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10200.7051Paradoxical behaviour of pKM101; inhibition of uvr-independent crosslink repair in Escherichia coli by muc gene products. In strains of Escherichia coli deficient in excision repair (uvrA or uvrB), plasmid pKM101 muc+ but not pGW219 mucB::Tn5 enhanced resistance to angelicin monoadducts but reduced resistance to 8-methoxy-psoralen interstrand DNA crosslinks. Thermally induced recA-441 (= tif-1) bacteria showed an additional resistance to crosslinks that was blocked by pKM101. Plasmid-borne muc+ genes also conferred some additional sensitivity to gamma-radiation and it is suggested that a repair step susceptible to inhibition by muc+ gene products and possibly involving double-strand breaks may be involved after both ionizing radiation damage and psoralen crosslinks.19853883148
55510.7045Mutations in dsbA and dsbB, but not dsbC, lead to an enhanced sensitivity of Escherichia coli to Hg2+ and Cd2+. The Dsb proteins are involved in disulfide bond formation, reduction and isomerisation in a number of Gram-negative bacteria. Mutations in dsbA or dsbB, but not dsbC, increase the proportion of proteins with free thiols in the periplasm compared to wild-type. We investigated the effects of mutations in these genes on the bacterial resistance to mercuric and cadmium salts. Mutations in genes involved primarily in disulfide formation (dsbA and dsbB) generally enhanced the sensitivity to Hg2+ and Cd2+ while a mutation of the dsbC gene (primarily an isomerase of disulfide bonds) had no effect. Mutations of the dsb genes had no effect on the expression of the mercury-resistance determinants of the transposon Tn501.199910234837
52820.7000Effect of dimethyl sulphoxide on the expression of nitrogen fixation in bacteria. Storage in dimethyl sulphoxide (DMSO) of Escherichia coli K12 hybrids carrying nif+ genes from Klebsiella pneumoniae can result in selection of a defective nitrogen-fixing phenotype. Similar results are obtained with E. coli K12 hybrids containing the nitrogen-fixing capacity from Rhizobium trifolii. DMSO appears to affect particular inner membrane proteins associated with energy metabolism in E. coli K12 and four chromosomal regions (chlD, chlG, his and unc) are associated with resistance to DMSO.1977332135
80230.6970YqhC regulates transcription of the adjacent Escherichia coli genes yqhD and dkgA that are involved in furfural tolerance. Previous results have demonstrated that the silencing of adjacent genes encoding NADPH-dependent furfural oxidoreductases (yqhD dkgA) is responsible for increased furfural tolerance in an E. coli strain EMFR9 [Miller et al., Appl Environ Microbiol 75:4315-4323, 2009]. This gene silencing is now reported to result from the spontaneous insertion of an IS10 into the coding region of yqhC, an upstream gene. YqhC shares homology with transcriptional regulators belonging to the AraC/XylS family and was shown to act as a positive regulator of the adjacent operon encoding YqhD and DkgA. Regulation was demonstrated by constructing a chromosomal deletion of yqhC, a firefly luciferase reporter plasmid for yqhC, and by a direct comparison of furfural resistance and NADPH-dependent furfural reductase activity. Closely related bacteria contain yqhC, yqhD, and dkgA orthologs in the same arrangement as in E. coli LY180. Orthologs of yqhC are also present in more distantly related Gram-negative bacteria. Disruption of yqhC offers a useful approach to increase furfural tolerance in bacteria.201120676725
53840.6912The biochemical and genetic basis for high frequency thiomethyl galactoside resistance in lambda,lambdadg lysogens of Escherichia coli. In a culture of Escherichia coli K12 gal (lambdadg), cells which form large colonies on agar plates containing galactose and thiomethyl beta-D-galactoside (TMG) appear at high frequency. These clones are resistant to growth inhibition by TMG on galactose minimal medium. Biochemical studies of the steady-state levels of galactokinase and UDPgalactose 4-epimerase suggest that the resistant clones have extra copies of the genes for the galactose-metabolizing enzymes. The mutation for TMG resistance is not located in either the bacterial or the bacteriophage genome, but is probably due to an aberrant association between cell and prophage DNA. Mapping the TMG-resistant characteristic by phage P1 indicates that TMG-resistant bacteria posses at least two GAL+ OPERONS, ONE OF WHICH IS COTRANSDUCIBLe with bio+. In addition, TMG-resistant bacteria behave like lambdadg polylysogens when challenged with the phage lambdaI90c17. From these genetic experiments we conclude that TMG-resistant bacteria arise by duplication of the lambdadg prophage. Finally, gal+ bacteria which carry a single, additional, lambdadg prophage are TMG-resistant. TMG resistance is probably a gal+ gene dosage effect.1978344832
