W K
1977 Oct 14;198(4313):198-199, Science
Escherichia coli strain 86, isolated from a piglet with diarrhea, carries plasmid-linked genes for resistance to tetracycline, streptomycin, and sulfonamides and for production of heat-labile and heat-stable enterotoxin. Results of (i) genetic experiments involving conjugal transfer and phage P1-mediated transduction and (ii) physical experiments involving electron microscopic examination of plasmid DNA and heteroduplex analysis show that a single conjugative plasmid carries the genes for drug resistance and production of enterotoxin
— id: 77962, year: 1977, vol: 198, page: 198, stat: Journal Article,

Physical mapping of a DNA sequence common to plasmids of incompatibility group F I
Palchaudhuri, S; Maas, W K
1977 Mar;74(3):1190-1194, Proceedings of the National Academy of Sciences of the United States of America
We have mapped a region of homology within a 2.2 kilobase segment of plasmids of incompatibility group F I, WHICH IS CONTAINED IN AN EcoRI restriction enzyme fragment bearing genes for autonomous replication; The coordinates of the 2.2 kilobase segment are 46.4F-48.6F on the physical map of the F plasmid. The orgin of vegetative replication has been mapped at 42.5F, at which site F has no sequence homology with other group F I plasmids. Plasmids belonging to other incompatibility groups have no homology with the 46.4-48.6 F segment. Possible mechanisms underlying incompatibility are discussed. We think that incompatibility is due to either a limitation in a common equipartitioning mechanism or a limitation in a common replication control. In either case, the common mechanism is specific for plasmids belonging to a given incompatibility group
— id: 77964, year: 1977, vol: 74, page: 1190, stat: Journal Article,

Physical mapping of genes on the F plasmid of Escherichia coli responsible for inhibition of growth of female-specific bacteriophages
Palchaudhuri, S; Maas, W K
1977 Nov;132(2):740-743, Journal of bacteriology
By correlating the resistance or sensitivity to female-specific phages of strains carrying F plasmids with deletions for part of the region 32.6 to 42.9 F, cloned F fragments, and other plasmids, it was shown that the pif loci are located near and clockwise to a point on F with coordinate 38.3 F
— id: 77961, year: 1977, vol: 132, page: 740, stat: Journal Article,

Characterization of plasmids in a sucrose-fermenting strain of Escherichia coli
Palchaudhuri, S; Rahn, S; Santos, D S; Maas, W K
1977 Jun;130(3):1402-1403, Journal of bacteriology
A multiply drug-resistant strain of Escherichia coli isolated from a patient in Bangladesh was shown to carry four types of plasmids based on size differences. One type carries a gene or genes for sucrose fermentation
— id: 77963, year: 1977, vol: 130, page: 1402, stat: Journal Article,

Amplification of the Escherichia coli K 12 arginine bipolar operon: construction in vitro and cloning of a composite colE1-argECBH plasmid
Crabeel, M; Charlier, D; Glansdorff, N; Maas, W K
1976 ;84(3):593-594, Archives internationales de physiolgoie de biochimie et de biophysique
— id: 77971, year: 1976, vol: 84, page: 593, stat: Journal Article,

Proceedings: Repression in vitro of arginine genes transcription in Escherichia coli
Cunin R; Kelker N; Boyen A; Glansdorff N; Maas WK
1976 Feb;84(1):147-148, Archives internationales de physiolgoie de biochimie et de biophysique
— id: 65768, year: 1976, vol: 84, page: 147, stat: Journal Article,

Involvement of arginine in in vitro repression of transcription of arginine genes C, B and H in Escherichia coli K 12
Cunin, R; Kelker, N; Boyen, A; Yang, H; Zubay, G; Glansdorff, N; Maas, W K
1976 Mar 22;69(2):377-382, Biochemical & biophysical research communications
— id: 77968, year: 1976, vol: 69, page: 377, stat: Journal Article,

In vitro synthesis and repression of argininosuccinase in Escherichia coli K12; partial purification of the arginine repressor
Kelker, N E; Maas, W K; Yang, H L; Zubay, G
1976 Feb 27;144(1):17-20, Molecular & general genetics
Phi80dargECBH DNA has been used to direct cell-free synthesis of argininosuccinase, the argH gene product in Escherichia coli K12. In vitro enzyme synthesis is sensitive to repression by partially purified preparations from an argR+ strain but not by corresponding preparations from an argR- strain. Using DNA-cellulose chromatography, approximately seventyfold purification of repressor has been obtained. The partially purified preparation represses argininosuccinase synthesis but has no effect on beta-galactosidase synthesis
— id: 77969, year: 1976, vol: 144, page: 17, stat: Journal Article,

