Mutat Res, 1988 Oct, 206(2), 193 - 200 Study on the mutagenicity of nifurtimox and eight derivatives with the L-arabinose resistance test of Salmonella typhimurium; Alejandre-Duran E et al.; The mutagenicity of nifurtimox (nfx) and 8 nfx analogues has been investigated with the L-arabinose forward-mutation assay of Salmonella typhimurium . The nfx analogues tested were obtained by replacing the 3-methyl-4-yl-tetrahydro-1,4-thiazine-1,1-dioxide group of the parent compound with the following other groups: indazol-1-yl (1); pyrazol-1-yl (2); benzimidazol-1-yl (3); 1,2,4-triazol-4-yl (4); 1-methyl-3-methylthio-1,2,4-triazol-4-yl-5-thione (5); 3,5-bis(methylthio)-1,2,4-triazol-4-yl (6); 1-adamantyl (7); 4,6-diphenylpyridin-1-yl-2-one (8) . The mutagenic activity of each chemical was determined by the standard plate-incorporation test, in the presence or absence of the S9 activation mixture . The 9 compounds were mutagenic and exhibited linear dose-mutagenic response relationships . They were direct-acting mutagens and showed a nearly 1000-fold range in mutagenic potency from chemical 1 to nfx . In most cases, the addition of S9 mixture to the test plates decreased the mutagenicity of compounds . This effect was particularly noticeable in the case of chemicals 1-3, 5 and 7 where a more than 70% decrease in mutagenic activity was observed in the presence of the S9 mixture . The mutagenic potency of compounds in the Ara test showed a negative linear correlation with previously reported antitrypanosomal activity . Thus, chemicals 6 and 8 with in vitro activities against Trypanosoma cruzi clearly superior to that of nfx showed 2 of the lowest mutagenic potencies in the Ara test and these were only somewhat higher than the mutagenicity of the reference drug. Mutat Res, 1988 Oct, 206(2), 131 - 40 Mutagenic activities of selected nitrofluoranthene derivatives in Salmonella typhimurium strains TA98, TA98NR and TA98/1,8-DNP6; Zielinska B et al.; The mutagenic activities of novel nitrofluoranthene derivatives in Salmonella strains TA98, TA98NR and TA98/1,8-DNP6 (with and without S9 addition) are given . These derivatives were produced from the reactions of fluoranthene (FL) and its directly mutagenic 2- and 3-nitro derivatives with covalent dinitrogen pentoxide (N2O5) in CCl4 solution at ambient temperature . The influence of the addition of a nitro group on the observed activity of the resulting di- and tri-nitrofluoranthenes is discussed. Pediatr Res, 1988 Oct, 24(4), 508 - 11 The effect of postnatal development on the adherence of nonfimbriated and fimbriated Salmonella typhimurium to isolated small intestinal enterocytes; el Monem AM et al.; The adherence of radiolabeled fimbriated (S 7471 OF) and nonfimbriated (S 7471 N) Salmonella typhimurium to small intestinal rat enterocytes was examined during postnatal development . The fimbriated strain invariably adhered in higher numbers than the nonfimbriated strain during all periods of development . The capability of enterocytes to bind Salmonella increased significantly during postnatal development and reached adult levels at weaning time (21 days of age) . Bacterial adherence to enterocytes was similar if the cells were isolated from the proximal or the distal small intestine . Early weaning of pups did not affect the capability of enterocytes to bind Salmonella . Pretreatment of isolated enterocytes from adult animals with rat's milk before exposure to Salmonella had no effect on the level of bacteria that adhered per enterocyte . Conversely, pretreatment of Salmonella with rats' milk before binding to enterocytes from adult animals also did not alter the level of bacteria adhered per enterocyte . These results suggest an age-dependent, postnatal development of available receptors for S . typhimurium on rat enterocytes . The acquisition of these receptors is not affected by mother's milk and is unaltered by early weaning. Bioorg Khim, 1988 Oct, 14(10), 1419 - 27 {Incorporation of abequose residues into O-specific polysaccharides of Salmonella serotypes B, C2 and C3}; Druzhinina TN et al.; The possibility of chemical-enzymatic synthesis of O-specific polysaccharide and its modified derivatives was demonstrated with a cell envelope preparation from Salmonella typhimurium using synthetic polyprenyl pyrophosphate oligosaccharides and CDP-{14C}Abe . It was shown that during biosynthesis of O-specific polysaccharides from S . newport and S . kentucky abequosylation reaction occurs prior to polymerization of oligosaccharide repeating units. J Mol Biol, 1988 Sep 20, 203(2), 353 - 72 Structure and organization of Marchantia polymorpha chloroplast genome . IV . Inverted repeat and small single copy regions; Kohchi T et al.; We characterized the genes in the regions of large inverted repeats (IRA and IRB, 10,058 base-pairs each) and a small single copy (SSC 19,813 bp) of chloroplast DNA from Marchantia polymorpha . The inverted repeat (IR) regions contain genes for four ribosomal RNAs (16 S, 23 S, 4.5 S and 5 S rRNAs) and five transfer RNAs (valine tRNA(GAC), isoleucine tRNA(GAU), alanine tRNA(UGC), arginine tRNA(ACG) and asparagine tRNA(GUU)) . The gene organization of the IR regions in the liverwort chloroplast genome is conserved, although the IR regions are smaller (10,058 base-pairs) than any reported in higher plant chloroplasts . The small single-copy region (19,813 base-pairs) encoded genes for 17 open reading frames, a leucine tRNA(UAG) and a proline tRNA(GGG)-like sequence . We identified 12 open reading frames by homology of their coding sequences to a 4Fe-4S-type ferredoxin protein, a bacterial nitrogenase reductase component (Fe-protein), five human mitochondrial components of NADH dehydrogenase (ND1, ND4, ND4L, ND5 and ND6), two Escherichia coli ribosomal proteins (S15 and L21), two putative proteins encoded in the kinetoplast maxicircle DNA of Leishmania tarentolae (LtORF 3 and LtORF 4), and a bacterial permease inner membrane component (encoded by malF in E . coli or hisQ in Salmonella typhimurium). J Biol Chem, 1988 Sep 15, 263(26), 12986 - 93 Glucose permease of Escherichia coli . Purification of the IIGlc subunit and functional characterization of its oligomeric forms; Meins M et al.; The membrane subunit (IIGlc) of the glucose permease has been purified from overproducing Escherichia coli . About 2 mg of pure protein was obtained from 10 g (wet weight) of cells . IIGlc of E . coli and Salmonella typhimurium are functionally indistinguishable . A small difference was revealed, however, by a monoclonal antibody which neutralizes glucose phosphorylation activity of IIGlc from S . typhimurium, but does not cross-react with IIGlc of E . coli . A dimeric form of purified IIGlc can be detected by chemical cross-linking and by zonal sedimentation at 4 degrees C . Upon mild oxidation a disulfide bond is formed between the subunits of the dimer . Oxidized IIGlc is more stable than the reduced form but is inactive because it cannot be phosphorylated by the cytoplasmic subunit (IIIGlc) of the glucose permease . Cys-421 could be identified as the oxidation-sensitive residue, using a novel assay to detect IIIGlc-dependent phosphorylation of nitrocellulose-bound IIGlc that has been purified by gel electrophoresis . No dimeric form of phosphorylated IIGlc could be detected . Because phosphorylated IIGlc is a catalytic intermediate it is concluded that catalytically active IIGlc is a monomer and that the dimeric form is an artefact observed only with purified resting IIGlc . That IIGlc is active as a monomer is further supported by the observation that monomeric IIGlc catalyzes phosphoryl exchange between glucose and glucose 6-phosphate at equilibrium and that an excess of inactive IIGlc with a serine replacing Cys-421 does not interfere with the activity of wild-type IIGlc as would be expected if interaction between the subunits in a dimer were essential for activity. Eur J Biochem, 1988 Sep 15, 176(2), 421 - 9 Nucleotide sequence of the carA gene and regulation of the carAB operon in Salmonella typhimurium; Kilstrup M et al.; The carAB operon of Salmonella typhimurium encoding carbamoyl-phosphate synthetase (CPSase) has been cloned, and the nucleotide sequence of the first gene of the operon, carA, together with 760 base pairs of the 5'-flanking region was determined . The product of the carA gene is the small subunit of CPSase . It catalyzes the transfer of the amide group from glutamine to an NH3-site on the heavy subunit . Primer extension and S1 nuclease mapping of in vivo carAB transcripts revealed that transcription is similar to that of Escherichia coli {Piette, J . et al . (1984) Proc . Natl Acad . Sci . USA 81, 4134-4138} in its initiation at two promoters, P1 and P2, controlled by pyrimidines and arginine, respectively . The arginine control is mediated through binding to the arginine repressor (argR) . The involvement of titratable regulatory elements is indicated by the escape from both arginine and pyrimidine control, when the operon is present in multicopies on a plasmid . Measurements of CPSase levels in mutants which allows independent manipulation of the intracellular uracil and cytosine nucleotide pools show, that both uracil and cytosine nucleotides are required for full repression and that limitation of either nucleotide results in derepression of CPSase synthesis . Deletion analyses indicate that regions upstream of the P1 promoter are required for normal expression from this promoter but not from P2. Nucleic Acids Res, 1988 Sep 12, 16(17), 8207 - 11 Codon usage patterns in Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Drosophila melanogaster and Homo sapiens; a review of the considerable within-species diversity; Sharp PM et al.; The genetic code is degenerate, but alternative synonymous codons are generally not used with equal frequency . Since the pioneering work of Grantham's group it has been apparent that genes from one species often share similarities in codon frequency; under the "genome hypothesis" there is a species-specific pattern to codon usage . However, it has become clear that in most species there are also considerable differences among genes . Multivariate analyses have revealed that in each species so far examined there is a single major trend in codon usage among genes, usually from highly biased to more nearly even usage of synonymous codons . Thus, to represent the codon usage pattern of an organism it is not sufficient to sum over all genes as this conceals the underlying heterogeneity . Rather, it is necessary to describe the trend among genes seen in that species . We illustrate these trends for six species where codon usage has been examined in detail, by presenting the pooled codon usage for the 10% of genes at either end of the major trend . Closely-related organisms have similar patterns of codon usage, and so the six species in Table 1 are representative of wider groups . For example, with respect to codon usage, Salmonella typhimurium closely resembles E . coli, while all mammalian species so far examined (principally mouse, rat and cow) largely resemble humans. Mutat Res, 1988 Sep, 201(1), 181 - 8 Mutagenic and carcinogenic heterocyclic amines in Chinese cooked foods; Zhang XM et al.; Samples of 7 foods commonly eaten in the Northeast of China (i.e . fried and broiled fishes and broiled meat) were tested for mutagenicity on Salmonella typhimurium TA98 with S9 mix . The basic fractions of the samples were mutagenic, inducing 33-2930 revertants/g of cooked food . Fried walleye pollack (a kind of cod fish heated on a stainless steel pan) showed the highest mutagenicity, so attempts were made to isolate mutagens from the basic fraction of this food . The mutagens were purified by treatment with blue cotton and HPLC on a semi-preparative ODS column and analytical cation exchange and ODS columns . 5 mutagens were isolated and identified as 2-amino-3-methylimidazo{4,5-f}quinoline (IQ), 2-amino-3,4-dimethylimidazo{4,5-f}quinoline (MeIQ), 2-amino-3,8-dimethylimidazo{4,5-f}quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo{4,5-f}quinoxaline (4,8-DiMeIQx) and 2-amino-1-methyl-6-phenylimidazo{4,5-b}pyridine (PhIP) . 