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52800.7485Effect 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
10210.7391Paradoxical 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
59220.7376Metabolism of Tryptophan and Tryptophan Analogs by Rhizobium meliloti. The alfalfa symbiont Rhizobium meliloti Rm1021 produces indole-3-acetic acid in a regulated manner when supplied with exogenous tryptophan. Mutants with altered response to tryptophan analogs still produce indole-3-acetic acid, but are Fix(-) because bacteria do not fully differentiate into the nitrogen-fixing bacteriod form. These mutations are in apparently essential genes tightly linked to a dominant streptomycin resistance locus.199016667364
10330.7368IL-1 receptor regulates S100A8/A9-dependent keratinocyte resistance to bacterial invasion. Previously, we reported that epithelial cells respond to exogenous interleukin (IL)-1α by increasing expression of several genes involved in the host response to microbes, including the antimicrobial protein complex calprotectin (S100A8/A9). Given that S100A8/A9 protects epithelial cells against invading bacteria, we studied whether IL-1α augments S100A8/A9-dependent resistance to bacterial invasion of oral keratinocytes. When inoculated with Listeria monocytogenes, human buccal epithelial (TR146) cells expressed and released IL-1α. Subsequently, IL-1α-containing media from Listeria-infected cells increased S100A8/A9 gene expression in naïve TR146 cells an IL-1 receptor (IL-1R)-dependent manner. Incubation with exogenous IL-1α decreased Listeria invasion into TR146 cells, whereas invasion increased with IL-1R antagonist. Conversely, when S100A8/A9 genes were knocked down using short hairpin RNA (shRNA), TR146 cells responded to exogenous IL-1α with increased intracellular bacteria. These data strongly suggest that infected epithelial cells release IL-1α to signal neighboring keratinocytes in a paracrine manner, promoting S100A8/A9-dependent resistance to invasive L. monocytogenes.201222031183
53040.7360Location of the genes for anthranilate synthase in Streptomyces venezuelae ISP5230: genetic mapping after integration of the cloned genes. The anthranilate synthase (trpEG) genes in Streptomyces venezuelae ISP5230 were located by allowing a segregationally unstable plasmid carrying cloned S. venezuelae trpEG DNA and a thiostrepton resistance (tsr) marker to integrate into the chromosome. The integrated tsr was mapped by conjugation and transduction to a location close to tyr-2, between arg-6 and trpA13. A genomic DNA fragment containing trpC from S. venezuelae ISP5230 was cloned by complementation of a trpC mutation in Streptomyces lividans. Evidence from restriction enzyme analysis of the cloned DNA fragments, from Southern hybridization using the cloned trp DNA as probes, and from cotransduction frequencies, placed trpEG at a distance of 12-45 kb from the trpCBA cluster. The overall arrangement of tryptophan biosynthesis genes in the S. venezuelae chromosome differs from that in other bacteria examined so far.19938515229
55850.7353Thiamine pyrophosphate riboswitches are targets for the antimicrobial compound pyrithiamine. Thiamine metabolism genes are regulated in numerous bacteria by a riboswitch class that binds the coenzyme thiamine pyrophosphate (TPP). We demonstrate that the antimicrobial action of the thiamine analog pyrithiamine (PT) is mediated by interaction with TPP riboswitches in bacteria and fungi. For example, pyrithiamine pyrophosphate (PTPP) binds the TPP riboswitch controlling the tenA operon in Bacillus subtilis. Expression of a TPP riboswitch-regulated reporter gene is reduced in transgenic B. subtilis or Escherichia coli when grown in the presence of thiamine or PT, while mutant riboswitches in these organisms are unresponsive to these ligands. Bacteria selected for PT resistance bear specific mutations that disrupt ligand binding to TPP riboswitches and derepress certain TPP metabolic genes. Our findings demonstrate that riboswitches can serve as antimicrobial drug targets and expand our understanding of thiamine metabolism in bacteria.200516356850
80260.7347YqhC 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
52970.7343Crystal 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
57780.7316The SIR2 gene family, conserved from bacteria to humans, functions in silencing, cell cycle progression, and chromosome stability. Genomic silencing is a fundamental mechanism of transcriptional regulation, yet little is known about conserved mechanisms of silencing. We report here the discovery of four Saccharomyces cerevisiae homologs of the SIR2 silencing gene (HSTs), as well as conservation of this gene family from bacteria to mammals. At least three HST genes can function in silencing; HST1 overexpression restores transcriptional silencing to a sir2 mutant and hst3 hst4 double mutants are defective in telomeric silencing. In addition, HST3 and HST4 together contribute to proper cell cycle progression, radiation resistance, and genomic stability, establishing new connections between silencing and these fundamental cellular processes.19957498786