Isolation and characterization of lambdadargECBH transducing phages and heteroduplex analysis of the argECBH cluster
Mazaitis, A J; Palchaudhuri, S; Glansdorff, N; Maas, W K
1976 Jan 16;143(2):185-196, Molecular & general genetics
Transducing lambda bacteriophages have been isolated which carry the divergently transcribed argECBH operon of E. coli K12 and various portions of the adjacent ppc and bfe chromosomal regions. They were recovered from lysates prepared by the procedure of Schrenk and Weisberg using a Ppc+ Arg+ Bfe+ strain carrying a deletion of the usual attachment site of lambda. Heteroduplex DNA mapping of these lumbdadarg and of the phi 80 darg isolated by B. Konrad indicates that the two kinds of phages carry the arg cluster in opposite orientations, a situation favorable for the isolation of argECBH DNA. A physical map of the ppc argECBH bfe region including 2 unusual attachment sites of lambda has been constructed. The localization of the end points of certain arg deletions provides a useful reference framework for the currently pursued mapping of mutations affecting the control of divergent transcription and for the location of restriction enzyme cleavage sites in the arg region
— id: 77970, year: 1976, vol: 143, page: 185, stat: Journal Article,

Fusion of two F-prime factors in Escherichia coli studied by electron microscope heteroduplex analysis
Palchaudhuri, S; Maas, W K
1976 Aug 2;146(3):215-231, Molecular & general genetics
A fused F prime factor was obtained from a mating of a recA donor carrying an F'- factor containing the genes metBJF, ppc and argECBH (KLF5) with a recA recipient carrying an F' factor containing att80, trp and lac (f155). lysogenization of this fused F-prime factor with gammacI857hphi80 phage followed by thermoinduction produced the transducing phages phi80 dmetBJF and phi80 dppcargECBH. This kind of fusion provides a general procedure for the construction of transducing phages carrying genes from different regions of the E. coli genome. To understand the mechanism of this fusion, the parental F prime factors (F155 and KLF5) were analyzed by the electron microscope heteroduplex technique. F155 has a length of 176 +/- 3 kilobases including two substitutions. The F sequence 0 F-2.8 F has been substituted by 53 kb of chromosomal DNA including the lac operon and the F sequences 8.5 F-16.3 F has been substituted by 27 kb of a chromosome sequence including att80 and the trp operon KLF5 contains 221 +/- 4 kilobases of DNA (molecular weight, 148 megadaltons). It contains complete F and the segment of the E. coli chromosome from polA to rif. The F sequence 2.8 F-8.5 F known to be involved in F specific recombination in recA+ and recA backgrounds occurs twice on KLF5, once at each of the junctions of F DNA with chromosomal DNA. The population of closed circular plasmid molecules extracted from KLF5-containing strains is heterogeneous. It is proposed that this heterogeneity is due to intramolecular recombination events occurring in KLF5 between the duplicated 2.8 F-8.5 F sequences. Such recombination can account for the genetic instability of KLF5 observed in both recA+ and recA hosts. The F sequence 2.8 F-8.5 (also called gammadelta) is one of the characterized integration sequences on F. A model for the fusion of the parental F prime factors is proposed in which recombination between gammadelta sequences brings att80 close to the metBJF genes. This is followed by a deletion of an F' lac factor. The resulting fused F' factor still carries two gammadelta sequences and is therefore expected to be unstable. The closed circular molecules isolated from the fused F' containing strains show two different sizes of molecules. Genetic and physical analyses of these molecules are in agreement with the predicted instability of the fused F' factor and the existance of the gammadelta sequence in the phi80 dmet phages isolated from fused F' and previously analyzed by the electron microscope heteroduplex technique
— id: 77965, year: 1976, vol: 146, page: 215, stat: Journal Article,