1 g of fried fish was estimated to contain 0.16 ng of IQ, 0.03 ng of MeIQ, 6.44 ng of MeIQx, 0.10 ng of 4,8-DiMeIQx and 69.2 ng of PhIP . MeIQx and PhIP accounted for 24% and 4.7%, respectively, of the total mutagenicity . The other 3 heterocyclic amines were each responsible for only 0.3-1.2% of the total mutagenicity. Food Chem Toxicol, 1988 Sep, 26(9), 791 - 6 N,N-diethylphenylacetamide, an insect repellent: absence of mutagenic response in the in vitro Ames test and in vivo mouse micronucleus test; Meshram GP et al.; N,N-diethylphenylacetamide (DEPA), a promising new insect repellent, was tested for mutagenicity in the in vitro Ames Salmonella/microsome mutagenicity test and the in vivo mouse micronucleus test . For the Ames test, DEPA was assayed both in the presence and absence of Aroclor 1254-induced rat-liver S-9 mix (5 and 20% S-9 fraction), using five tester strains of Salmonella typhimurium--TA97a, TA98, TA100, TA102 and TA104 . For the micronucleus test, mice were exposed to DEPA through ip injection for 2 and 5 days in separate experiments, and bone marrow and peripheral blood were sampled 6 and 48 hr after the final injection, respectively . DEPA did not induce a mutagenic response in the Ames test, and mouse bone marrow and peripheral blood micronucleus tests . DEPA was not considered cytotoxic, as a depression of the percentage PCE was not observed at any dose in the range of 1 to 100 mg/kg body weight with either treatment protocol of the micronucleus test. Res Vet Sci, 1988 Sep, 45(2), 240 - 50 Pathology of calves with diarrhoea in southern Britain; Hall GA et al.; Twenty-one moribund calves with diarrhoea were purchased from 11 farms, their faeces examined for enteropathogens and samples of intestinal tissue removed under anaesthesia . Lesions and presence of enteropathogens on the mucosal surface were scored by histological examination of immunostained paraffin sections . Two or more enteropathogens were detected in 19 calves . Cryptosporidium appeared to be the principal cause of diarrhoea in six calves, rotavirus in four, Salmonella typhimurium in two, bacteria adherent to the surface of the large intestine in two, coronavirus in one and K99+ Escherichia coli in one calf . Diarrhoea in four calves was the consequence of mixed infections in which no one enteropathogen appeared to predominate . In one calf no enteropathogen was detected . Diarrhoea was associated with infections and lesions throughout the small and large intestines . The enteropathogens most frequently associated with lesions in the small intestines were rotavirus, coronavirus and cryptosporidium; in the large intestines they were coronavirus and bacteria apparently adherent to the mucosal surface. Mutagenesis, 1988 Sep, 3(5), 381 - 7 Concentrated drinking water extracts, which cause bacterial mutation and chromosome damage in CHO cells, do not induce sex-linked recessive lethal mutations in Drosophila; Wilcox P et al.; Concentrated extracts prepared from chlorinated drinking water samples were tested for their ability to induce sex-linked recessive lethal mutations in Drosophila melanogaster . Adult flies were allowed to feed on sucrose solutions prepared using neat or half-strength water extract . The drinking water extracts used for this study were also tested in bacterial fluctuation assays using Salmonella typhimurium TA100 and TA98 and in an in vitro cytogenetic assay using CHO cells . Although the water extracts gave positive results in both of these in vitro tests, there was no evidence of mutagenic activity in the Drosophila studies. Mol Gen Genet, 1988 Sep, 214(1), 32 - 6 Salmonella typhimurium LT2 metF operator mutations; Stauffer GV et al.; Using an Escherichia coli lac deletion strain lysogenized with lambda phage carrying a metF-lacZ gene fusion (lambda Flac), in which beta-galactosidase levels are dependent on metF gene expression, cis-acting mutations were isolated that affect regulation of the Salmonella typhimurium metF gene . The mutations were located in a region previously defined as the metF operator by its similarity to the E . coli metF operator sequence . Regulation of the metF gene was examined by measuring beta-galactosidase levels in E . coli strains lysogenized with the wild-type lambda Flac phage and mutant lambda Flac phage . The results suggest that the mutations disrupt the methionine control system mediated by the metJ gene product, but not the vitamin B12 control system mediated by the metH gene product . The results also demonstrate that negative control of the metF gene by the metH gene product and vitamin B12 is dependent on a functional metJ gene product. Food Chem Toxicol, 1988 Sep, 26(9), 745 - 52 Reduction of mutagenicity and toxicity of aflatoxin B1 by chlorine gas treatment; Sen AC et al.; Chlorine gas was used to treat aflatoxin B1 (AFB1) . The time-related exposure study showed that 4 ml (15 mg) pure chlorine gas caused about 90% destruction of 100 micrograms AFB1 within 10 min, at standard temperature and pressure . Four fluorescent reaction products were produced, two of which were identified as 8,9-dichloro-AFB1 and 8,9-dihydroxy-AFB1 (diol) . The use of {14C}AFB1 confirmed the 90% destruction of the compound by chlorine gas . An increased destruction of AFB1 also occurred when an increased amount of chlorine gas was used . The mutagenic activity of the AFB1 sample treated for 10 min was reduced to about 5% of the untreated control using the Salmonella typhimurium strain TA98 in the presence of a rat-liver S-9 mix . A similar time-related reduction in AFB1 toxicity after chlorine treatment was also achieved using the chicken embryo toxicity assay. Mutat Res, 1988 Sep, 201(1), 241 - 51 Base-change analysis of revertants of the hisD3052 allele in Salmonella typhimurium; Fuscoe JC et al.; This report is an investigation of the specific sequence changes in the DNA of Salmonella hisD3052 revertants induced by a set of specific frameshift mutagens found in our diet . They include B{a}P, aflatoxin B1, and the cooked-food mutagens, IQ, MeIQ, and PhIP . The Salmonella DNA was cleaved with restriction enzymes Sau3A, EcoR1, and Alu1 to give a 620-bp fragment containing the hisD3052 site . The size-fractionated fragments were ligated to the bacteriophage vector M13mp8 . After transformation into E . coli, the recombinants were screened with a nick-translated hisD+ gene probe, and the isolated single-stranded DNA was sequenced . All IQ (13), MeIQ (3), PhIP (5), and aflatoxin B1 (3) induced revertants isolated had a 2-base (-CG- dinucleotide) deletion situated 10 bases upstream from the original hisD3052 -C- deletion . In contrast, 9 of 24 revertants induced by B{a}P had extensive deletions varying from 8 to 26 nucleotides in length and located at various sites along a 45-base-pair sequence beginning at nucleotide 2085 of the his operon . The other 15 B{a}P-induced revertants had a -CG- deletion at the same location as the revertants induced by the other food mutagens . 7 spontaneous revertants were also analyzed; they showed 3 -CG- deletions, 1 insertion and 3 distinct deletions (varying from 2 to 11 bases in size) . In total, 13 distinct base changes are described which lead to reversion of the hisD3052 mutation. Infect Immun, 1988 Sep, 56(9), 2324 - 9 Effect of small cationic leukocyte peptides (defensins) on the permeability barrier of the outer membrane; Viljanen P et al.; Defensins are small cationic antibacterial peptides that are abundant in polymorphonuclear leukocytes from human and other sources (T . Ganz, M . Selsted, D . Szklarek, S . Harwig, K . Daher, D . F . Bainton, and R . J . Lehrer, J . Clin . Invest . 76:1427-1435, 1985) . We studied whether subinhibitory concentrations of defensins increase the outer membrane (OM) permeability of Escherichia coli, Salmonella typhimurium, and Pseudomonas aeruginosa to hydrophobic probes, as do many other polycations that have been studied previously . Throughout the study, we used polymyxin B nonapeptide (PMBN) as a reference peptide . PMBN has a known potent OM permeability-increasing action . As a sharp contrast to PMBN, subinhibitory concentrations of defensins did not permeabilize (or, under some test conditions, permeabilized very slightly) the OM to the probes that were used (rifampin and Triton X-100) . At bacteriostatic or bactericidal defensin concentrations, some degree of synergism with rifampin was seen. J Gen Microbiol, 1988 Sep, 134 ( Pt 9), 2535 - 41 Bacteriophage X-2: a filamentous phage lysing IncX-plasmid-harbouring bacterial strains; Coetzee JN et al.; Phage X-2, a filamentous rod about 950 nm in length, was isolated from sewage as plating on strains of Escherichia coli, Salmonella typhimurium or Serratia marcescens carrying either the IncX plasmid R6K, or the unique plasmid R775 . Phage X-2 differs morphologically from a previously described very broad host range filamentous phage X which also lyses plasmid R6K-carrying strains and the phages differ in their resistance to inactivation by diethyl ether . Phage X-2 is serologically unrelated to phage X and the X-like phages IKe and I2-2 . The adsorption site of the phage on the plasmid-bearing strains could not be determined but evidence implicating conjugative pili is presented. Mutagenesis, 1988 Sep, 3(5), 423 - 7 Caffeine inhibits hepatic-microsomal activation of some dietary genotoxins; Alldrick AJ et al.; Hepatic microsomal fractions (microsomes) were prepared from female BALB/c mice . The potential of caffeine to modify the ability of microsomes to convert the heterocyclic aromatic amines MeIQ, Trp-P-2 and MeIQx, to bacterial mutagens (indicator: Salmonella typhimurium TA98) was investigated . Caffeine inhibited mutagenicity and did so by inhibiting microsomal metabolism of the three compounds, rather than by altering uptake of the active mutagens and/or interacting with the DNA repair processes in the bacterial cell . Notional Ki values determined for the three heterocyclic amines were similar, suggesting that caffeine inhibits at a stage common to the metabolism of all three compounds. Br Poult Sci, 1988 Sep, 29(3), 521 - 9 Genetics of resistance to Salmonella typhimurium in newly hatched chicks; Bumstead N et al.; 1 . A survey of inbred and partially inbred lines of chickens showed pronounced differences in mortality following challenge of the newly hatched chicks with Salmonella typhimurium . Lines W, 6(1) and N were highly resistant to challenge, whereas lines C and 15I were highly susceptible . 2 . This difference in susceptibility was observed with a range of 5 strains of S . typhimurium of different degrees of virulence and also following both oral and intramuscular challenge . 3 . The inheritance of resistance was studied in detail by examining a series of crosses between the susceptible line C and resistant line W . The pattern of mortality in crosses and back-crosses between these lines indicated resistance is dominant and was consistent with the inheritance of a dominant autosomal resistance gene . 4 . There was no evidence of maternal effects in these crosses, and no evidence of association with the major histocompatability complex. Zh Mikrobiol Epidemiol Immunobiol, 1988 Sep, (9), 28 - 33 {The role of the aggregation of microbial cells in the development of salmonellosis in mice}; Zhalko-Titarenko VP et al.; The dependence of the invasive action of Salmonella typhimurium in mice on the aggregation of microbial cells has been studied in vivo, as well as in vitro on explanted intestinal tissue . The aggregation of salmonellae on kaolin grains has been found to lead to an increase in the level of adhesion of salmonellae to the intestinal mucosa of mice in vitro, to the accelerated course of infection in mice and their death and to the increased contamination of the spleen . The data obtained in these experiments age indicative of the possibility of the adverse influence of some sorbents on the course of the infectious process and confirm the concept advanced by the authors on the major importance of the surface concentration of salmonellae on the mucous membrane for the effectiveness of contamination. Sangyo Igaku, 1988 Sep, 30(5), 385 - 91 {Comparative study on the mutagenic activity of rat liver and bladder S9 by fluctuation test}; Hayashi K et al.; Mutagenicity of seven aromatic amines, two heterocyclic amines, two azo compounds and one polycyclic aromatic hydrocarbon was examined with a fluctuation test modified by Gatehouse . The test was performed by using Salmonella typhimurium TA98 in the presence of liver and bladder S9 from PCB pretreated rats . Seven out of 12 compounds showed mutagenic activities with liver S9 and seven with bladder S9 . Benzidine, 3-methylcholanthrene and 2-acetylaminofluorene showed a negative response with bladder S9 but a positive response with liver S9 . The mutagenicity of the seven compounds observed with bladder S9 had a lower sensitivity than with liver S9 . 3-Amino-1,4-dimethyl-5H-pyrido{4,3-b}indole and 3-amino-1-methyl-5H-pyrido{4,3-b}indole showed mutagenic activity at lower concentrations than the other compounds which showed mutagenic activity either with bladder S9 or liver S9 . Mutagenicity of 3-methylcholanthrene was observed at high concentration only in the presence of liver S9 . The findings from the present study suggested that aromatic amines, heterocyclic amines and polycyclic aromatic hydrocarbons were more likely to be activated to strong mutagens with liver S9 than with bladder S9. J Nat Prod, 1988 Sep-Oct, 51(5), 866 - 73 Plant antimutagenic agents, 1 . General bioassay and isolation procedures; Wall ME et al.; An antimutagenic assay in Salmonella typhimurium has been utilized for a study of the inhibition of the mutagenic activity of 2-aminoanthracene in the presence of the Ames S-9 metabolic activation preparation by crude organic solvent extracts of plant materials . More than 2000 extracts representing 39 families have been tested to date . Confirmed inhibitory activity has been found in 80 samples . More than 60% were nontoxic . Methods for isolation and characterization of pure compounds are presented . Of particular interest is the utilization of large scale preparative hplc for rapid purification of inhibitory chromatographic fractions that were still highly impure. Mol Biol Evol, 1988 Sep, 5(5), 531 - 48 Evolution of aminobenzoate synthases: nucleotide sequences of Salmonella typhimurium and Klebsiella aerogenes pabB; Goncharoff P et al.; p-Aminobenzoate synthase (PS) and anthranilate synthase (AS) are structurally related enzymes that catalyze similar reactions and produce similar products, para- and ortho-aminobenzoate (anthranilate) . Each enzyme is composed of two non-identical subunits: a glutamine amidotransferase subunit (CoII) and a subunit that produces an aminobenzoate product (CoI) . Nucleotide sequence comparisons of the Escherichia coli genes encoding each of the subunits suggest a common evolutionary origin for both subunits of the enzyme complexes . We report here the nucleotide sequences of the pabB genes that encode Salmonella typhimurium and Klebsiella aerogenes PS CoI . Comparative sequence information suggests that pabB is encoded as the first gene in a multicistronic transcript . Comparison of deduced amino acid sequences of PS CoI genes indicates that the majority of sequence identity occurs in the C-terminal two-thirds of the proteins . Similarly, identities in an alignment of eight PS and AS CoI sequences are confined to the C-terminal segments of the proteins . Secondary-structure predictions for the nine sequences suggest considerable similarity in the folding of the C-terminal portions of the aminobenzoate synthases. Mutat Res, 1988 Sep-Oct, 209(1-2), 67 - 74 Relationships between structure of nitrated arenes and their mutagenicity in Salmonella typhimurium; 2- and 2,7-nitro substituted fluorene, phenanthrene and pyrene; Hirayama T et al.; In order to elucidate the mechanisms of mutagenic activation of nitroarenes, we studied the relationships between the mutagenic potency and chemical structure of 2-nitro- and 2,7-dinitro-arenes including nitrated fluorene (Fl), dihydrophenanthrene (DHPh), phenanthrene (Ph), tetrahydropyrene (THPy), dihydropyrene (DHPy) and pyrene (Py) together with 9-NO2-Ph, 1-NO2-Py and 1.3-diNO2-Py . The mutagenicity tests were carried out on Salmonella typhimurium TA98, TA98NR and TA98/1,8-DNP6 in the absence of S9 mix . The order of mutability of mononitro- and dinitro-arenes in TA98 is as given below: 2-NO2-THPy less than 2-NO2-Fl less than 2-NO2-DHPh less than 9-NO2-Ph less than 2-NO2-Ph less than 2-NO2-DHPy less than 1-NO2-Py less than 2-NO2-Py, and 2,7-diNO2-DHPh less than 2,7-diNO2-Fl less than 2,7-diNO2-THPy less than 2,7-diNO2-Ph less than 2,7-diNO2-DHPy less than 2,7-diNO2-Py less than 1,3-diNO2-Py . 