32850.6902Multiresistance genes of Rhizobium etli CFN42. Multidrug efflux pumps of bacteria are involved in the resistance to various antibiotics and toxic compounds. In Rhizobium etli, a mutualistic symbiont of Phaseolus vulgaris (bean), genes resembling multidrug efflux pump genes were identified and designated rmrA and rmrB. rmrA was obtained after the screening of transposon-generated fusions that are inducible by bean-root released flavonoids. The predicted gene products of rmrAB shared significant homology to membrane fusion and major facilitator proteins, respectively. Mutants of rmrA formed on average 40% less nodules in bean, while mutants of rmrA and rmrB had enhanced sensitivity to phytoalexins, flavonoids, and salicylic acid, compared with the wild-type strain. Multidrug resistance genes emrAB from Escherichia coli complemented an rmrA mutant from R. etli for resistance to high concentrations of naringenin.200010796024
50360.6895Interaction of the chromosomal Tn 551 with two thermosensitive derivatives, pS1 and p delta D, of the plasmid pI9789 in Staphylococcus aureus. The plasmid pI9789::Tn552 carries genes conferring resistance to penicillins and to cadmium, mercury and arsenate ions. The presence of Tn551 at one location in the chromosome of Staphylococcus aureus enhances the frequency of suppression of thermosensitivity of replication of the plasmids pS1 and p delta D which are derivatives of pI9789::Tn552. Bacteriophage propagated on the bacteria in which thermosensitivity of replication had been suppressed was used to transduce cadmium resistance to S. aureus PS80N. The cadmium-resistant transductants obtained carried plasmid pS1 or p delta D with a copy of Tn551 inserted into a specific site on pS1 but into several different sites on p delta D. The possible mechanisms of the suppression are discussed.19957758929
4670.6890The pepper Bs4C proteins are localized to the endoplasmic reticulum (ER) membrane and confer disease resistance to bacterial blight in transgenic rice. Transcription activator-like effector (TALE)-dependent dominant disease resistance (R) genes in plants, also referred to as executor R genes, are induced on infection by phytopathogenic bacteria of the genus Xanthomonas harbouring the corresponding TALE genes. Unlike the traditional R proteins, the executor R proteins do not determine the resistance specificity and may function broadly in different plant species. The executor R gene Bs4C-R in the resistant genotype PI 235047 of the pepper species Capsicum pubescens (CpBs4C-R) confers disease resistance to Xanthomonas campestris pv. vesicatoria (Xcv) harbouring the TALE genes avrBsP/avrBs4. In this study, the synthetic genes of CpBs4C-R and two other Bs4C-like genes, the susceptible allele in the genotype PI585270 of C. pubescens (CpBs4C-S) and the CaBs4C-R homologue gene in the cultivar 'CM334' of Capsicum annum (CaBs4C), were characterized in tobacco (Nicotiana benthamiana) and rice (Oryza sativa). The Bs4C genes induced cell death in N. benthamiana. The functional Bs4C-eCFP fusion proteins were localized to the endoplasmic reticulum (ER) membrane in the leaf epidermal cells of N. benthamiana. The Xa10 promoter-Bs4C fusion genes in transgenic rice conferred strain-specific disease resistance to Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial blight in rice, and were specifically induced by the Xa10-incompatible Xoo strain PXO99(A) (pHM1avrXa10). The results indicate that the Bs4C proteins from pepper species function broadly in rice and the Bs4C protein-mediated cell death from the ER is conserved between dicotyledonous and monocotyledonous plants, which can be utilized to engineer novel and enhanced disease resistance in heterologous plants.201829603592
32980.6889Effect of NlpE overproduction on multidrug resistance in Escherichia coli. NlpE, an outer membrane lipoprotein, functions during envelope stress responses in Gram-negative bacteria. In this study, we report that overproduction of NlpE increases multidrug and copper resistance through activation of the genes encoding the AcrD and MdtABC multidrug efflux pumps in Escherichia coli.201020211889