Expression of a mutation affecting F incompatibility in the integrated but not the autonomous state of F
Pfister, A; DeVries, J K; Maas, W K
1976 Jul;127(1):348-353, Journal of bacteriology
Previously we have described a mutant Hfr strain in which incompatibility between the integrated F factor and an autonomous F-prime (F') factor was abolished. The mutation (inc) was located in the integrated F factor. F-prime factors isolated from the mutant Hfr strain have the same incompatibility behavior as those isolated from normal Hfr strains. Reintegration of these F' factors into the chromosome restores the Inc- phenotype characteristic of the mutant Hfr. The inc mutation thus affects incompatibility between integrated F and autonomous F(Fi-Fa incompatibility) but not incompatibility between two autonomous F factors (Fa-Fa incompatibility). The implications of this finding for the mechanism of plasmid incompatibility are discussed
— id: 77966, year: 1976, vol: 127, page: 348, stat: Journal Article,

Partial purification and characterization of a heat-labile enterotoxin of Escherichia coli
Schenkein, I; Green, R F; Santos, D S; Maas, W K
1976 Jun;13(6):1710-1720, Infection & immunity
A partially purified enterotoxin was obtained from the growth medium of Escherichia coli strain 711 (P307), a derivative of E. coli K-12, by ultrafiltration, precipitation with ammonium sulfate, molecular sieving, and anion exchange column chromatography. The active moiety, which is heat-labile, behaved like a protein particle of 180,000 to 200,000 daltons during molecular sieving and ultracentrifugation. During polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS-PAGE), it dissociated into two subunits with apparent molecular weights of 68,000 to 70,000 and 14,000 to 15,000. SDS-PAGE after heating in SDS changed the larger subunit to an apparent molecular weight of about 40,000; the smaller subunit did not change. The intact particle induced rounding of the cells in Y-1 mouse adrenal tumor cells used for assay. The detergent-dissociated molecules were not active. Proteolysis of the purified toxin by tolylsulfonyl phenylalanyl chloromethyl ketone-trypsin appeared to enhance its activity. The addition of serum to the assay medium resulted in partial depression of the activity. Activity was also abolished by preincubation of the toxin with either a rabbit antiserum to it or solutions containing GM1 ganglioside. The length of time needed to evoke a response in the assay system by fractions from different stages in the purification of the enterotoxin was a useful parameter in the evaluation of specific activity
— id: 77967, year: 1976, vol: 13, page: 1710, stat: Journal Article,

Ribosomal distribution in a polyamine auxotroph of Escherichia coli
Algranati, I D; Echandi, G; Goldemberg, S H; Cunningham-Rundles, S; Maas, W K
1975 Dec;124(3):1122-1127, Journal of bacteriology
The distribution of ribosomal particles has been studied in a polyamine-deficient mutant of Escherichia coli by sucrose gradient centrifugation analysis. Lysates from starved cells contained less 70S monomers and 30S subunits but more 50S particles than those prepared from bacteria supplemented with putrescine. The addition of the polyamine to putrescine-depleted cells induced a rapid change of the ribosomal profile. A similar effect could be obtained in vitro by equilibrium dialysis against a polyamine-containing solution. The ribosomal pattern obtained from starved bacteria was specific for polyamine deficiency. We conclude that the changes in ribosomal profiles upon restoration of putrescine levels in previously starved cells denote a shift of the equilibrium between 30S-50S couples and ribosomal subunits
— id: 77973, year: 1975, vol: 124, page: 1122, stat: Journal Article,

Isolation, characterization, and mapping of Escherichia coli mutants blocked in the synthesis of ornithine decarboxylase
Cunningham-Rundles, S; Maas, W K
1975 Nov;124(2):791-799, Journal of bacteriology
Several Escherichia coli K-12 mutants blocked in the synthesis of ornithine decarboxylase (OD) were isolated after transduction for serA+ in a strain (MA197) blocked in agmatine ureohydrolase (AUH) with a mutagenized phage lysate of P1. The new double-polyamine mutants were characterized by an unconditional polyamine dependence; either putrescine or spermidine was required for normal growth. The mutational block was varified by the demonstration of a virtual absence of OD activity in cellular extracts. The mutation, designated speC, was mapped by P1 transduction in several strains and was shown to have a cotransduction frequency of 17.2% with serA. Map order was established as serA speB speC metK. A derivative of one of the OD mutants having wild-type levels of AUH and blocked in OD was utilized along with an OD AUH mutant and an OD+ AUH strain to explore the phenomenon of 'pathway selection' using growth rate as a parameter. Polyamine pool studies were carried out simultaneously. The results presented here support the hypothesis of pathway selection, implying a preferential utilization of exogenous arginine rather than endogenously produced arginine in polyamine biosynthesis
— id: 77974, year: 1975, vol: 124, page: 791, stat: Journal Article,