9-NO2-Ph and 1-NO2-Py, which have been detected in environmental samples, are not as potent mutagens as 2-nitrated phenanthrene and pyrene, respectively . 2-NO2THPy (37.7 rev/nmole) was a weak mutagen, but 2,7-diNO2-THPy (3197 rev/nmole) was as potent a mutagen as 2,7-diNO2 (3925 rev/nmole) . Tetrahydropyrene has a twisted form in its structure . 1,3-diNO2-Py (99660 rev/nmole) was more mutagenic than 2,7-diNO2-Py (37960.0 rev/nmole), and their mutagenicities were correlated with the behavior of the K-band in their UV spectra by the introduction of nitro groups on pyrene. Mutat Res, 1988 Sep, 201(1), 89 - 96 Study of the causes of direct-acting mutagenicity in coffee and tea using the Ara test in Salmonella typhimurium; Ariza RR et al.; The mutagenic activities of 6 of the chemicals identified in coffee solutions were assayed with the Salmonella Ara test, under experimental conditions optimized for coffee mutagenicity . Caffeine was the only non-mutagenic compound . Among the other 5 chemicals, hydrogen peroxide was the strongest mutagen and chlorogenic acid the weakest; methylglyoxal, glyoxal and caffeic acid exhibited intermediate mutagenicities . The minimal mutagenic doses of these components correlated negatively with their relative concentrations in coffee . It was concluded that chlorogenic acid, caffeic acid, glyoxal and methylglyoxal cannot contribute alone to the mutagenicity of coffee in the Ara test, since their minimal mutagenic concentrations were much higher than their respective levels in the coffee samples assayed . By contrast, 40-60% of the mutagenic activity in coffee and also in tea could be attributed to their H2O2 contents . Catalase abolished more than 95% of the mutagenic activity of coffee, as detected by the Ara test . A similar sensitivity to catalase has been reported by other authors in relation to the coffee mutagenicity identified by the Salmonella His test . Nevertheless, the results presented in this paper suggest that the Ara forward and the His reverse mutation tests are sensitive to the mutagenicity of different constituents in coffee solutions . We propose that the His test, sensitive at high coffee doses, mainly recognizes the mutagenicity of methylglyoxal, whilst the Ara test, sensitive at low coffee doses, mainly detects the mutagenic activity of hydrogen peroxide . The data reported also suggest that the direct-acting mutagenicity(ies) detected by the Ara test in tea solutions is (are) based on similar, if not identical, mechanisms. Mutat Res, 1988 Sep, 201(1), 189 - 94 Phenotypic and reversion analysis of a Salmonella typhimurium constructed to have an arginine codon at the hisG46 missense codon; Miller JK et al.; Of the 6 single-base mutations that would be predicted to change the missense mutation hisG46 away from a proline codon in the Salmonella/microsome mutagen selection assay for histidine-independent revertants, only 5 have been observed . We have used site-specific mutagenesis to make the unobserved mutant {CCC (proline)----CGC (arginine)} codon in the Salmonella genome . Experiments with this arginine mutant demonstrate that, like bacteria containing the hisG46 mutation, bacteria with the arginine missense mutation are histidine auxotrophs which are capable of reversion to histidine independence . However, unlike the ATP phosphoribosyltransferase coded by the hisG46 his G gene (with a proline), the arginine mutant enzyme is partially active . This is indicated by a histidine-independent phenotype when the arginine hisG gene is present in multiple copies. Mutat Res, 1988 Sep, 201(1), 127 - 36 Pure exogenous singlet oxygen: nonmutagenicity in bacteria; Dahl TA et al.; Singlet oxygen (1 delta gO2) is the lowest energy-excited state of molecular oxygen, and more reactive than the triplet ground-state molecule . Although singlet oxygen has been implicated in a variety of biological effects, including reactions with DNA or some of its components, evidence for mutagenesis by singlet oxygen has remained unclear . We have previously described a system for bacterial exposure to pure exogenous singlet oxygen that eliminates ambiguity regarding the identity of the reactive species responsible for observed results . Despite the potent toxicity of pure singlet oxygen for several different strains of bacteria, we have found no evidence for mutagenicity of singlet oxygen in 26 Salmonella typhimurium histidine-auxotrophic strains killed to 35% survival . These strains included a variety of base-pair substitution or frameshift target sequences for reversion, including targets responsive to oxidative damage and targets rich in GC base pairs . Some strains combined histidine mutations with one or more mutations affecting DNA-repair capacity . 4 strains possessing the hisG46 mutation also were not mutated when exposed to dose ranges killing less than 28% and up to 99% of the bacteria . The relative frequency of small inphase deletions was assayed in hisG428 bacteria exposed to single oxygen and found to be the same as the spontaneous level . In addition to lack of induction of mutation in these strains, the 8-azaguanine forward mutation assay yielded no evidence of mutagenesis by singlet oxygen in strains killed to 15% survival . No induction of genetic changes by singlet oxygen was seen in an assay for duplication of approximately 1/3 of the bacterial chromosome . Tests for the ability of singlet oxygen to induce lambda prophage in E . coli K12 also proved negative . These studies collectively indicate that pure singlet oxygen generated outside the bacterial cell does not react significantly with the bacterial chromosome in ways leading to base-pair substitutions, frameshift mutations, small or large deletions, large duplications, or damage that interferes with DNA replication and induces the SOS system. Mutat Res, 1988 Sep, 201(1), 117 - 26 N-nitroso-N-2-fluorenylacetamide: a new direct-acting mutagen and teratogen; Lin JK et al.; Reaction of N-2-fluorenylacetamide (2-FAA, CAS No . 53-96-3) with nitrous fume (N2O3) in glacial acetic acid at 0 degree C yields N-nitroso-N-2-fluorenylacetamide (N-NO-2-FAA), 3-nitro-N-2-fluorenylacetamide, N-nitroso-3-nitro-N-2-fluorenylacetamide and other compounds . N-NO-2-FAA is the major product (80%) and fairly stable at low temperature (-20 degrees C), but extremely labile at ambient temperature . The chemical structure of N-NO-2-FAA is characterized by spectrometric analysis of its naphthol coupling derivatives . This new compound is highly mutagenic to Salmonella typhimurium TA97, TA98, TA100 and TA1538 and requires no microsomal metabolic activation . The mutagenicity of N-NO-2-FAA in TA98 is higher than that of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG, CAS No . 70-25-7) and N-acetoxy-N-2-fluorenylacetamide (N-AcO-2-FAA) . The teratogenic potential of N-NO-2-FAA was studied with white Leghorn chick embryos given a single dose of 1-100 micrograms/egg on day 6 of incubation . A high incidence of flaccid paralysis of the legs and a low incidence of feather, claw and bill malformations were found in the treated group; no such malformed embryos were found in the control group . The teratogenicity of N-NO-2-FAA was found to be weaker than that of MNNG, but comparable to that of N-methyl-N-nitrosourea (CAS No . 684-93-5) . N-NO-2-FAA is a strong electrophile and reacts readily with histidine, lysine, cysteine, glutathione, tryptophan, adenosine, cytidine at neutral pH . In contrast to N-AcO-2-FAA, N-NO-2-FAA does not react significantly with guanosine and thymidine . It seems that N-NO-2-FAA is a strong direct-acting mutagen and probably a new prototype of synthetic carcinogen. Mutat Res, 1988 Sep, 206(1), 65 - 71 Mutagen formed from tryptophan reacted with sodium nitrite in acidic solution; Ohara A et al.; The reaction products from L-tryptophan treated with nitrite under acidic conditions were investigated for mutagenic activity with the Salmonella typhimurium his reversion assay and for DNA-damaging activity using the rec-assay . The diethyl ether extract of the reaction mixture showed 8 spots on thin-layer chromatography (TLC) . One compound from the TLC had high mutagenic activity for TA98 without S9 mix, with little DNA-damaging activity . The mutagen was purified and identified by instrumental analysis as 2-hydroxy-(1-N-nitrosoindole)propionic acid (NIHP) . The mutagenic activity of NIHP was determined by the induced mutation frequency method; the induced mutation frequency was about 19.2 X 10(-5) at a dose level of 160 micrograms/plate. Mutat Res, 1988 Sep, 206(1), 55 - 63 Induction of chromosomal aberrations in rat bone marrow cells and mutations in Salmonella typhimurium by benz{a}anthracene derivatives; Ito Y et al.; Benz{a}anthracene (BA) and its derivatives containing methyl and/or ethyl groups in the 7 and/or 12 positions were tested for their ability to induce chromosome aberrations (CA) in rat bone marrow cells and for their mutagenicity to Salmonella typhimurium TA100 or TA98 . The incidence of aberrant cells induced by the BA derivatives, given in lipid emulsion as a single-pulse dose of 50 mg/kg body weight into the caudal vein, was in the order: DMBA greater than EMBA greater than MEBA greater than other BA derivatives = control . The alkyl groups, at least 1 methyl group, at the 7 and 12 positions of BA seemed to be necessary to induce CA, although DEBA having ethyl groups at both the 7 and 12 positions of BA did not induce CA . DMBA or EMBA induced not only gaps and breaks but also exchanges and multiple CA, while the CA induced by other BA derivatives consisted of only gaps and breaks . 7MBA and 12MBA which exhibit carcinogenic activity intermediate between that of DMBA and BA induced few CA in the present system . However, the correlation coefficient between the logarithm incidence of aberrant cells and the carcinogenicity index calculated from the data of 9 BA derivatives including both 7MBA and 12MBA was 0.792 . The relative mutagenicities of the BA derivatives with TA100 in the presence of hepatic S9 from polychlorinated biphenyl (PCB)-treated rats were in the order: BA greater than 7MBA greater than DMBA greater than 12MBA greater than 7EBA greater than EMBA greater than MEBA greater than 12EBA = DEBA = control . The results with TA98 were essentially the same as those with TA100 . The results with TA100 in the presence of hepatic S9 from phenobarbital (PB)-treated rats were in the order: DMBA greater than 12MBA greater than 7MBA greater than 7EBA greater than BA greater than EMBA = MEBA greater than 12EBA = DEBA = control . These findings reveal no obvious relation between the mutagenic activities of the BA derivatives with the PCB-S9 or PB-S9 activating systems and their capacities to induce CA or their reported carcinogenicities . The incidence of CA induced by the dihydrodiols implicated as the metabolic precursors of the active diol epoxide metabolites of several of these BA derivatives was also tested . BA 3,4-dihydrodiol, like BA itself, induced few CA . However, the corresponding dihydrodiols of DMBA, 12MBA and 7MBA, induced relatively high levels of CA.