53490.6886Plasmid shuttle vector with two insertionally inactivable markers for coryneform bacteria. A new shuttle vector pCEM500 replicating in Escherichia coli and in Brevibacterium flavum was constructed. It carries two antibiotic resistance determinants (Kmr/Gmr from plasmid pSa of Gram-negative bacteria and Smr/Spr from plasmid pCG4 of Corynebacterium glutamicum) which are efficiently expressed in both hosts and can be inactivated by insertion of DNA fragments into the unique restriction endonuclease sites located within them. This vector was found to be stably maintained in B. flavum and can be used for transfer of the cloned genes into this amino-acid-producing coryneform bacterium.19902148164
556100.6875An ArsR/SmtB family member regulates arsenic resistance genes unusually arranged in Thermus thermophilus HB27. Arsenic resistance is commonly clustered in ars operons in bacteria; main ars operon components encode an arsenate reductase, a membrane extrusion protein, and an As-sensitive transcription factor. In the As-resistant thermophile Thermus thermophilus HB27, genes encoding homologues of these proteins are interspersed in the chromosome. In this article, we show that two adjacent genes, TtsmtB, encoding an ArsR/SmtB transcriptional repressor and, TTC0354, encoding a Zn(2+) /Cd(2+) -dependent membrane ATPase are involved in As resistance; differently from characterized ars operons, the two genes are transcribed from dedicated promoters upstream of their respective genes, whose expression is differentially regulated at transcriptional level. Mutants defective in TtsmtB or TTC0354 are more sensitive to As than the wild type, proving their role in arsenic resistance. Recombinant dimeric TtSmtB binds in vitro to both promoters, but its binding capability decreases upon interaction with arsenate and, less efficiently, with arsenite. In vivo and in vitro experiments also demonstrate that the arsenate reductase (TtArsC) is subjected to regulation by TtSmtB. We propose a model for the regulation of As resistance in T. thermophilus in which TtSmtB is the arsenate sensor responsible for the induction of TtArsC which generates arsenite exported by TTC0354 efflux protein to detoxify cells.201728696001
529110.6867Crystal structure of the transcriptional repressor PagR of Bacillus anthracis. PagR is a transcriptional repressor in Bacillus anthracis that controls the chromosomal S-layer genes eag and sap, and downregulates the protective antigen pagA gene by direct binding to their promoter regions. The PagR protein sequence is similar to those of members of the ArsR repressor family involved in the repression of arsenate-resistance genes in numerous bacteria. The crystal structure of PagR was solved using multi-wavelength anomalous diffraction (MAD) techniques and was refined with 1.8 A resolution diffraction data. The PagR molecules form dimers, as observed in all SmtB/ArsR repressor family proteins. In the crystal lattice four PagR dimers pack together to form an inactive octamer. Model-building studies suggest that the dimer binds to a DNA duplex with a bend of around 4 degrees.201019926656
540120.6865Effect of ogt expression on mutation induction by methyl-, ethyl- and propylmethanesulphonate in Escherichia coli K12 strains. We have previously reported the isolation of an Escherichia coli K12 mutant that is extremely sensitive to mutagenesis by low doses of ethylating agents. We now show by Southern analysis that the mutation involves a gross deletion covering at least the ogt and fnr genes and that no O6-alkylguanine-DNA-alkyltransferase activity is present in cell-free extracts of an ada::Tn10 derivative of these bacteria. Confirmation that sensitisation to ethylation-induced mutagenesis was attributable to ogt and not to any other loci covered by the deletion was obtained by constructing derivatives. Thus an ogt::kanr disruption mutation was introduced into the parental ogt+ bacteria, and the ogt::kanr mutation was then eliminated by cotransduction of ogt+ with the closely linked Tetr marker (zcj::Tn10). The delta(ogt-fnr) deletion or ogt::kanr disruption mutants were highly sensitive to ethyl methanesulphonate-induced mutagenesis, as measured by the induction of forward mutations to L-arabinose resistance (Arar). Furthermore, the number of Arar mutants increased linearly with dose, unlike the case in ogt+ bacteria, which had a threshold dose below which no mutants accumulated. Differences in mutability were even greater with propyl methanesulphonate. Overproduction of the ogt alkyltransferase from a multicopy plasmid reduced ethylmethanesulphonate-induced mutagenesis in the ogt- mutant strains and also methylmethanesulphonate mutagenesis in ada- bacteria. A sample of AB1157 obtained from the E. coli K12 genetic stock centre also had a deletion covering the ogt and fnr genes. Since such deletions greatly influence the mutagenic responses to alkylating agents, a survey of the presence of the ogt gene in the E. coli K12 strain being used is advisable.19948152424