ISOLATION OF ARGININE REPRESSOR FROM ESCHERICHIA-COLI K12
KELKER, N; MAAS, W; ZUBAY, G
1975 ;34(3):621-621, Federation Proceedings (Federation of American Societies for Experimental Biology)
— id: 48833, year: 1975, vol: 34, page: 621, stat: Journal Article,

Genetic and physical characteristics of an enterotoxin plasmid
Santos, D S; Palchaudhuri, S; Maas, W K
1975 Dec;124(3):1240-1247, Journal of bacteriology
We are engaged in the genetic and physical characterization of an enterotoxin (Ent) plasmid, Ent P307, which contains genes for the production of a hear-labile and a heat-stable enterotoxin. We are using an Escherichia coli K-12 strain, 711 (P307), constructed by S. Falkow, which contains no other plasmids besides Ent P307. Our genetic studies have shown that the plasmid is incompatible with the sex factor F, both in the integrated (Hfr) and the autonomous (F-prime) state. Ent P307 can thus be assigned to incompatibility group FI. An R factor, R386, which belongs to the same incompatibility group, was also found to be incompatibile with Ent P307, whereas five other R factors belonging to different incompatibility groups were compatible with Ent P307. In the presence of Ent P307, conjugal transfer and sensitivity to a male-specific phage of a derepressed F-like R factor, R1drd19, were repressed. Ent P307 is, thus, finO+. Presumably, it also causes repression of its own transfer genes since conjugal transfer of Ent P307 could not be demonstrated. Unlike F, it does not restrict the growth of female-specific phage phiII. From physical studies on extracted deoxyribonucleic acid, the molecular weight of Ent P307 was determined to be 54 X 10(6). By electron microscope heteroduplex analysis, the plasmid was found to be homologous with F in four regions, encompassing about half of its length. One long region and two short ones contain genes for conjugal transfer; the other short region carries genes for replication and incompatibility
— id: 77972, year: 1975, vol: 124, page: 1240, stat: Journal Article,

Selection for genetically repressible (ArgR+) strains of Escherichia coli K12 from genetically derepressed (ArgR-) mutants using acetylnorvaline
Kelker, N E; Maas, W K
1974 ;132(2):131-136, Molecular & general genetics
— id: 77975, year: 1974, vol: 132, page: 131, stat: Journal Article,

Mutant of Escherichia coli K-12 defective in the transport of basic amino acids
Celis TF; Rosenfeld HJ; Maas WK
1973 Nov;116(2):619-626, Journal of bacteriology
— id: 21594, year: 1973, vol: 116, page: 619, stat: Journal Article,

Description of an incompatibility mutant of Escherichia coli
DeVries JK; Maas WK
1973 Jul;115(1):213-220, Journal of bacteriology
— id: 63247, year: 1973, vol: 115, page: 213, stat: Journal Article,

STABLE RIBONUCLEIC-ACID SYNTHESIS IN STRINGENT (REL+) AND RELAXED (REL-) POLYAMINE AUXOTROPHS OF ESCHERICHIA-COLI K-12
SRINIVAS.PR; YOUNG, DV; MAAS, W
1973 ;116(2):648-655, Journal of bacteriology
— id: 46742, year: 1973, vol: 116, page: 648, stat: Journal Article,

In vitro repression of n- -acetyl-L-ornithinase synthesis in Escherichia coli
Urm, E; Yang, H; Zubay, G; Kelker, N; Maas, W
1973 ;121(1):1-7, Molecular & general genetics
— id: 129604, year: 1973, vol: 121, page: 1, stat: Journal Article,

Mapping of genes involved in the synthesis of spermidine in Escherichia coli
Maas, W K
1972 ;119(1):1-9, Molecular & general genetics
— id: 77977, year: 1972, vol: 119, page: 1, stat: Journal Article,