(ABSTRACT TRUNCATED AT 400 WORDS) Mutat Res, 1988 Sep, 206(1), 41 - 6 Genetic toxicology evaluation of commercial beers . II . Mutagenic activity of commercial beer products in Salmonella typhimurium strains TA98, TA100 and TA102; Brusick DJ et al.; 5 concentrated extracts of commercial beers were prepared using XAD-2 resin . The residues were subjected to evaluation for mutagenic activity in Salmonella typhimurium strains TA98, TA100 and TA102 . The tests were conducted using preincubation protocols including provisions for S9 metabolic activation . Although the extracts did produce moderate toxicity to the Salmonella organisms used in the assays, none of the residues were found to induce mutation up to their maximum testable concentrations. Mutat Res, 1988 Sep, 206(1), 115 - 25 Mutagenicity of aromatic glycidyl ethers with Salmonella; Rosman LB et al.; 6 aromatic glycidyl ethers containing naphthyl, biphenyl or benzylphenyl substituents were synthesized . These epoxides together with the commercially available compounds 2-biphenylyl glycidyl ether were examined for dose-mutagenicity relationships using the plate incorporation Ames test with Salmonella typhimurium strains TA100 and TA1535 . Structure-mutagenicity relationships were further examined for these compounds and 3 phenyl glycidyl ethers by concurrent testing at a single dose with strain TA100 . Meaningful correlations could not be established for the mutagenicity of these epoxides to their molecular volumes, partition values, nor to their reactivities with the model nucleophile, 4-(4-nitrobenzyl) pyridine . However, it was noted that increased conjugated aromatic unsaturation with its resulting planarity led to increased mutagenicity and that this effect decreased when it was further removed from the epoxide moiety. J Bacteriol, 1988 Sep, 170(9), 3855 - 63 Ethanolamine utilization in Salmonella typhimurium; Roof DM et al.; Ethanolamine can serve as the sole source of carbon and nitrogen for Salmonella typhimurium if vitamin B12 is present to serve as a cofactor . The pathway for ethanolamine utilization has been investigated in order to understand its regulation and determine whether the pathway is important to the selective forces that have maintained the ability to synthesize B12 in S . typhimurium . We isolated mutants that are defective in ethanolamine utilization (eut mutants) . These mutants defined a cluster of genes located between purC and cysA at 50 min on the Salmonella chromosome . A genetic map of the eut region was constructed . Included in the map are mutations which affect ethanolamine ammonia lyase, the first degradative enzyme, and mutations which affect the second enzyme in the pathway, acetaldehyde dehydrogenase . Transcriptional regulation of the eut genes was studied by using eut-lac operon fusions created by insertion of Mu d lac . Transcription is induced by the simultaneous presence of ethanolamine and B12 in the growth medium . The eut genes constitute a single unit of transcription . One class of mutations located at the promoter-distal end of the eut operon prevent induction of transcription. Infect Immun, 1988 Sep, 56(9), 2407 - 11 Role of H-2 and non-H-2 genes in control of bacterial clearance from the spleen in Salmonella typhimurium-infected mice; Nauciel C et al.; The ability of mice to clear Salmonella typhimurium from their spleens in the late phase of infection was studied after inoculation with a temperature-sensitive mutant . Clearance of bacteria was delayed in C57BL/6 mice compared with BALB/c, C3H/HeJ, DBA/2, A/J, and CBA mice . The responses of F1 hybrids, backcrosses, and recombinant inbred strains derived from C57BL/6 and BALB/c (both Itys) and of H-2 congenic mice were analyzed . The results showed that the low rate of bacterial clearance was recessive, that the rate of clearance was under polygenic control, and that an H-2-linked gene(s) plays a major role . Among H-2 congenic mice with a C57BL/10 background, three phenotypes of bacterial clearance could be distinguished: high (H-2j, H-2q, and H-2u), intermediate (H-2d, H-2f, H-2k, H-2p, H-2r, H-2s, and H-2v), and low (H-2b) rates . The effect of the H-2 complex was apparent with different genetic backgrounds (Itys and Ityr) . In recombinant inbred strains derived from C57BL/6 (Itys) and A/J (Ityr) mice, the effect of the H-2b haplotype on bacterial clearance appeared to be fully expressed only in strains carrying the Itys allele. Infect Immun, 1988 Sep, 56(9), 2209 - 17 Roles of motility, chemotaxis, and penetration through and growth in intestinal mucus in the ability of an avirulent strain of Salmonella typhimurium to colonize the large intestine of streptomycin-treated mice; McCormick BA et al.; Previously, it had been shown that an avirulent strain of Salmonella typhimurium, SL5316, with wild-type lipopolysaccharide (LPS) was a far better colonizer of the streptomycin-treated CD-1 mouse large intestine, was far more motile, did not bind to mouse intestinal mucus nearly as well as, but penetrated through a layer of intestinal mucus in vitro far better than an almost isogenic LPS-deficient transductant, SL5325 . In the present investigation, a nonflagellated transductant, SL5681, and a nonchemotactic transductant, SL5784, were isolated from SL5316 and tested for relative colonizing ability versus SL5316 (smooth) and SL5325 (rough) in streptomycin-treated mice . In addition, the Salmonella strains were tested for their ability to grow together in cecal intestinal mucus and in cecal luminal contents, for their tumbling and swimming activities after growth in cecal mucus, and for their ability to adhere to and travel through cecal mucus in vitro . The data show that the nonflagellated and nonchemotactic derivatives colonized large intestine nearly as well as their parent and were far better colonizers than the LPS-deficient mutant, that all the strains grew equally well in cecal mucus but did not grow in cecal luminal contents, and that cecal mucus-grown strains lost tumbling and swimming activities . Furthermore, the LPS-deficient strain adhered to cecal mucus far better but penetrated mucus far worse than did the nonflagellated transductant, the nonchemotactic transductant, and the parent . Thus, motility and chemotaxis do not appear to play a major role in the ability of the avirulent S . typhimurium strains to colonize the mouse large intestine, colonization may require growth in cecal mucus but does not depend on growth in cecal luminal contents, growth in cecal mucus inhibits S . typhimurium motility, and increased adhesion of the LPS-deficient mutant to cecal mucus and its poor ability to penetrate cecal mucus may play a role in its poor intestine-colonizing ability. Mutat Res, 1988 Sep, 206(1), 83 - 90 Mutagenicity of amino acid and glutathione S-conjugates in the Ames test; Vamvakas S et al.; The mutagenicity of the glutathione S-conjugate S-(1,2-dichlorovinyl)glutathione (DCVG), the cysteine conjugates S-(1,2-dichlorovinyl)-L-cysteine (DCVC) and S-(1,2-dichlorovinyl)-DL-alpha-methylcysteine (DCVMC), and the homocysteine conjugates S-(1,2-dichlorovinyl)-L-homocysteine (DCVHC) and S-(1,2-dichlorovinyl)-DL-alpha-methylhomocysteine (DCVMHC) was investigated in Salmonella typhimurium strain TA2638 with the preincubation assay . DCVC was a strong, direct-acting mutagen; the cysteine conjugate beta-lyase inhibitor aminooxyacetic acid decreased significantly the number of revertants induced by DCVC; rat renal mitochondria (11,000 X g pellet) and cytosol (105,000 X g supernatant) with high beta-lyase activity increased DCVC mutagenicity at high DCVC concentrations . DCVG was also mutagenic without the addition of mammalian activating enzymes; the presence of low gamma-glutamyltransferase activity in bacteria, the reduction of DCVG mutagenicity by aminooxyacetic acid, and the potentiation of DCVG mutagenicity by rat kidney mitochondria and microsomes (105,000 X g pellet) with high gamma-glutamyltransferase activity indicate that gamma-glutamyltransferase and beta-lyase participate in the metabolism of DCVG to mutagenic intermediates . The homocysteine conjugate DCVHC was only weakly mutagenic in the presence of rat renal cytosol, which exhibits considerable gamma-lyase activity, this mutagenic effect was also inhibited by aminooxyacetic acid . The conjugates DCVMC and DCVMHC, which are not metabolized to reactive intermediates, were not mutagenic at concentrations up to 1 mumole/plate . The results demonstrate that gamma-glutamyltransferase and beta-lyase are the key enzymes in the biotransformation of cysteine and glutathione conjugates to reactive intermediates that interact with DNA and thereby cause mutagenicity. Mol Gen Genet, 1988 Sep, 214(1), 11 - 5 Operon structure of flagellar genes in Salmonella typhimurium; Kutsukake K et al.; In Salmonella typhimurium, more than 40 genes have been shown to be involved in flagellar formation and function and almost all of them have been assigned to three regions of the chromosome, termed region I, region II, and region III . In the present study, a large number of transposon-insertion mutants in these flagellar genes were isolated using Tn10 and Mud1 . The flaV gene was found to be a strong hot spot for Tn10 insertion . Complementation analysis of the polarity effects exerted by the transposon-insertion mutants defined 13 different flagellar operons; 3 in region I, 4 in region II, and 6 in region III . These results are compared with the reported arrangement of the corresponding genes in Escherichia coli. Mutat Res, 1988 Sep, 201(1), 169 - 80 Mechanisms of mutagenicity and toxicity of sodium selenite (Na2SeO3) in Salmonella typhimurium; Kramer GF et al.; The mechanisms of selenite toxicity and mutagenicity in S . typhimurium have been characterized . In contrast to previous reports, selenite toxicity was shown not to involve nonspecific incorporation into protein via the sulfur metabolic pathways . Selenite toxicity was, however, shown to involve its ability to act as an oxidizing agent, primarily through reactions with sulfhydryls . Strains which lack glutathione (GSH) are more sensitive to killing by sulfhydryl reagents . The selenite sensitivity of such a mutant was a biphasic phenomenon . The mutant was much more sensitive than a strain which contained GSH at lower selenite concentrations whereas, at higher concentrations, the mutant was much more resistant to selenite . The mechanism of selenite toxicity at lower concentrations in this mutant thus appeared to involve damage to intracellular sulfhydryls . The sensitization to higher doses of selenite by GSH could be explained by the generation of toxic oxygen species . The in vitro reactions of selenite with both cysteine and GSH readily produced H2O2 and O2- . A S . typhimurium strain which overproduces superoxide dismutase (SOD) and catalase was more resistant to high concentrations of selenite, but not killing by the lower doses . Pretreatment of cells with a nonlethal dose of selenite induced the synthesis of proteins which protected the cells from killing by H2O2 or high doses of selenite . Selenite was also a mutagen in the tester strain TA104, in which a number of other oxidizing agents have also been found to be mutagens . These results were consistent with a model in which the reactions of selenite and intracellular thiols with concomitant production of active oxygen species are the primary causal agents of selenite mutagenicity and toxicity in S . typhimurium. Mutat Res, 1988 Sep, 194(2), 131 - 41 A mutation in the DNA adenine methylase gene (dam) of Salmonella typhimurium decreases susceptibility to 9-aminoacridine-induced frameshift mutagenesis; Ritchie L et al.; A mutant of Salmonella typhimurium with a reduced response to mutation induction by 9-aminoacridine (9AA) has been isolated . The mutation (dam-2) is located in the DNA adenine methylase gene . The dam-2 mutant strain exhibits a level of sensitivity to 2-aminopurine (2AP) intermediate between that of the dam+ and the DNA adenine methylation-deficit dam-1 strain, and 2AP sensitivity was reversed by introduction of a mutH mutation or of the plasmid pMQ148 (which carries a functional Escherichia coli dam+ gene) . However, the dam-2 strain is not grossly defective in DNA adenine methylase activity . Whole cell DNA appears full methylated at -GATC- sites . The levels of 9AA required to induce equivalent levels of frameshift mutagenesis in the dam-2 strain were approximately 2-fold higher than for the dam+ strain . Introduction of pMQ148 dam+ reduced the level of 9AA required for induction of frameshift mutations 4-fold in the dam-2 strain and 2-fold in the dam+ strain . The dam-2 mutation had no effect on the levels of ICR191 required for induction of frameshift mutations, but introduction of pMQ148 reduced the ICR191-induced mutagenesis 2-fold . The dam+/pMQ148, dam-2/pMQ148 and dam-1/pMQ148 strains showed identical dose-response curves for both 9AA and ICR191 . These results are consistent with a slightly reduced (dam-2) or increased (pMQ148) rate of methylation at the replication fork . The 2AP sensitivity of the dam-2 strain cannot be simply explained . Furthermore, addition of methionine to the assay medium reverses the 2AP sensitivity of the dam-2 strain, but has no effect on 9AA mutagenesis. J Bacteriol, 1988 Sep, 170(9), 4304 - 8 Genetic evidence for modulation of the activator by two regulatory proteins involved in the exogenous induction of phosphoglycerate transport in Salmonella typhimurium; Jiang SQ et al.; Previous work from this laboratory has identified in a fragment of DNA, cloned from Salmonella typhimurium, two genes involved in the exogenous induction of phosphoglycerate transport . These two genes, the transporter gene, pgtP, and the activator gene, pgtA, are closely linked physically; they are only 3.4 kilobases apart . In the accompanying paper, we describe the determination of the nucleotide sequence of this 3.4-kilobase DNA segment and show that this segment contains two genes, pgtB and pgtC, encoding two polypeptides of 593 and 397 amino acid residues, respectively . This paper presents an analysis of the effects of insertions and deletions in pgtBC on the expression of pgtP gene and on the expression of lacZ fused to the pgtP gene . The results indicate that both pgtBC genes are necessary for expression of the pgtP gene . Strikingly, deletion of both genes resulted in a constitutive phenotype, suggesting that PgtB and PgtC polypeptides modulate PgtA activity . The expression of the pgtP gene appears to be regulated by the pgtA gene product, which acts as an activator . A model of induction is proposed in which the central feature is the interaction of the three regulatory proteins in the membrane such that the activity of the activator (PgtA) is subject to modulation by the binding of an inducer. J Bacteriol, 1988 Sep, 170(9), 4299 - 303 Identification of the products and nucleotide sequences of two regulatory genes involved in the exogenous induction of phosphoglycerate transport in Salmonella typhimurium; Yang YL et al.; We describe the determination of the nucleotide sequence of two genes (pgtB and pgtC) contained within the 3.4-kilobase DNA segment sandwiched between the transporter gene, pgtP, and the regulatory gene, pgtA . These two genes are involved in the regulation of expression of phosphoglycerate transport in Salmonella typhimurium . The sequence indicates the presence of two large open reading frames, potentially coding for two polypeptides of 397 and 593 amino acid residues . The two gene products were identified by using the bacteriophage T7 RNA polymerase-T7 promoter coupled system of Tabor and Richardson, and the observed apparent mass of 45 and 69 kilodaltons correlated well with the respective open reading frames . The cellular location of these two polypeptides was directly determined, and the polypeptides were found to be associated with the membrane . Although overall these polypeptides appear to be hydrophilic, there is one hydrophobic transmembrane segment in the smaller polypeptide and four such segments in the larger polypeptide which can account for their association with the membrane . In the accompanying paper, we present genetic evidence that pgtB and pgtC genes are involved in the induction of the pgtP expression by modulating derepressor activity. J Bacteriol, 1988 Sep, 170(9), 4119 - 24 Organization and temporal expression of a flagellar basal body gene in Caulobacter crescentus; Hahnenberger KM et al.; Caulobacter crescentus assembles a single polar flagellum at a defined time in the cell cycle . The protein components of the flagellar hook and filament are synthesized just prior to their assembly . We demonstrated that the expression of a gene, flaD, that is involved in the formation of the flagellar basal body is under temporal control and is transcribed relatively early in the cell cycle, before the hook and flagellin genes are transcribed . Thus, the order of flagellar gene transcription reflects the order of assembly of the protein components . A mutation in the flaD gene results in the assembly of a partial basal body which is missing the outermost P and L rings as well as the external hook and filament (K.M . Hahnenberger and L . Shapiro, J . Mol . Biol . 