81490.7311Drown Them in Their Own Garbage: a New Strategy To Reverse Polymyxin Resistance? Purcell and colleagues offer new insights into a major mechanism of polymyxin resistance in Gram-negative bacteria (A. B. Purcell, B. J. Voss, and M. S. Trent, J Bacteriol 204:e00498-21, 2022, https://doi.org/10.1128/JB.00498-21). Inactivating a single lipid recycling enzyme causes accumulation of waste lipid by-products that inhibit a key factor responsible for polymyxin resistance.202234843378
110100.7308Resistance to the macrolide antibiotic tylosin is conferred by single methylations at 23S rRNA nucleotides G748 and A2058 acting in synergy. The macrolide antibiotic tylosin has been used extensively in veterinary medicine and exerts potent antimicrobial activity against Gram-positive bacteria. Tylosin-synthesizing strains of the Gram-positive bacterium Streptomyces fradiae protect themselves from their own product by differential expression of four resistance determinants, tlrA, tlrB, tlrC, and tlrD. The tlrB and tlrD genes encode methyltransferases that add single methyl groups at 23S rRNA nucleotides G748 and A2058, respectively. Here we show that methylation by neither TlrB nor TlrD is sufficient on its own to give tylosin resistance, and resistance is conferred by the G748 and A2058 methylations acting together in synergy. This synergistic mechanism of resistance is specific for the macrolides tylosin and mycinamycin that possess sugars extending from the 5- and 14-positions of the macrolactone ring and is not observed for macrolides, such as carbomycin, spiramycin, and erythromycin, that have different constellations of sugars. The manner in which the G748 and A2058 methylations coincide with the glycosylation patterns of tylosin and mycinamycin reflects unambiguously how these macrolides fit into their binding site within the bacterial 50S ribosomal subunit.200212417742
344110.7307Identification of genes in Rhizobium leguminosarum bv. trifolii whose products are homologues to a family of ATP-binding proteins. The specific interaction between rhizobia and their hosts requires many genes that influence both early and late steps in symbiosis. Three new genes, designated prsD, prsE (protein secretion) and orf3, were identified adjacent to the exo133 mutation in a cosmid carrying the genomic DNA of Rhizobium leguminosarum bv. trifolii TA1. The prsDE genes share significant homology to the genes encoding ABC transporter proteins PrtDE from Erwinia chrysanthemi and AprDE from Pseudomonas aeruginosa which export the proteases in these bacteria. PrsD shows at least five potential transmembrane hydrophobic regions and a large hydrophilic domain containing an ATP/GTP binding cassette. PrsE has only one potential transmembrane hydrophobic domain in the N-terminal part and is proposed to function as an accessory factor in the transport system. ORF3, like PrtF and AprF, has a typical N-terminal signal sequence but has no homology to these proteins. The insertion of a kanamycin resistance cassette into the prsD gene of the R. leguminosarum bv. trifolii TA1 wild-type strain created a mutant which produced a normal amount of exopolysaccharide but was not effective in the nodulation of clover plants.19979141701
533120.7303Construction of broad-host-range cosmid cloning vectors: identification of genes necessary for growth of Methylobacterium organophilum on methanol. Four new cloning vectors have been constructed from the broad-host-range cloning vector pRK290. These vectors, pLA2901, pLA2905, pLA2910, and pLA2917, confer resistance to kanamycin and tetracycline. The latter two are cosmid derivatives of pLA2901. The new vectors can be mobilized into, and are stably maintained in, a variety of gram-negative bacteria. A Sau3A genomic bank of Methylobacterium organophilum strain xx DNA has been constructed in pLA2917, and complementation analysis, with a variety of mutants unable to grow on methanol, revealed at least five separate regions necessary for growth on methanol. Complementation analysis and Tn5 mutagenesis data suggest that at least three genes are responsible for expression of active methanol dehydrogenase.19852982796
609130.7297A metazoan ortholog of SpoT hydrolyzes ppGpp and functions in starvation responses. In nutrient-starved bacteria, RelA and SpoT proteins have key roles in reducing cell growth and overcoming stresses. Here we identify functional SpoT orthologs in metazoa (named Mesh1, encoded by HDDC3 in human and Q9VAM9 in Drosophila melanogaster) and reveal their structures and functions. Like the bacterial enzyme, Mesh1 proteins contain an active site for ppGpp hydrolysis and a conserved His-Asp-box motif for Mn(2+) binding. Consistent with these structural data, Mesh1 efficiently catalyzes hydrolysis of guanosine 3',5'-diphosphate (ppGpp) both in vitro and in vivo. Mesh1 also suppresses SpoT-deficient lethality and RelA-induced delayed cell growth in bacteria. Notably, deletion of Mesh1 (Q9VAM9) in Drosophila induces retarded body growth and impaired starvation resistance. Microarray analyses reveal that the amino acid-starved Mesh1 null mutant has highly downregulated DNA and protein synthesis-related genes and upregulated stress-responsible genes. These data suggest that metazoan SpoT orthologs have an evolutionarily conserved function in starvation responses.201020818390