Characterization by electron microscopy of fused F-prime factors in Escherichia coli
Palchaudhuri, S R; Mazaitis, A J; Maas, W K; Kleinschmidt, A K
1972 Jul;69(7):1873-1876, Proceedings of the National Academy of Sciences of the United States of America
During previous attempts to find mutants in which incompatibility between two F-prime (F') factors of E. coli is abolished, we found that two F' factors harbored in the same cell occasionally recombined to form a single genetic unit. Thus, a fused F'trp(+)arg(+) factor was obtained from a mating of a strain carrying recA F'trp(+) with a strain carrying recA F'arg(+). In the present paper physical fusion of the two F' factors, inferred from genetic studies, is confirmed by electron microscopy. F DNA was extracted, after detergent lysis, from four fused F' strains: the parental F'trp(+) and F'arg(+) strains and three F(+) strains. This supercoiled DNA was separated on ethidium bromide-cesium chloride gradients and converted to the open circular from before electron microscopy. The contour lengths in mum of the various DNA preparations were: F'trp(+), 59.4; F'arg(+), 33.2; the four F'trp(+)arg(+) factors, 38.5, 39.6, 63.2, and 73.5: the three F factors, 31.1, 31.1, and 31.0. Thus, different fused F' factors formed from the same parental F' factors vary in length, but are shorter than the sum of the parental F' factors
— id: 77976, year: 1972, vol: 69, page: 1873, stat: Journal Article,

Biology of antibiotics
Zahner, Hans; Maas, Werner K
New York : Springer-Verlag, 1972,
— id: 1694, year: 1972, vol: , page: , stat: ,

Studies on the mechanism of repression of arginine biosynthesis in Escherichia coli. IV. Further studies on the role of arginine transfer RNA repression of the enzymes of arginine biosynthesis
Celis, T F; Maas, W K
1971 Nov 28;62(1):179-188, Journal of molecular biology
— id: 21595, year: 1971, vol: 62, page: 179, stat: Journal Article,

Chromosomal integration of F' factors in recombination-deficient Hfr strains of Escherichia coli
DeVries, J K; Maas, W K
1971 Apr;106(1):150-156, Journal of bacteriology
In matings between F' donors and recombination-deficient Hfr recipients, we isolated progeny which transferred both episomal markers and Hfr markers early and with high frequency. A number of these progeny had two integrated sex factors. Investigation of these double Hfr strains showed that the F' nearly always integrated in a homologous region of the chromosome. In any particular mating system integration was specific as to location and direction of chromosome transfer
— id: 77978, year: 1971, vol: 106, page: 150, stat: Journal Article,

Regulatory gene mutations affecting arginine biosynthesis in Escherichia coli
Kadner, R J; Maas, W K
1971 ;111(1):1-14, Molecular & general genetics
— id: 77980, year: 1971, vol: 111, page: 1, stat: Journal Article,

Isolation of transducing particles of phi-80 bacteriophage that carry different regions of the Escherichia coli genome
Press, R; Glansdorff, N; Miner, P; De Vries, J; Kadner, R; Maas, W K
1971 Apr;68(4):795-798, Proceedings of the National Academy of Sciences of the United States of America
It has been possible to mate two strains harboring F-prime (F') factors and to isolate from such matings rare recombinants that behave as though the two episomes had fused. Thus, two genes not previously linked may be brought into close proximity.An F' factor carrying the attachment site for varphi80 was fused with one carrying the met-ppc-arg region of the chromosome. Lysogenization of such a strain, followed by induction, led to the isolation of varphi80arg(+) and varphi80met(+) transducing phages. This technique may be utilized as a general method for joining diverse bacterial genes to the genome of phage varphi80
— id: 77979, year: 1971, vol: 68, page: 795, stat: Journal Article,

Isolation and characterization of a mutant of Escherichia coli blocked in the synthesis of putrescine
Hirshfield, I N; Rosenfeld, H J; Leifer, Z; Maas, W K
1970 Mar;101(3):725-730, Journal of bacteriology
A mutant of Escherichia coli is described which is defective in the conversion of arginine to putrescine. The activity of the enzyme agmatine ureohydrolase is greatly reduced, whereas the activity of the other two enzymes of the pathway, the constitutive arginine decarboxylase and the inducible arginine decarboxylase, are within the normal range. The growth behavior of the mutant reflects the enzymatic block. It grows well in the absence of arginine, but only poorly in the presence of arginine. Under the former conditions, putrescine can be formed from ornithine as well as arginine, whereas under the latter conditions, because of feedback control, it can be formed only from arginine
— id: 77981, year: 1970, vol: 101, page: 725, stat: Journal Article,