194:91-103, 1987) . The flaD gene was cloned and characterized by nucleotide sequencing and S1 nuclease protection assays . In contrast to the protein components of the hook and filament, the protein encoded by the flaD gene contains a hydrophobic leader peptide . The predicted amino acid sequence of the leader peptide of flaD is very similar to the leader peptide of the flagellar basal body P ring of Salmonella typhimurium (M . Homma, Y . Komeda, T . Iino, and R.M . Macnab, J . Bacteriol . 169:1493-1498, 1987). J Bacteriol, 1988 Sep, 170(9), 3991 - 5 Construction of delta aroA his delta pur strains of Salmonella typhi; Edwards MF et al.; Salmonella typhi strains with two deletion mutations, each causing an attenuating auxotrophy, have been constructed from strains Ty2 and CDC 10-80 for possible use as oral-route live vaccines . An aroA(serC)::Tn10 transposon insertion was first transduced from a Salmonella typhimurium donor into each wild-type S . typhi strain . Transductants of the Aro- SerC- phenotype were treated with transducing phage grown on an S . typhimurium strain with an extensive deletion at aroA; selection for SerC+ yielded transductants, some of which were delta aroA . A his mutation was next inserted into a delta aroA strain in each line by two steps of transduction . Two deletions affecting de novo purine biosynthesis were used as second attenuating mutations: delta purHD343, causing a requirement for hypoxanthine (or any other purine) and thiamine, and delta purA155, causing an adenine requirement . The purHD343 deletion was introduced into the delta aroA his derivatives of each strain by cotransduction with purH::Tn10, and the purA155 deletion was introduced into the CDC 10-80 delta aroA his derivative by cotransduction with an adjacent silent Tn10 insertion by selection for tetracycline resistance . Tetracycline-sensitive mutants of each of the three delta aroA his delta pur strains were isolated by selection for resistance to fusaric acid . The tetracycline-sensitive derivative of the CDC 10-80 delta aroA his delta purA155 strain, designated 541Ty, and its Vi-negative mutant, 543Ty, constitute the candidate oral-route live-vaccine strains used in a recent volunteer trail (M . M . Levine, D . Herrington, J . R . Murphy, J . G . Morris, G . Losonsky, B . Tall, A . A . Lindberg, S . Stevenson, S . Baqar, M . F . Edwards, and B . A . D . Stocker, J . Clin . Invest . 79:885-902, 1987) . Tetracycline-sensitive mutants of the delta aroA his delta purHD derivative of strains Ty2 and CDC 10-80 may also be appropriate as live vaccines but have not been tested as such. J Bacteriol, 1988 Sep, 170(9), 3903 - 9 Differential regulation by cyclic AMP of starvation protein synthesis in Escherichia coli; Schultz JE et al.; Of the 30 carbon starvation proteins whose induction has been previously shown to be important for starvation survival of Escherichia coli, two-thirds were not induced in cya or crp deletion mutants of E . coli at the onset of carbon starvation . The rest were induced, although not necessarily with the same temporal pattern as exhibited in the wild type . The starvation proteins that were homologous to previously identified heat shock proteins belonged to the latter class and were hyperinduced in delta cya or delta crp mutants during starvation . Most of the cyclic AMP-dependent proteins were synthesized in the delta cya mutant if exogenous cyclic AMP was added at the onset of starvation . Furthermore, beta-galactosidase induction of several carbon starvation response gene fusions occurred only in a cya+ genetic background . Thus, two-thirds of the carbon starvation proteins of E . coli require cyclic AMP and its receptor protein for induction; the rest do not . The former class evidently has no role in starvation survival, since delta cya or delta crp mutants of either E . coli or Salmonella typhimurium survived starvation as well as their wild-type parents did . The latter class, therefore, is likely to have a direct role in starvation survival . This possibility is strengthened by the finding that nearly all of the cya- and crp-independent proteins were also induced during nitrogen starvation and, as shown previously, during phosphate starvation . Proteins whose synthesis is independent of cya- and crp control are referred to as Pex (postexponential). Carcinogenesis, 1988 Sep, 9(9), 1523 - 7 Fusarium moniliforme metabolites: genotoxicity of culture extracts; Lu SJ et al.; Fusarin C (FC) is a potent mutagen which has been isolated from Fusarium moniliforme culture extracts (FME) . We have confirmed that the mutagenicity of these extracts is enhanced by phenobarbital- or Aroclor-induced microsomes and shown that: (i) additional, direct-acting, mutagens are present in crude extracts from F . moniliforme cultures; (ii) Salmonella typhimurium TA 100 exposed to FME in the presence of S9 mixtures shows an increased number of DNA strand breaks as detected by intercalation of ethidium bromide; (iii) exposure of polyoma-transformed rat fibroblast cells to HPLC-purified FC induced asynchronous replication of polyoma DNA sequences, a phenomenon also observed when these cells were exposed to a variety of other carcinogens; (iv) FME can alkylate 4-(p-nitrobenzyl)pyridine in the absence of S9 mix, although less efficiently than styrene oxide; and (v) these additional direct-acting mutagens, present in crude extracts from F . moniliforme cultures, may be responsible for the DNA adducts formed by reaction with calf thymus DNA in the absence of metabolic activation and detected by the 32P-postlabeling assay . All of these observations suggest that significant health effects may be associated with human exposure to F . moniliforme and that further studies on its metabolites are needed. J Mol Biol, 1988 Aug 20, 202(4), 787 - 808 Three-dimensional reconstruction of the flagellar filament of Caulobacter crescentus . A flagellin lacking the outer domain and its amino acid sequence lacking an internal segment; Trachtenberg S et al.; We obtained a three-dimensional reconstruction of the flagellar filament of Caulobacter crescentus CB15 from electron micrographs of negatively stained preparations . The C . crescentus filament appears, both in negative stain and in the frozen-hydrated state, significantly smoother and narrower than other filaments . Its helical symmetry, and unit cell size, however, are similar to that of other filaments . Although the molecular weight of the C . crescentus flagellin is about half that of other plain flagellins, there is only one monomer per unit cell as indicated by diffraction studies and by linear mass density measurements with the scanning transmission electron microscope . Alignment of the primary amino acid sequences of Salmonella typhimurium (serotype i) and C . crescentus (29,000 Mr) flagellins shows that whereas there is homology at the amino and carboxyterminal ends of the two sequences, the central segment of the S . typhimurium sequence has no homology to that of C . crescentus . A correlated comparison between the three-dimensional reconstructions of the two filaments and primary amino acid sequences of the two flagellins suggests that: (1) the C . crescentus subunit is missing the outer molecular domain but is, otherwise, similar to that of S . typhimurium; (2) the outer molecular domain in S . typhimurium corresponds, therefore, to a central stretch of the primary amino acid sequence; and (3) the outer molecular domain, missing in C . crescentus, is not obligatory for flagellar motility. Carcinogenesis, 1988 Aug, 9(8), 1513 - 5 Modifying role of vitamins on the mutagenic action of N-methyl-N'-nitro-N-nitrosoguanidine; Shetty TK et al.; Several vitamin compounds have been tested for their ability to suppress the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine, a direct acting mutagen/carcinogen, in Salmonella typhimurium strain TA100 . Menadione, alpha-tocopherol, retinal and retinol have displayed high inhibitory activity . The antimutagenic activity of menadione, in particular, has been found to be remarkable in as much as less than equimolar amount can reduce the mutagenic potency of the carcinogen by 50% . In vitro data suggest that its action is mediated by accelerating the deactivation of the N-nitroso carcinogen, possibly involving the formation of a quinone radical. J Appl Toxicol, 1988 Aug, 8(4), 243 - 8 In vitro mutagenicity of water contaminants in complex mixtures; Varma MM et al.; Trihalomethanes, Carbon tetrachloride and trichloroethylene were tested in single, binary and multi-complex mixtures using standard tester strains TA1535, TA1537, TA98 and TA100 of Salmonella typhimurium with and without addition of an in vitro metabolizing fraction S-9 . Chloroform (CHCl3) was found to be mutagenic in all strains without S-9 activation . However, when tested with Bromoform (15%), which was nonmutagenic singly, the combined effect of the mixture was nonmutagenic . CCl4 was a direct mutagen (without S-9) in all strains except TA 1535 . When combined with 85% CHCl3, only strains TA1535 and TA1537 were mutagenic . When tested with mammalian activation (S-9), CCl4 was mutagenic in all strains . However, when tested with CHCl3 (CHCl3 and CCl4-85:15), the mutagenic capability was lost . With or without S-9 Activation multi-complex mixture of CHCl3, CCl4 and TCE (85:8:7) was mutagenic for a narrow range of doses in all strains. J Med Microbiol, 1988 Aug, 26(4), 281 - 4 Changes in hepatic superoxide dismutase and xanthine oxidase activity in mice infected with Salmonella typhimurium and Pseudomonas aeruginosa; Takahashi M et al.; Liver xanthine oxidase (XOD) and superoxide dismutase (SOD) activities were compared in mice during Salmonella typhimurium and Pseudomonas aeruginosa infections . We observed that XOD activity rose but SOD activity fell for the first 11 days after infection with smooth type S . typhimurium, coinciding with the period of bacterial growth in the liver . Rough type S . typhimurium did not establish an infection and mice inoculated with this strain showed no variation in enzyme activities . P . aeruginosa infection was mild but stimulated both XOD and SOD activities. Jpn J Genet, 1988 Aug, 63(4), 343 - 57 Cloning and nucleotide sequence of the brnQ gene, the structural gene for a membrane-associated component of the LIV-II transport system for branched-chain amino acids in Salmonella typhimurium; Ohnishi K et al.; The genetically defined gleR-brnQ region responsible for the branched-chain amino acid transport in Salmonella typhimurium was mapped in the 3.3-kilobase SalI-PstI segment of plasmid pOH56 by complementation analysis . By subcloning and genetic recombination analysis, the gleR and brnQ3 mutational sites were localized within the 0.85-kilobase SalI-EcoRV segment, and brnQ4 within the 0.8-kilobase EcoRV-HindIII segment . The nucleotide sequence of the brnQ gene and its flanking regions was determined . The brnQ gene is encoded by the sequence starting 24 base pairs upstream from the EcoRV site . Transcription of the brnQ gene starts at three sites separated by 171, 173 and 174 nucleotides, respectively, from the initiation codon . The promoter sequences can be seen in the immediate upstream region of the transcription initiation sites . There is a long silent region between the transcription initiation sites and a potential Shine-Dalgarno nucleotide sequence . The coding sequence of the brnQ gene, which is 1317 base pairs long, specifies a very hydrophobic protein of 439 amino acid residues. Food Chem Toxicol, 1988 Aug, 26(8), 691 - 8 Impaired murine resistance to Salmonella typhimurium following oral exposure to the trichothecene T-2 toxin; Tai JH et al.; On orally exposing Salmonella-resistant C3H/HeN mice to the trichothecene T-2 toxin (1 mg/kg body weight), challenging with Salmonella typhimurium, and continuing to dose with T-2 toxin on alternate days for 3 wk, the LD50 for the organism decreased by five orders of magnitude, in comparison with control mice not treated with T-2 toxin . In the absence of S . typhimurium, T-2 toxin did not cause lethal effects when administered at this level . Increased mortality in response to S . typhimurium challenge was dependent on T-2 toxin dose in the range 0 to 1 mg/kg for this regimen . The toxin did not significantly affect intestinal infection but did increase splenic counts in mice challenged with a range of S . typhimurium