6012130.6865Metal resistance-related genes are differently expressed in response to copper and zinc ion in six Acidithiobacillus ferrooxidans strains. Metal resistance of acidophilic bacteria is very significant during bioleaching of copper ores since high concentration of metal is harmful to the growth of microorganisms. The resistance levels of six Acidithiobacillus ferrooxidans strains to 0.15 M copper and 0.2 M zinc were investigated, and eight metal resistance-related genes (afe-0022, afe-0326, afe-0329, afe-1143, afe-0602, afe-0603, afe-0604, and afe-1788) were sequenced and analyzed. The transcriptional expression levels of eight possible metal tolerance genes in six A. ferrooxidans strains exposed to 0.15 M Cu(2+) and 0.2 M Zn(2+) were determined by real-time quantitative PCR (RT-qPCR), respectively. The copper resistance levels of six A. ferrooxidans strains declined followed by DY26, DX5, DY15, GD-B, GD-0, and YTW. The zinc tolerance levels of six A. ferrooxidans strains exposed to 0.2 M Zn(2+) from high to low were YTW > GD-B > DY26 > GD-0 > DX5 > DY15. Seven metal tolerance-related genes all presented in the genome of six strains, except afe-0604. The metal resistance-related genes showed different transcriptional expression patterns in six A. ferrooxidans strains. The expression of gene afe-0326 and afe-0022 in six A. ferrooxidans strains in response to 0.15 M Cu(2+) showed the same trend with the resistance levels. The expression levels of genes afe-0602, afe-0603, afe-0604, and afe-1788 in six strains response to 0.2 M Zn(2+) did not show a clear correlation between the zinc tolerance levels of six strains. According to the results of RT-qPCR and bioinformatics analysis, the proteins encoded by afe-0022, afe-0326, afe-0329, and afe-1143 were related to Cu(2+) transport of A. ferrooxidans strains.201425023638
576140.6861Caenorhabditis elegans defective-pharynx and constipated mutants are resistant to Orsay virus infection. C. elegans animals with a compromised pharynx accumulate bacteria in their intestinal lumen and activate a transcriptional response that includes anti-bacterial response genes. In this study, we demonstrate that animals with defective pharynxes are resistant to Orsay virus (OrV) infection. This resistance is observed for animals grown on Escherichia coli OP50 and on Comamonas BIGb0172, a bacterium naturally associated with C. elegans . The viral resistance observed in defective-pharynx mutants does not seem to result from constitutive transcriptional immune responses against viruses. OrV resistance is also observed in mutants with defective defecation, which share with the pharynx-defective perturbations in the regulation of their intestinal contents and altered lipid metabolism. The underlying mechanisms of viral resistance in pharynx- and defecation-defective mutants remain elusive.202438590801
6009150.6858Efflux pump inhibitor chlorpromazine effectively increases the susceptibility of Escherichia coli to antimicrobial peptide Brevinin-2CE. Aim: The response of E. coli ATCC8739 to Brevinin-2CE (B2CE) was evaluated as a strategy to prevent the development of antimicrobial peptide (AMP)-resistant bacteria. Methods: Gene expression levels were detected by transcriptome sequencing and RT-PCR. Target genes were knocked out using CRISPR-Cas9. MIC was measured to evaluate strain resistance. Results: Expression of acrZ and sugE were increased with B2CE stimulation. ATCC8739ΔacrZ and ATCC8739ΔsugE showed twofold and fourfold increased sensitivity, respectively. The survival rate of ATCC8739 was reduced in the presence of B2CE/chlorpromazine (CPZ). Combinations of other AMPs with CPZ also showed antibacterial effects. Conclusion: The results indicate that combinations of AMPs/efflux pump inhibitors (EPIs) may be a potential approach to combat resistant bacteria.202438683168
545160.6853Characterization of the organic hydroperoxide resistance system of Brucella abortus 2308. The organic hydroperoxide resistance protein Ohr has been identified in numerous bacteria where it functions in the detoxification of organic hydroperoxides, and expression of ohr is often regulated by a MarR-type regulator called OhrR. The genes annotated as BAB2_0350 and BAB2_0351 in the Brucella abortus 2308 genome sequence are predicted to encode OhrR and Ohr orthologs, respectively. Using isogenic ohr and ohrR mutants and lacZ promoter fusions, it was determined that Ohr contributes to resistance to organic hydroperoxide, but not hydrogen peroxide, in B. abortus 2308 and that OhrR represses the transcription of both ohr and ohrR in this strain. Moreover, electrophoretic mobility shift assays and DNase I footprinting revealed that OhrR binds directly to a specific region in the intergenic region between ohr and ohrR that shares extensive nucleotide sequence similarity with so-called "OhrR boxes" described in other bacteria. While Ohr plays a prominent role in protecting B. abortus 2308 from organic hydroperoxide stress in in vitro assays, this protein is not required for the wild-type virulence of this strain in cultured murine macrophages or experimentally infected mice.201222821968