Production of a merodiploid strain from a double male strain of E. coli K12
Clark, A J; Maas, W K; Low, B
1969 ;105(1):1-15, Molecular & general genetics
— id: 77984, year: 1969, vol: 105, page: 1, stat: Journal Article,

Map location of arginyl-tRNA synthetase mutations in Escherichia coli K-12
Cooper, P H; Hirshfield, I N; Maas, W K
1969 Aug 15;104(4):383-390, Molecular & general genetics
— id: 77982, year: 1969, vol: 104, page: 383, stat: Journal Article,

Inactivation of a newly transferred gene in recombination-deficient recipients of Escherichia coli
Dubnau, E; Maas, W K
1969 ;103(4):305-312, Molecular & general genetics
— id: 77985, year: 1969, vol: 103, page: 305, stat: Journal Article,

A mutant of Escherichia coli permitting replication of two F factors
Maas, W K; Goldschmidt, A D
1969 Mar;62(3):873-880, Proceedings of the National Academy of Sciences of the United States of America
Control mechanisms of replication of bacterial genetic elements are poorly understood at present. We have studied one such mechanism involving replication of the F factor in Escherichia coli. The F factor can replicate either autonomously in F(+) or F' strains, or as an integral part of the chromosome in Hfr strains. We have shown that presence of either an integrated F factor or a free F factor prevents replication of a second free F factor. Two integrated F factors can replicate in the same cell.The present experiments show that when a F'lac element was transferred by mating into an Hfr strain, it had to become integrated into the chromosome in order to persist. With a recombination-deficient (recA) Hfr strain as recipient, the frequency of F'lac integration was greatly reduced. This permitted us to isolate a mutant Hfr strain in which the F'lac element was able to replicate autonomously. The mutation has most likely occurred in the integrated F factor itself. Availability of this new recA mutant Hfr strain facilitates genetic analysis of the F factor, since in recA(+) Hfr strains frequent integration of a free F factor into the chromosome obscures recognition of complementation and recombination between two free F factors
— id: 77983, year: 1969, vol: 62, page: 873, stat: Journal Article,

Inhibition of replication of an F'lac episome in Hfr cells of Escherichia coli
Dubnau, E; Maas, W K
1968 Feb;95(2):531-539, Journal of bacteriology
Hfr strains of Escherichia coli K-12 were found capable of accepting a F'lac episome during mating, with a frequency approximating that of F(-) strains. However, the F'lac episome was unable to replicate in the Hfr cells, and was diluted out during the growth of the culture. The lac(+) gene of the episome can be 'rescued' by recombination into the host chromosome, as shown by the appearance of variegated recombinant colonies on a lactose-fermentation indicator medium. In recA Hfr strains, however, no lac(+) offspring were obtained in crosses with F'lac donors. The induced synthesis of beta-galactosidase in F'lac(+) x Hfr zygotes was studied. Rates of enzyme synthesis were approximately constant with respect to time as expected from unilinear inheritance of the F'lac episome. However, the rate of synthesis eventually increased, presumably due to integration of the lac(+) gene in some of the zygotes. In F'lac(+) x recA Hfr zygotes the rate of beta-galactosidase synthesis remained constant with respect to time, as expected
— id: 77987, year: 1968, vol: 95, page: 531, stat: Journal Article,

Studies on the mechanism of repression of arginine biosynthesis in Escherichia coli. 3. Repression of enzymes of arginine biosynthesis in arginyl-tRNA synthetase mutants
Hirshfield, I N; Horn, P C; Hopwood, D A; Maas, W K; DeDeken, R
1968 Jul 14;35(1):83-93, Journal of molecular biology
— id: 77986, year: 1968, vol: 35, page: 83, stat: Journal Article,

Inhibition of Escherichia coli B by homoarginine
Peyru, G M; Maas, W K
1967 Sep;94(3):712-718, Journal of bacteriology
Homoarginine inhibits the growth of Escherichia coli B, but not of E. coli K-12. These two strains also differ in regard to repressibility of the arginine-forming enzymes. In K-12, arginine acts as a repressor whereas in B it does not. The latter difference is determined by different alleles of a regulator gene, arg R. In K-12 x B crosses, it was shown that the genetic determinant for homoarginine sensitivity is closely linked to or identical with arg R. Homoarginine-resistant mutants of B were isolated. The biochemical mechanism of homoarginine inhibition is not known. However, whether or not a strain is sensitive to homoarginine seems to depend on the intracellular level of arginine. In B this level is relatively low and inflexible as a result of the action of a repressor whose formation is determined by the B-specific allele of arg R
— id: 77988, year: 1967, vol: 94, page: 712, stat: Journal Article,