doses and also accelerated body-weight loss in infected animals . Mice challenged with the organism exhibited similar mortality when T-2 toxin treatment was begun 1 day prior to infection or at 5 or 9 days after infection . A time-related decrease in mortality, relative to that found for the standardized co-challenge described above, was observed when T-2 toxin administration was begun at 9, 13 or 23 days after infection . The results indicated that, depending on the challenge dose of the organism, both early and late phase acquired immune response to S . typhimurium could be impaired by T-2 toxin . Markedly enhanced susceptibility to gram-negative bacterial infection is another manifestation of trichothecene toxicity and may be an important aetiological factor in animal health problems that are associated with these mycotoxins. Toxicol Lett, 1988 Aug, 42(2), 193 - 8 Effect of certain trace elements on the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine; Francis AR et al.; Tests have been carried out to detect inhibitory activity of various trace elements on mutagenesis induced by the carcinogen N-methyl-N'-nitro-N-nitrosoguanidine in Salmonella typhimurium strain TA100 . Selenium has been found to be most active in this regard while copper has displayed moderate inhibitory ability . The action of selenium is mediated through an interaction resulting in rapid deactivation of the carcinogen. J Bacteriol, 1988 Aug, 170(8), 3627 - 32 Pausing of flagellar rotation is a component of bacterial motility and chemotaxis; Lapidus IR et al.; When bacterial cells are tethered to glass by their flagella, many of them spin . On the basis of experiments with tethered cells it has generally been thought that the motor which drives the flagellum is a two-state device, existing in either a counterclockwise or a clockwise state . Here we show that a third state of the motor is that of pausing, the duration and frequency of which are affected by chemotactic stimuli . We have recorded on video tape the rotation of tethered Escherichia coli and Salmonella typhimurium cells and analyzed the recordings frame by frame and in slow motion . Most wild-type cells paused intermittently . The addition of repellents caused an increase in the frequency and duration of the pauses . The addition of attractants sharply reduced the number of pauses . A chemotaxis mutant which lacks a large part of the chemotaxis machinery owing to a deletion of the genes from cheA to cheZ did not pause at all and did not respond to repellents by pausing . A tumbly mutant of S . typhimurium responded to repellents by smooth swimming and to attractants by tumbling . When tethered, these cells exhibited a normal rotational response but an inverse pausing response to chemotactic stimuli: the frequency of pauses decreased in response to repellents and increased in response to attractants . It is suggested that (i) pausing is an integral part of bacterial motility and chemotaxis, (ii) pausing is independent of the direction of flagellar rotation, and (iii) pausing may be one of the causes of tumbling. J Bacteriol, 1988 Aug, 170(8), 3509 - 12 Mode of peptidoglycan synthesis in Salmonella typhimurium: single-strand insertion; Cooper S et al.; The synthesis of peptidoglycan by Salmonella typhimurium at the molecular level has been analyzed by studying the pattern of insertion of newly synthesized strands into the preexisting cell wall . We have measured the acceptor-donor radioactivity ratio during short labeling periods, and we found values between 0 and 0.2 . This is less than the ratio observed by Burman and Park (Proc . Natl . Acad . Sci . USA, 81:1844-1848) for peptidoglycan synthesis in Escherichia coli . We propose that insertion of new strands occurs as single strands. J Bacteriol, 1988 Aug, 170(8), 3421 - 6 Nucleotide sequence and transcription start point of the phosphoglycerate transporter gene of Salmonella typhimurium; Goldrick D et al.; We identified the phosphoglycerate transporter gene of Salmonella typhimurium and its polypeptide product and determined the nucleotide sequence of the gene . The predicted translation product was a protein of 406 amino acid residues and was extremely hydrophobic, a feature that is consistent with its role in membrane transport . Hydropathy analysis suggested that there are eight transmembrane segments of at least 20 amino acid residues for the protein . The transcription start point was mapped to lie at position -44 relative to the putative translational initiation start point . Comparison of PgtP with UhpT and GlpT, the membrane-bound proteins involved in the transport of hexose-6-phosphate and glycerol-3-phosphate, respectively, revealed a very high degree of amino acid sequence similarity among them, reflecting not only similar structures and functions among these polypeptides but also a common evolutionary origin for them. Epidemiol Infect, 1988 Aug, 101(1), 75 - 82 Salmonella typhimurium phage type 141 infections in Sheffield during 1984 and 1985: association with hens' eggs; Chapman PA et al.; Food poisoning due to Salmonella typhimurium phage type 141 was unusual in the Sheffield area before 1984 . The sudden increase in incidence of this phage type during 1984 and 1985, and its causative role in several small outbreaks in this period have been investigated . Epidemiological and laboratory investigations suggested that hens' eggs were the most likely source of S . typhimurium phage type 141. EMBO J, 1988 Aug, 7(8), 2611 - 7 Overproduction of peroxide-scavenging enzymes in Escherichia coli suppresses spontaneous mutagenesis and sensitivity to redox-cycling agents in oxyR-mutants; Greenberg JT et al.; Mutations that suppressed the H2O2 sensitivity of Escherichia coli oxyR- strains caused elevated levels of one three enzymes that destroy organic and hydrogen peroxides: catalase-hydroperoxidase I (the katG gene product), catalase-hydroperoxidase II (controlled by katEF) or alkyl hydroperoxide reductase (specified by the ahp genes) . The continuous high-level expression of any one of these enzymes also conferred resistance in an oxyR deletion mutant against other compounds such as N-ethylmaleimide and the superoxide-generator menadione . Overproduction of alkyl hydroperoxide reductase, but not of the catalases, gave resistance to the organic oxidant cumene hydroperoxide . The E . coli delta oxyR strains also exhibited a strongly elevated frequency of spontaneous mutagenesis, as reported for such mutants in Salmonella typhimurium . This mutagenesis was greatly diminished by the individual overexpression of these scavenging enzymes . All of these phenotypes--enzyme overproduction, resistance to oxidants and suppression of spontaneous mutagenesis--remained linked upon transduction of the mutant katG or ahp genes . Peroxides thus appear to mediate the toxicity of a variety of redox agents, and are produced in sufficient quantity during normal metabolism to cause a substantial increase in 'spontaneous' mutations in cells that lack adequate antioxidant defenses. Mol Gen Genet, 1988 Aug, 213(2-3), 332 - 8 Characterization of Tn10d-Cam: a transposition-defective Tn10 specifying chloramphenicol resistance; Elliott T et al.; We have constructed a small, transposition-defective derivative of the transposon Tn10 that carries the chloramphenicol acetyltransferase gene of pACYC184 . This new genetic element, Tn10d-Cam, transposes when Tn10 transposase is provided from a multi-copy plasmid . Transposon insertion mutagenesis of Salmonella typhimurium was performed by using a strain carrying a Tn10d-Cam insertion in an Escherichia coli F' episome as the donor in transductional crosses into recipients that carried a plasmid expressing Tn10 transposase . Tn10d-Cam insertion mutations were also generated by complementation in cis of Tn10d-Cam by a cotransducible Tn10 element that overproduces transposase . Here, transposase was provided only transiently, and the Tn10d-Cam insertion mutations were recovered in a transposase-free strain . Cis complementation was used for mutagenesis of a plasmid target . The site specificity of insertion and the effect of insertions on expression of a downstream gene were investigated, using Tn10d-Cam insertions in a plasmid carrying a segment of the histidine operon. J Bacteriol, 1988 Aug, 170(8), 3725 - 30 Salmonella typhimurium mutants lacking NAD pyrophosphatase; Park UE et al.; NAD can serve as both a purine and a pyridine source for Salmonella typhimurium . Exogenous NAD is rapidly broken down into nicotinamide mononucleotide and AMP by an NAD pyrophosphatase, the first step in the pathway for the assimilation of exogenous NAD . We isolated and characterized mutants of S . typhimurium lacking NAD pyrophosphatase activity; such mutants were identified by their failure to use exogenous NAD as a purine source . These mutants carry mutations that map at a new locus, designated pnuE, between 86 and 87 min on the Salmonella chromosome. J Bacteriol, 1988 Aug, 170(8), 3682 - 8 Dominant lethal mutations in the dnaB helicase gene of Salmonella typhimurium; Maurer R et al.; A class of dominant lethal mutations in the dnaB (replicative helicase) gene of Salmonella typhimurium is described . The mutated genes, when present on multicopy plasmids, interfered with colony formation by Escherichia coli host strains with a functional chromosomal dnaB gene . The lethal phenotype was expressed specifically in supE (glutamine-inserting) host strains and not in Sup+ strains, because the mutant genes, by design, also possessed an amber mutation derived from a glutamine codon . Mutations located at 11 sites by deletion mapping and DNA sequence analysis varied in the temperature dependence and severity of their lethal effects . None of the mutations complemented a dnaB(Ts) host strain at high temperature (42 degrees C) . Therefore, these nonfunctional DnaB proteins must engage some component(s) of the DNA replication machinery and inhibit replication . These mutations are predicted to confer limited, specific defects in either the catalytic activity of DnaB or the ability of DnaB to interact with one of its ligands such as DNA, nucleotide, or another replication protein . The variety of mutant sites and detailed phenotypes represented in this group of mutations may indicate the operation of more than one specific mechanism of lethality. Proc Natl Acad Sci U S A, 1988 Aug, 85(15), 5620 - 4 Chromosomal location and structure of the operon encoding peptide-chain-release factor 2 of Escherichia coli; Kawakami K et al.; The prfB gene encodes peptide-chain-release factor 2 of Escherichia coli, which catalyzes translation termination at UGA and UAA codons . The gene, identified by sequencing, is located at the 62-min region of the E . coli chromosome . The prfB gene is followed by an open reading frame encoding a 57,603-Da protein . This downstream open reading frame was identified as herC, a gene defined by a suppressor mutation that restores replication of a ColE1 plasmid mutant . RNA blot hybridization and S1 nuclease protection analyses of in vivo transcripts showed that prfB and herC are cotranscribed into a 2800-base transcript in the counterclockwise direction with respect to the E . coli genetic map . Thus, we refer to the two genes as the prfB-herC operon . Data are presented that suggest that supK, a mutation in Salmonella typhimurium that suppresses UGA termination, is the structural gene for Salmonella release factor 2 . Translation control within the prfB-herC operon and the relationship of these genes to a tRNA methyltransferase are discussed. Nucleic Acids Res, 1988 Jul 25, 16(14B), 6789 - 802 IS150: distribution, nucleotide sequence and phylogenetic relationships of a new E . coli insertion element; Schwartz E et al.; Recently we identified the new insertion (IS) sequence IS150 in various strains of Escherichia coli K-12 . We have screened other strains of E . coli and Salmonella typhimurium for the presence of homologous sequences . The strains of E . coli K-12 and W tested contain one or more copies of homology to IS150 . We have also determined the complete nucleotide sequence of a copy of IS150 inserted into IS1 . Comparison of nucleotide and deduced amino acid sequences of IS150, IS2, IS3, IS51, IS600 and IS629 reveals significant homologies suggesting that these elements are members of a family of phylogenetically related insertion sequences. Med J Aust, 1988 Jul 18, 149(2), 94 - 5 Mycotic aneurysm of the thoracic aorta caused by Salmonella typhimurium; Golledge CL et al.; A fatal case of mycotic aneurysm of the thoracic aorta is described . Salmonella typhimurium was isolated from blood cultures and from cultures of a post-mortem sample of the aneurysm . A review of the literature showed that while endovascular infection is a recognized complication of salmonellal septicaemia in the elderly, infection of the thoracic aorta by Salmonella spp . is rare . A combination of surgery and antibiotic therapy always is required for a successful outcome. J Biol Chem, 1988 Jul 5, 263(19), 9155 - 61 The yeast SEC53 gene encodes phosphomannomutase; Kepes F et al.; Yeast sec53 cells incubated at a restrictive temperature (37 degrees C) accumulate inactive and incompletely glycosylated forms of secretory proteins within the lumen of the endoplasmic reticulum . A defect in glycosylation of alpha-factor precursor has been reproduced in vitro using membranes and cytosol isolated from sec53 mutant cells . Normal glycosylation is restored in reactions supplemented with a cytosolic fraction from wild type cells, with GDP-mannose, or with mannose 1-phosphate and GTP, but not with mannose 6-phosphate and GTP . This pattern of stimulation suggests that extracts of sec53 cells are deficient in phosphomannomutase activity or in the production of a precursor of mannose 1-phosphate . Several lines of evidence demonstrate that SEC53 encodes the yeast phosphomannomutase . Direct assay of