333170.6851Mutants of Escherichia coli altered in both genes coding for the elongation factor Tu. Genetic analysis of a mutant of Escherichia coli resistant to the antibiotic mocimycin is presented. This resistance is due to alterations in both tuf genes coding for the elongation factor Tu. Mocimycin resistance is recessive. Bacteria carryong only one tuf gene from the resistant mutant are still mocimycin sensitive. If the mutant gene is the tufA gene, the seisitive cells can be made resistant through inactivation of the tufB gene by insertion of the bacteriophage milliunits genome. Conditional mocimycin-resistant mutants ban also be isolated when the tufB gene is altered by an amber or a temperature-sensitive mutation. When only the tufB allele from the original mocimycin-resistant mutant is present, inactivation of the wild-type tufA gene fails to give viable mocimycin-resistant progeny. We conclude that the tufA mutant allele codes for a functional mocimycin-resistant EF-Tu, whereas the mutant tufB gene does not code for a functional product.1978360222
502180.6844A highly specialized flavin mononucleotide riboswitch responds differently to similar ligands and confers roseoflavin resistance to Streptomyces davawensis. Streptomyces davawensis is the only organism known to synthesize the antibiotic roseoflavin, a riboflavin (vitamin B2) analog. Roseoflavin is converted to roseoflavin mononucleotide (RoFMN) and roseoflavin adenine dinucleotide in the cytoplasm of target cells. (Ribo-)Flavin mononucleotide (FMN) riboswitches are genetic elements, which in many bacteria control genes responsible for the biosynthesis and transport of riboflavin. Streptomyces davawensis is roseoflavin resistant, and the closely related bacterium Streptomyces coelicolor is roseoflavin sensitive. The two bacteria served as models to investigate roseoflavin resistance of S. davawensis and to analyze the mode of action of roseoflavin in S. coelicolor. Our experiments demonstrate that the ribB FMN riboswitch of S. davawensis (in contrast to the corresponding riboswitch of S. coelicolor) is able to discriminate between the two very similar flavins FMN and RoFMN and shows opposite responses to the latter ligands.201222740651
547190.6841Dual role of OhrR as a repressor and an activator in response to organic hydroperoxides in Streptomyces coelicolor. Organic hydroperoxide resistance in bacteria is achieved primarily through reducing oxidized membrane lipids. The soil-inhabiting aerobic bacterium Streptomyces coelicolor contains three paralogous genes for organic hydroperoxide resistance: ohrA, ohrB, and ohrC. The ohrA gene is transcribed divergently from ohrR, which encodes a putative regulator of MarR family. Both the ohrA and ohrR genes were induced highly by various organic hydroperoxides. The ohrA gene was induced through removal of repression by OhrR, whereas the ohrR gene was induced through activation by OhrR. Reduced OhrR bound to the ohrA-ohrR intergenic region, which contains a central (primary) and two adjacent (secondary) inverted-repeat motifs that overlap with promoter elements. Organic peroxide decreased the binding affinity of OhrR for the primary site, with a concomitant decrease in cooperative binding to the adjacent secondary sites. The single cysteine C28 in OhrR was involved in sensing oxidants, as determined by substitution mutagenesis. The C28S mutant of OhrR bound to the intergenic region without any change in binding affinity in response to organic peroxides. These results lead us to propose a model for the dual action of OhrR as a repressor and an activator in S. coelicolor. Under reduced conditions, OhrR binds cooperatively to the intergenic region, repressing transcription from both genes. Upon oxidation, the binding affinity of OhrR decreases, with a concomitant loss of cooperative binding, which allows RNA polymerase to bind to both the ohrA and ohrR promoters. The loosely bound oxidized OhrR can further activate transcription from the ohrR promoter.200717586628