Inducible system for the utilization of beta-glucosides in Escherichia coli. II. Description of mutant types and genetic analysis
Schaefler, S; Maas, W K
1967 Jan;93(1):264-272, Journal of bacteriology
Two types of mutants obtained by treating beta-gl(+) cells with nitrosoguanidine are described. One type, beta-gl(+)c, is constitutive for the biosynthesis of the aryl beta-glucoside splitting enzyme(s) and for the beta-glucoside permease; the other (beta-gl(+)sal(-)) has lost the capacity to ferment salicin, but has retained the capacity to ferment arbutin and other aryl beta-glucosides. By two successive mutational steps, beta-gl(+)sal(-)c double mutants can be obtained. Determinations of the enzymatic splitting of salicin and p-nitrophenyl beta-glucoside by beta-gl(+)sal(-) cells and extracts showed that these mutants have lost the capacity to split salicin but do split p-nitrophenyl beta-glucoside; they possess the beta-glucoside permease, and in them salicin is a gratuitous inducer for enzyme and permease biosynthesis. Studies on a beta-gl(+) strain, which splits salicin as well as p-nitrophenyl beta-glucoside, have shown that the splitting of salicin is more temperature-sensitive than that of p-nitrophenyl beta-glucoside and other beta-glucosides. Other properties of the two activities are similar. Interrupted mating experiments and cotransduction with P1kc phage showed that the genetic determinants of the beta-glucoside system map between the pyrE and ile loci. Three distinct mutational sites were found and are presumed to have the following functions: beta-glA, a structural gene for an aryl beta-glucoside splitting enzyme; beta-glB, either the structural gene for the beta-glucoside-permease or a regulatory gene; and beta-glC, a regulatory gene (or site). Escherichia coli wild-type strains are of the genotype A(+) B(-) C(+). The beta-gl(+) mutation determining the ability to ferment beta-glucosides is considered to be a permease or regulatory mutation, and the resulting genotype is A(+) B(+) C(+). The beta-gl(+)sal(-) phenotype results from a mutation in the beta-glA gene (genotype A' B(+) C(+)), and the constitutive phenotype results from a mutation in the beta-glC gene, the genotypes A(+) B(+)C(a) and A' B(+)C(a) corresponding to the phenotypes beta-gl(+)c and beta-gl(+)sal(-)c
— id: 77989, year: 1967, vol: 93, page: 264, stat: Journal Article,

Genetic defects affecting an arginine permease and repression of arginine synthesis in Escherichia coli
Maas, W K
1965 Sep-Oct;24(5):1239-1242, Federation Proceedings (Federation of American Societies for Experimental Biology)
— id: 77990, year: 1965, vol: 24, page: 1239, stat: Journal Article,

STUDIES ON THE MECHANISM OF REPRESSION OF ARGININE BIOSYNTHESIS IN ESCHERICHIA COLI. II. DOMINANCE OF REPRESSIBILITY IN DIPLOIDS
MAAS, W K
1964 Mar;8:365-370, Journal of molecular biology
— id: 77991, year: 1964, vol: 8, page: 365, stat: Journal Article,

STUDIES ON THE MECHANISM OF REPRESSION OF ARGININE BIOSYNTHESIS IN ESCHERICHIA COLI. I. DOMINANCE OF REPRESSIBILITY IN ZYGOTES
MAAS, W K; MAAS, R; WIAME, J M; GLANSDORFF, N
1964 Mar;8:359-364, Journal of molecular biology
— id: 77992, year: 1964, vol: 8, page: 359, stat: Journal Article,

GENETIC ASPECTS OF METABOLIC CONTROL
MAAS, W K; MCFALL, E
1964 ;18:95-110, Annual review of microbiology
— id: 77993, year: 1964, vol: 18, page: 95, stat: Journal Article,

Feedback inhibition of acetylglutamate synthetase by arginine in Escherichia coli
VYAS, S; MAAS, W K
1963 Mar;100:542-546, Archives of biochemistry & biophysics. ABB
— id: 77994, year: 1963, vol: 100, page: 542, stat: Journal Article,