soluble fractions from independent alleles of sec53 shows low to negligible phosphomannomutase, but nearly normal levels of phosphomannoisomerase activity . The residual phosphomannomutase activity in mutant cell lysates is thermolabile in proportion to the severity of the sec53 cell growth defect . Introduction of the SEC53 gene on a multicopy plasmid into sec53 or wild type yeast and into Salmonella typhimurium results in an increase in phosphomannomutase activity that correlates with elevated expression of the Sec53 protein . Finally, the Sec53 protein and phosphomannomutase activity cofractionate exactly in a 70-fold partial purification involving gel filtration and DEAE chromatography . The secretory defect in sec53 cells may now be explained by a deficit in GDP-mannose production. FEBS Lett, 1988 Jul 4, 234(1), 165 - 8 Inaccurate protein synthesis in a mutant of Salmonella typhimurium defective in transfer RNA pseudouridylation; Negre D et al.; Protein synthesis was studied comparatively in a wild-type strain of Salmonella typhimurium and in hisT mutant cells defective in the pseudouridylation of transfer RNA . From a quantitative point of view, no significant differences between the two types of strain was observed when measuring the rate of protein synthesis during either exponential growth or starvation for histidine . In contrast, the qualitative analysis of proteins by two-dimensional gel electrophoresis showed that histidine-starved hisT cells mistranslate the genetic program at a higher frequency than exponentially growing hisT cells or either starved or unstarved hisT+ cells. J Dairy Sci, 1988 Jul, 71(7), 1756 - 63 Separation of immunoglobulin and transferrin from blood serum and plasma by metal chelate interaction chromatography; Al-Mashikhi SA et al.; Metal chelate interaction chromatography was used to separate Ig, transferrin, and albumin from blood serum and blood plasma . A column was packed with iminodiacetic acid: 1,4-butanediol diglycidyl Sepharose 6B or Sephacryl S-300 and loaded with copper, zinc, nickel, or cobalt ion . Radial immunodiffusion assay indicated that Ig-rich fractions of blood serum obtained from Zn-, Ni-, Co-, and Cu-loaded columns contained 23.2, 81.3, 79.4, and 98.1% active IgG, respectively . Transferrin was recovered from the second peak . When the same conditions of metal chelate interaction chromatography were used for blood plasma, hemoglobin tended to bind strongly to the Cu-loaded column and was eluted only with 50% ethanol . Modification of histidine residues in Ig and transferrin with diethyl pyrocarbonate almost completely destroyed their binding ability to the column . Immunoglobulin G separated showed antilipopolysaccharide antibody activity against Escherichia coli, Salmonella typhimurium, and Bordettella parapertussis. Carcinogenesis, 1988 Jul, 9(7), 1277 - 81 Metabolism and mutagenic activity of benzo{k}fluoranthene and 3-, 8- and 9-fluorobenzo{k}fluoranthene; Weyand EH et al.; The metabolism of 3-, 8- and 9-fluorobenzo{k}fluoranthene (B{k}F) relative to B{k}F was investigated . The major metabolites of B{k}F formed in vitro using rat liver S-9 metabolism systems were 8,9-dihydro-8,9-dihydroxyB{k}F, the 2,3-quinone of B{k}F and 3-, 8- and 9-hydroxyB{k}F . Fluorine substitution within the structure of B{k}F substantially altered the types of metabolites formed in vitro . The most pronounced effect was observed with 9-fluoroB{k}F . In contrast to B{k}F, the 8,9-dihydro-8,9-dihydroxy-, 9-hydroxy- and 10,11-dihydro-10,11-dihydroxy derivatives were not detected as metabolites of 9-fluoroB{k}F . However, either the 2,3- or 4,5-dihydrodiol of 9-fluoroB{k}F was detected . In the case of 8-fluoroB{k}F, neither the 8- nor 11-hydroxy- derivatives were detected . The principle dihydrodiols formed from 8-fluoroB{k}F were the 10,11-dihydrodiol and either the 2,3-or 4,5-dihydrodiol . The pattern of metabolites formed with 3-fluoroB{k}F was similar to that observed with B{k}F with the exception that neither the 3- nor 4-hydroxy derivatives were formed . Mass spectral data indicated that fluoro substitution is not lost to any appreciable extent during the metabolism of 3-, 8- and 9-fluoroB{k}F . The mutagenic activity of these B{k}F fluoro derivatives along with B{k}F, 2,3-dihydro-2,3-dihydroxyB{k}F, the 2,3-quinone of B{k}F and 8,9-dihydro-8,9-dihydroxyB{k}F were evaluated in Salmonella typhimurium TA100 in the presence of rat liver S-9 metabolism systems . 3-FluoroB{k}F was more mutagenic than B{k}F, while both 8- and 9-fluoroB{k}F were less active . While the 2,3-dihydrodiol and 2,3-quinone were weakly active, the 8,9-dihydrodiol had similar mutagenic potency to B{k}F. J Exp Med, 1988 Jul 1, 168(1), 25 - 32 Protective immunity evoked by oral administration of attenuated aroA Salmonella typhimurium expressing cloned streptococcal M protein; Poirier TP et al.; Attenuated strains of Salmonella have been used effectively as vaccines against typhoid fever . We have investigated the use of such strains to deliver cloned antiphagocytic virulence determinants of unrelated bacteria . The aroA strain of S . typhimurium SL3261 was transformed with a low-copy plasmid vector pMK207, which contains the cloned gene spm5 encoding streptococcal M protein, the major virulence factor of these organisms . The transformed SL3261 expressed type 5 M protein in the cytoplasmic fraction, and when fed orally to BALB/c mice, evoked both serum and salivary IgA, IgG, and IgM antibodies directed against type 5 M protein . The orally immunized mice were completely protected against both intranasal and intraperitoneal challenge infections with virulent S . typhimurium SL1344 or M5 streptococci . These studies provide evidence that an attenuated strain of Salmonella can be used effectively as a general vaccine vehicle to deliver antiphagocytic virulence determinants of unrelated bacteria. J Bacteriol, 1988 Jul, 170(7), 3150 - 7 DNA sequences of the cysK regions of Salmonella typhimurium and Escherichia coli and linkage of the cysK regions to ptsH; Byrne CR et al.; Nucleotide sequences of the cysK regions of Salmonella typhimurium and Escherichia coli have been determined . A total of 3,812 and 2,595 nucleotides were sequenced from S . typhimurium and E . coli, respectively . Open reading frames of 323 codons were found in both species and were identified as those of cysK by comparison of deduced amino acid sequences with amino- and carboxyl-terminal amino acid analyses of the S . typhimurium cysK gene product O-acetylserine (thiol)-lyase A . The two cysK DNA sequences were 85% identical, and the deduced amino acid sequences were 96% identical . The major transcription initiation sites for cysK were found to be virtually identical in the two organisms, by using primer extension and S1 nuclease protection techniques . The -35 region corresponding to the major transcription start site was TTCCCC in S . typhimurium and TTCCGC in E . coli . The deviation of these sequences from the consensus sequence TTGACA may reflect the fact that cysK is subject to positive control and requires the cysB regulatory protein for expression . Sequences downstream of cysK were found to include ptsH and a portion of ptsI, thus establishing the exact relationship of cysK with these two genes . A 290-codon open reading frame, which may represent the cysZ gene, was identified upstream of cysK. J Dairy Sci, 1988 Jul, 71(7), 1747 - 55 Separation of immunoglobulins and lactoferrin from cheese whey by chelating chromatography; Al-Mashikhi SA et al.; Different adsorption and chelating chromatographic methods were used to isolate immunoglobulins and lactoferrin from cheese whey . Among three adsorption solid supports (silica, controlled pore glass, and alumina), controlled pore glass showed the highest adsorption of immunoglobulins; however, its capacity was low . 1,4-Butanediol diglycidyl etheriminodiacetic acid on Sepharose 6B was loaded with copper ion and used for the same purpose . Of the two peaks eluted using pH gradient, the first yellowish peak was rich in lactoferrin and the second was rich in Ig . The purity of IgG in the Ig rich fraction as indicated by radial immunodiffusion was 77.2 and 53.0% for acid whey and Cheddar cheese whey, respectively . The capacity of the column was high; a 25-ml copper charged column could absorb Ig from 1 L of cheese whey . Modification of histidine residues in Ig with diethyl pyrocarbonate almost completely eradicated the adsorption, implicating the coordination compound formation between histidine in Ig and Cu on the chelating column as the adsorption mechanism . Enzyme-linked immunosorbent assays of the Ig thus separated demonstrated their binding activity against lipopolysaccharides extracted from Escherichia coli, Salmonella typhimurium, and Bordetella parapertussis. Biochem Pharmacol, 1988 Jul 1, 37(13), 2585 - 93 Preparation, toxicity and mutagenicity of 1-methyl-2-nitrosoimidazole . A toxic 2-nitroimidazole reduction product; Noss MB et al.; 1-Methyl-2-nitrosoimidazole (INO), the 2-electron reduction product of 1-methyl-2-nitroimidazole (INO2), was prepared by electrochemical reduction of INO2 to 2-hydroxylamino-1-methyl-imidazole (INHOH), followed by back oxidation with iodine . Although stable in crystalline form, INO reacted in water, phosphate-buffered saline, and mammalian cell growth medium . Half-lives for decay were determined by UV-visible spectroscopy . INO was found to be highly toxic towards Chinese hamster ovary (CHO) cells, concentrations of 10-60 microM producing significant cytotoxicity . The rate of INO decay was found to be increased in the presence of CHO cells . INO was also toxic and mutagenic towards Salmonella typhimurium TA-100 . When compared on a molar basis to the parent nitro compound INO2, and the 4- and 6-electron reduction products INHOH and 2-amino-1-methylimidazole (INH2), INO was by far (two orders of magnitude) the most toxic under aerobic conditions . These results suggest that the nitroso reduction product of 2-nitroimidazoles may be the reduced species responsible for hypoxic cell selective toxicity of 2-nitroimidazoles. Am J Vet Res, 1988 Jul, 49(7), 1188 - 92 Differential effect of T-2 toxin on murine host resistance to three facultative intracellular bacterial pathogens: Listeria monocytogenes, Salmonella typhimurium, and Mycobacterium bovis; Ziprin RL et al.; The effect of T-2 toxin, a radiomimetic immunosuppressive agent, on resistance to the facultative intracellular bacterial pathogens Listeria monocytogenes (strain EGD), Mycobacterium bovis (BCG Copenhagen 1331), and Salmonella typhimurium was determined . Female Swiss ICR mice were given a single dose of T-2 toxin (4 mg/kg of body weight) by gastric gavage . On the seventh day after toxin administration, the mice were infected by intraperitoneal inoculation with L monocytogenes, S typhimurium, or M bovis . Mice given the toxin also were exposed to respirable droplet nuclei containing L monocytogenes or M bovis . The effect of the toxin on the course of infection was monitored by observing mortality or by enumeration of bacteria in the spleen or lungs of infected mice . The toxin increased resistance to infection with L monocytogenes initiated by intraperitoneal inoculation, but reduced resistance to M bovis infection initiated by intraperitoneal inoculation . The toxin had no appreciable effect on the course of salmonellosis or on resistance to infection initiated by inhalation of L monocytogenes or M bovis aerosols . Therefore, it was concluded that T-2 toxin does not necessarily reduce resistance to infection in mice . The toxin's effect on the course of in vivo bacterial infections depends on the nature of the infective agent and the route of inoculation. Plasmid, 1988 Jul, 20(1), 10 - 6 Genetic and molecular characterization of an epidemic plasmid coding for multidrug resistance in Salmonella typhimurium of human origin; Sharma PL et al.; All 201 multidrug resistant Salmonella typhimurium strains isolated from epidemics in India contained nonconjugative (157 strains) or conjugative (44 strains) Inc F1me multiresistance plasmids . Two small R-plasmids of 7 MDa which coded for resistance to either ampicillin or streptomycin and sulfamethoxazole were also detected along with other plasmids . The small plasmids were members of group 1 and group 2 incompatibility groups . Restriction endonuclease analysis of conjugative (96 MDa) and nonconjugative (88 MDa) Inc F1me plasmids showed considerable similarity except for the presence of unique fragments among both the groups and the loss of fragments corresponding to the smaller size of the nonconjugative plasmid . A single Inc F1me plasmid appears responsible for various outbreaks of multiresistant S . typhimurium in different parts of India. Mutagenesis, 1988 Jul, 3(4), 349 - 53 Mutagenicity of furoquinoline alkaloids in the Salmonella/microsome assay . Mutagenicity of dictamnine is modified by various enzyme inducers and inhibitors; Hafele F et al.; Furoquinoline alkaloids are activated to mutagens by microsomal preparations of rat liver . The mutagenic effects decrease with the increasing number of methoxyl-substituents on the furoquinoline skeleton . After metabolic activation dictamnine, gamma-fagarine and skimmianine exhibit strong mutagenicity in Salmonella typhimurium strains TA98 and TA100 and have comparatively little or no activity in the corresponding non-R-factor strains TA1538 and TA1535 . This indicates that these compounds primarily act as frameshift mutagens . The activation capacity of the metabolizing mixture depends on the amount of microsomal protein . Pretreatment of male Wistar rats with phenobarbital (Pb) or 3-methylcholanthrene results in an increase in the metabolic capacity of the corresponding liver microsome preparations, Pb induction showing the greater effect . Various enzyme inhibitors, such as carbon monoxide, metyrapone, SKF-525A, 7,8-benzoflavone and methimazole, decrease