109140.7296Identification of two putative ATP-cassette genes in Encephalitozoon intestinalis. Currently existing chemotherapeutic compounds are limited and few are effective for treating microsporidiosis. It is possible that resistance of Encephalitozoon to some drugs occurs by efflux mechanisms similar to those previously described for mammalian tumour cells, bacteria or protozoal parasites such as Plasmodium, Leishmania and Entamoeba histolytica. The data in the present study suggest that Encephalitozoon intestinalis contains at least one multidrug resistance gene. We report here two complete sequences EiABC1 and EiABC2, encoding different ATP-binding cassette genes from E. intestinalis, including a P-gp.200111730796
507150.7293Tellurite resistance and reduction by obligately aerobic photosynthetic bacteria. Seven species of obligately aerobic photosynthetic bacteria of the genera Erythromicrobium, Erythrobacter, and Roseococcus demonstrated high-level resistance to tellurite and accumulation of metallic tellurium crystals. High-level resistance without tellurite reduction was observed for Roseococcus thiosulfatophilus and Erythromicrobium ezovicum grown with certain organic carbon sources, implying that tellurite reduction is not essential to confer tellurite resistance.199616535446
506160.7291A kiss of death--proteasome-mediated membrane fusion and programmed cell death in plant defense against bacterial infection. Eukaryotes have evolved various means for controlled and organized cellular destruction, known as programmed cell death (PCD). In plants, PCD is a crucial regulatory mechanism in multiple physiological processes, including terminal differentiation, senescence, and disease resistance. In this issue of Genes & Development, Hatsugai and colleagues (pp. 2496-2506) demonstrate a novel plant defense strategy to trigger bacteria-induced PCD, involving proteasome-dependent tonoplast and plasma membrane fusion followed by discharge of vacuolar antimicrobial and death-inducing contents into the apoplast.200919884251
531170.7289p-Aminobenzoic acid and chloramphenicol biosynthesis in Streptomyces venezuelae: gene sets for a key enzyme, 4-amino-4-deoxychorismate synthase. Amplification of sequences from Streptomyces venezuelae ISP5230 genomic DNA using PCR with primers based on conserved prokaryotic pabB sequences gave two main products. One matched pabAB, a locus previously identified in S. venezuelae. The second closely resembled the conserved pabB sequence consensus and hybridized with a 3.8 kb NcoI fragment of S. venezuelae ISP5230 genomic DNA. Cloning and sequence analysis of the 3.8 kb fragment detected three ORFs, and their deduced amino acid sequences were used in BLAST searches of the GenBank database. The ORF1 product was similar to PabB in other bacteria and to the PabB domain encoded by S. venezuelae pabAB. The ORF2 product resembled PabA of other bacteria. ORF3 was incomplete; its deduced partial amino acid sequence placed it in the MocR group of GntR-type transcriptional regulators. Introducing vectors containing the 3.8 kb NcoI fragment of S. venezuelae DNA into pabA and pabB mutants of Escherichia coli, or into the Streptomyces lividans pab mutant JG10, enhanced sulfanilamide resistance in the host strains. The increased resistance was attributed to expression of the pair of discrete translationally coupled p-aminobenzoic acid biosynthesis genes (designated pabB/pabA) cloned in the 3.8 kb fragment. These represent a second set of genes encoding 4-amino-4-deoxychorismate synthase in S. venezuelae ISP5230. In contrast to the fused pabAB set previously isolated from this species, they do not participate in chloramphenicol biosynthesis, but like pabAB they can be disrupted without affecting growth on minimal medium. The gene disruption results suggest that S. venezuelae may have a third set of genes encoding PABA synthase.200111495989
547180.7286Dual 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
527190.7283Characterization of the bagremycin biosynthetic gene cluster in Streptomyces sp. Tü 4128. Bagremycin A and bagremycin B isolated from Streptomyces sp. Tü 4128 have activities against Gram-positive bacteria, fungi and also have a weak antitumor activity, which make them have great potential for development of novel antibiotics. Here, we report a draft genome 8,424,112 bp in length of S. sp. Tü 4128 by Illumina Hiseq2000, and identify the bagremycins biosynthetic gene cluster (BGC) by bioinformatics analysis. The putative bagremycins BGC includes 16 open reading frames (ORFs) with the functions of biosynthesis, resistance and regulation. Disruptions of relative genes and HPLC analysis of bagremycins production demonstrated that not all the genes within the BGC are responsible for the biosynthesis of bagremycins. In addition, the biosynthetic pathways of bagremycins are proposed for deeper inquiries into their intriguing biosynthetic mechanism.201930526412