Introduction of a gene from Escherichia coli B into HFR and F-strains of Escherichia coli K-12
MAAS, R; MAAS, W K
1962 Nov 15;48:1887-1893, Proceedings of the National Academy of Sciences of the United States of America
— id: 77995, year: 1962, vol: 48, page: 1887, stat: Journal Article,

Studies on repression of arginine biosynthesis in Escherichia coli
MAAS, W K
1961 ;26:183-191, Cold Spring Harbor symposia on quantitative biology
— id: 77996, year: 1961, vol: 26, page: 183, stat: Journal Article,

Control by endogenously synthesized arginine of the formation of ornithine transcarbamylase in Escherichia coli
NOVICK RP; MAAS WK
1961 Feb;81:236-240, Journal of bacteriology
— id: 64021, year: 1961, vol: 81, page: 236, stat: Journal Article,

Analysis of the inhibition of growth produced by canavanine in Escherichia coli
SCHWARTZ, J H; MAAS, W K
1960 Jun;79:794-799, Journal of bacteriology
— id: 77997, year: 1960, vol: 79, page: 794, stat: Journal Article,

An impaired concentrating mechanism for amino acids in mutants of Escherichia coli resistant to L-canavanine and D-serine
SCHWARTZ JH; MAAS WK; SIMON EJ
1959 Apr;32:582-583, Biochimica & biophysica acta
— id: 63725, year: 1959, vol: 32, page: 582, stat: Journal Article,

The potential for the formation of a biosynthetic enzyme in Escherichia coli
GORINI, L; MAAS, W K
1957 Jul;25(1):208-209, Biochimica & biophysica acta
— id: 77998, year: 1957, vol: 25, page: 208, stat: Journal Article,

Synthesis of pantothenic acid by depyrophosphorylation of adenosine triphosphate
MAAS, W K; NOVELLI, G D
1953 Mar;43(1):236-238, Archives of biochemistry & biophysics. ABB
— id: 78001, year: 1953, vol: 43, page: 236, stat: Journal Article,

Acetylation of Glutamic Acid by Extracts of Escherichia Coli
Maas, W K; Novelli, G D; Lipmann, F
1953 Oct;39(10):1004-1008, Proceedings of the National Academy of Sciences of the United States of America
— id: 77999, year: 1953, vol: 39, page: 1004, stat: Journal Article,

alpha-Ketoisovaleric acid, a precursor of pantothenic acid in Escherichia coli
MAAS, W K; VOGEL, H J
1953 Apr;65(4):388-393, Journal of bacteriology
— id: 78000, year: 1953, vol: 65, page: 388, stat: Journal Article,

Analysis of the Biochemical Mechanism of Drug Resistance in Certain Bacterial Mutants
Davis, B D; Maas, W K
1952 Sep;38(9):775-785, Proceedings of the National Academy of Sciences of the United States of America
— id: 78003, year: 1952, vol: 38, page: 775, stat: Journal Article,

Pantothenate studies, II. Evidence from Mutants for interference by salicylate with pantoate synthesis
MAAS, W K
1952 Feb;63(2):227-232, Journal of bacteriology
— id: 78005, year: 1952, vol: 63, page: 227, stat: Journal Article,

Pantothenate studies. III. Description of the extracted pantothenate-synthesizing enzyme of Escherichia coli
MAAS, W K
1952 Sep;198(1):23-32, Journal of biological chemistry
— id: 78004, year: 1952, vol: 198, page: 23, stat: Journal Article,

Production of an Altered Pantothenate-Synthesizing Enzyme by a Temperature-Sensitive Mutant of Escherichia Coli
Maas, W K; Davis, B D
1952 Sep;38(9):785-797, Proceedings of the National Academy of Sciences of the United States of America
— id: 78002, year: 1952, vol: 38, page: 785, stat: Journal Article,

Pantothenate studies. I. Interference by D-serine and L-aspartic acid with pantothenate synthesis in Escherichia coli
MAAS, W K; DAVIS, B D
1950 Dec;60(6):733-745, Journal of bacteriology
— id: 78006, year: 1950, vol: 60, page: 733, stat: Journal Article,

Spectrophotometric and Chromatographic Adsorption Analysis of the Red Eye Pigment of Drosophila Melanogaster
Maas, W K
1948 Mar;33(2):177-190, Genetics
— id: 78007, year: 1948, vol: 33, page: 177, stat: Journal Article,