the activation capacities of rat liver preparations, whereas 1,1,1-trichloropropene-2,3-oxide has no effect . These results suggest that furoquinolines are activated to mutagenic metabolites by cytochrome-P-450 and cytochrome-P-448, and possibly by the flavin-containing monooxygenase. Mutagenesis, 1988 Jul, 3(4), 323 - 8 Inter-individual variation in the mutagenic activation of 2-acetylaminofluorene by human liver in relation to animal metabolic models; Smith AJ et al.; A relatively large, reproducible inter-individual variation was found in the ability of 17 human liver S9 samples to mediate the mutagenicity of 2-acetylaminofluorene (2AAF) in Salmonella typhimurium strain TA98 . In an animal model, variation in metabolic activation of 2AAF did not appear to relate to the phenotype of debrisoquine 4-hydroxylase since hepatic S9 from poor and extensive metabolizer phenotypes (female DA and female Wistar rat, respectively) mediated the mutagenicity of this aromatic amide equally well . Approximately one-third of human liver samples exhibited an ability to detoxify 2AAF in a modified bacterial mutagenicity assay in a manner similar to that shown by guinea pig (but not rat or rabbit) S9 . However, only in 2/14 human preparations was the detoxification inhibited by 8-hydroxyquinoline which has previously been recognized as an inhibitor of a detoxifying 'transoxygenation' in guinea pig liver . The results support a growing body of evidence for inter-individual variation in human carcinogen metabolism which may be important in determining susceptibility to chemical carcinogenesis. Mutagenesis, 1988 Jul, 3(4), 303 - 9 Genotoxic activity of the N-acetylated metabolites of the food mutagens 2-amino-3-methylimidazo{4,5-f}quinoline (IQ) and 2-amino-3,4-dimethylimidazo{4,5-f}quinoline (MeIQ); Brunborg G et al.; The genotoxic potential of the food mutagens 2-amino-3-methylimidazo{4,5-f}quinoline (IQ) and 2-amino-3,4-dimethylimidazo{4,5-f}quinoline (MeIQ) and their N-acetylated metabolites (AcIQ and AcMeIQ, respectively) has been studied, in order to evaluate whether an initial N-acetylation of IQ or MeIQ is important for the overall in vivo genotoxicity of the compounds . When incubated with uninduced (control) rat hepatocytes, both the acetylated and the unacetylated compounds appeared to be relatively stable, whereas water-soluble metabolites (i.e . not extractable by ethyl acetate at alkaline pH) were rapidly formed with hepatocytes from PCB-induced animals . No DNA damage was induced by IQ or MeIQ in hepatocytes isolated from control rats, as measured by alkaline elution . In hepatocytes from PCB-pretreated rats, IQ, MeIQ, AcIQ and AcMeIQ induced DNA damage at low (10(-6) M) concentrations, with AcIQ being more potent than IQ whereas AcMeIQ was less potent than MeIQ . Similar patterns were observed when unscheduled DNA synthesis was measured in hepatocytes . The compounds induced sister chromatid exchanges in Chinese hamster V79 cells with PCB-induced hepatocytes as activation system; IQ and AcIQ were equal while AcMeIQ had less activity than MeIQ . The compounds were also compared in bacterial mutagenesis test systems (Salmonella typhimurium TA98) . With hepatocyte activation, AcIQ was slightly more potent than IQ, whereas AcMeIQ was markedly less mutagenic than MeIQ . With subcellular fractions as activation system (rat liver S9 or microsomes), the N-acetylated compounds were similar to or less mutagenic than their parent compounds . The mutagenic effects of AcIQ and AcMeIQ in bacteria with microsomal activation were markedly reduced by the deacetylase inhibitor paraoxon.(ABSTRACT TRUNCATED AT 250 WORDS) Mutagenesis, 1988 Jul, 3(4), 293 - 6 Anti-mutagenicity of catechin against environmental mutagens; Nagabhushan M et al.; Catechu is the non-mutagenic component of betel quid . We have tested catechu extract and catechin for anti-mutagenic activity in Salmonella typhimurium strain TA98 against environmental mutagens relevant to India . Catechu extract, as well as catechin, shows a dose-dependent decrease in the mutagenicity of tobacco and masheri extracts, and bidi and cigarette smoke condensates in TA98 with S9 mix . Mutagenicity of extracts of charred and non-charred meat in TA98 is also inhibited by catechu extract and catechin in a dose-dependent manner with or without S9 mix. Food Chem Toxicol, 1988 Jul, 26(7), 631 - 5 The genotoxic activity of glycerol in an in vitro test battery; Doolittle DJ et al.; Glycerol, a widely distributed constituent of food and an additive used in cigarette manufacture, has been tested for genotoxic potential in a battery of short-term genotoxicity assays . Glycerol was evaluated in the Ames Salmonella typhimurium mutagenesis assay (strains TA98, TA100, TA1535, TA1537 and TA1538), in the rat hepatocyte unscheduled DNA synthesis assay, in the Chinese hamster ovary (CHO) chromosome aberration assay, the CHO sister chromatid exchange assay and the CHO mammalian mutagenesis assay . All assays (except the rat hepatocyte unscheduled DNA synthesis assay) were conducted both with and without the addition of Aroclor-induced rat liver S-9 . The results of all tests were negative, showing that neither glycerol nor its metabolites have genotoxic activity in the battery of tests used. Radiobiologiia, 1988 Jul-Aug, 28(4), 563 - 5 {Biological action of plutonium-239 on Salmonella typhimurium}; Gafieva ZA et al.; Salmonella typhimurium cells were exposed in a 239Pu citrate solution . Cell death and induction of gene mutations were an exponential function of gamma radiation dose . LD37 was 34.8 Gy; mutation doubling dose, 19 Gy. J Bacteriol, 1988 Jul, 170(7), 3032 - 9 Pilin-gene phase variation of Moraxella bovis is caused by an inversion of the pilin genes; Marrs CF et al.; Moraxella bovis Epp63 can express either of two different pilin proteins, called alpha and beta . We have previously cloned and sequenced the beta-pilin gene and now report that DNAs isolated from bacteria expressing alpha pilin have hybridization patterns consistently different from those of bacteria expressing beta pilin . The phase variation between alpha- and beta-pilin gene expression appears to be associated with an inversion of about 2 kilobases of DNA, whose endpoints occur within the coding region of the expressed pilin gene . Comparisons of the beta-pilin gene sequence with those of well-studied bacterial inversion systems revealed a stretch of 58% sequence similarity (21 of 36 base pairs) between the left inverted repeat of the Salmonella typhimurium flagellar hin control region and the amino-terminal portion of the beta-pilin gene. Mol Gen Genet, 1988 Jul, 213(1), 125 - 33 Regulation of proline utilization in Salmonella typhimurium: molecular characterization of the put operon, and DNA sequence of the put control region; Hahn DR et al.; The two genes required for proline utilization (put) in Salmonella typhimurium form a divergent operon . Extensive genetic evidence suggests that transcription of the put operon is autoregulated by the putA gene product, a membrane-associated dehydrogenase . In order to understand the mechanism of regulation, we characterized plasmid clones of the put operon . A 7.5 kb clone contains both of the put structural genes and regulatory sites . This clone only expressed two unique proteins corresponding to the putA and putP gene products . By comparing the physical and genetic maps of the put operon, the position of the put regulatory region was defined and the DNA sequence of this region was determined . Analysis of the DNA sequence indicated several potential regulatory sites for the put genes . Based on genetic and physical mapping studies, the most likely regulatory sites are two convergent promoters approximately 30 bp apart . A 27 bp palindrome located between the two promoters may be the operator for autoregulation by the PutA protein . The putA translational start site is 40 bp downstream of its putative mRNA start site . The putP promoter and its translational start site are separated by a 400 bp untranslated region. Zh Mikrobiol Epidemiol Immunobiol, 1988 Jul, (7), 9 - 11 {Effect of cyclic 3,5-adenosine monophosphate on the virulence of Salmonella typhimurium}; Boichenko MN et al.; To study the role of cAMP in the virulence of S . typhimurium, cAMP-producing plasmid pTG 4 was transferred to cAMP-deficient S . typhimurium mutant . The transfer of the plasmid enhanced the virulence of the microorganisms due to the increased destruction of macrophages and the intensified multiplication of salmonellae in the spleen of mice. J Bacteriol, 1988 Jul, 170(7), 3243 - 8 Structure of the gene encoding phosphoribosylpyrophosphate synthetase (prsA) in Salmonella typhimurium; Bower SG et al.; The Salmonella typhimurium gene prsA, which encodes phosphoribosylpyrophosphate synthetase, has been cloned, and the nucleotide sequence has been determined . The amino acid sequence derived from the S . typhimurium gene is 99% identical to the derived Escherichia coli sequence and 47% identical to two rat isozyme sequences . Strains containing plasmid-borne prsA have been used to overproduce and purify the enzyme . The promoter for the S . typhimurium prsA gene was identified by deletion analysis and by similarity to the promoter for the E . coli prsA gene . The location of the prsA promoter results in a 416-base-pair 5' untranslated leader in the prsA transcript, which was shown by deletion to be necessary for maximal synthesis of phosphoribosylpyrophosphate synthetase . The S . typhimurium leader contains a 115-base-pair insert relative to the E . coli leader . The insert appears to have no functional significance. J Bacteriol, 1988 Jul, 170(7), 3223 - 7 Expression of the divergent tricarboxylate transport operon (tctI) of Salmonella typhimurium; Widenhorn KA et al.; Membrane-associated gene products of shock-sensitive bacterial transport operons are often difficult to detect . A 4.5-kilobase DNA fragment, known to completely encode the Salmonella typhimurium tctI operon, was cloned in both orientations behind the T7 phage promoter phi 10 and expressed by using the T7 polymerase-promoter system of Tabor and Richardson (S . Tabor and C . C . Richardson, Proc . Natl . Acad . Sci . USA 82:1074-1078, 1985) . Under these conditions, five proteins were clearly demonstrated . One DNA strand was shown to encode the periplasmic (29,000-Mr) C protein (as a 31,000-Mr precursor), a 19,000-Mr protein, and a 40,000- to 45,000-Mr protein which ran as a diffuse band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis . The opposite strand carried the information for two additional proteins of 29,000 and 14,000 Mr . By Tn5 mutagenesis, subcloning of Tn5 insertions, and subcloning of various deletion mutants it was shown that the tctI system is divergently transcribed . The periplasmic binding protein (C protein) is the first product of one operon, followed by the 19,000-Mr and 45,000-Mr integral inner membrane proteins . On the opposite strand only the 29,000-Mr protein was essential for tctI function, and it was found to be weakly attached to the inner membrane . Thus tctI encodes four proteins, one periplasmic, two integral, and one peripheral to the cytoplasmic membrane, with the genes arranged as tctA tctB tctC tctD. J Bacteriol, 1988 Jul, 170(7), 3115 - 24 Molecular cloning and characterization of supQ/newD, a gene substitution system for the leuD gene of Salmonella typhimurium; Stover CK et al.; The isopropylmalate isomerase of Salmonella typhimurium and Escherichia coli is a complex of the leuC and leuD gene products . The supQ/new D gene substitution system in S . typhimurium restores leucine prototrophy to leuD mutants of S . typhimurium . Previous genetic evidence supports a model that indicates the replacement of the missing LeuD polypeptide by the newD gene product . This model proposed that this gene substitution is possible when a mutation at the supQ locus (near newD) liberates unaltered newD polypeptide from its normal complex with the supQ protein product . In this study, recombinant plasmids carrying newD, supQ, or both were transformed into E . coli and S . typhimurium strains deleted for the leuD and supQ genes to test the supQ/newD gene substitution model for suppression of leucine auxotrophy . It was determined that the newD gene encodes a 22-kilodalton polypeptide which can restore leucine prototrophy to leuD deletion strains and that a functional supQ gene prevents this suppression . It was also determined that the supQ and newD genes are separated by a gene encoding a 50-kilodalton protein, pB . While there is extensive DNA sequence homology between the leucine operons of S . typhimurium and E . coli, DNA hybridization experiments did not indicate substantial homology between the newD and leuD genes . These data, taken together with previously obtained genetic data, eliminate the possibility that supQ and newD are recently translocated segments of the leucine operon. J Mol Biol, 1988 Jun 20, 201(4), 663 - 73 Structure and expression of the ompB operon, the regulatory locus for the outer membrane porin regulon in Salmonella typhimurium LT-2; Liljestrom P et al.; The ompB operon of Salmonella typhimurium encodes a positive transcriptional regulator OmpR and an inner membrane protein EnvZ . Both proteins are needed for the proper expression of the outer membrane proteins OmpC and OmpF . We have determined the nucleotide sequence of the ompB locus and its adjacent regions . A comparison between the S . typhimurium and Escherichia coli sequences revealed that the ompB locus is highly conserved . The sequence data also showed that ompR and envZ form an operon, where the coding regions overlap by four base-pairs . Utilizing ompR-lacZ and envZ-lacZ gene fusions, the translational levels of expression of these two genes were measured, showing that ompR is considerably more efficiently expressed than envZ . Analysis of ompR frameshift mutations showed that tra