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52800.6913Effect 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
50710.6422Tellurite 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
10220.6389Paradoxical 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
33730.6375Effect of nifA product on suppression of Nif- phenotype of gln mutation and constitutive synthesis of nitrogenase in Klebsiella pneumoniae. This paper describes the role of nifA product on the ammonia regulation of nitrogen fixation in K. pneumoniae. A plasmid carrying nifA gene under the promoter of tetracycline resistance gene was constructed. When this nifA carrying plasmid was introduced into a glnAG mutant, the Nif- phenotype of this gln mutant was suppressed. Furthermore, when the plasmid was introduced into the wild type and glnAG mutant, derepression of nitrogenase synthesis in ammonia occurred in both strains and the products of nif genes can be detected by two-dimensional gel electrophoresis in the extracts of these ammonia-grown bacterial cells. The constitutive synthesis of nitrogenase in NH4+ was also demonstrated in free living nitrogen-fixing bacteria, Enterobacter cloacae, when the bacteria received the plasmid carrying nifA gene from K. pneumoniae.19836143398
53040.6350Location 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
34450.6349Identification 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
55560.6332Mutations 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
57670.6325Caenorhabditis 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
600680.6325Missense Mutations in the CrrB Protein Mediate Odilorhabdin Derivative Resistance in Klebsiella pneumoniae. NOSO-502 is a preclinical antibiotic candidate of the Odilorhabdin class. This compound exhibits activity against Enterobacteriaceae pathogens, including carbapenemase-producing bacteria and most of the Colistin (CST)-resistant strains. Among a collection of CST-resistant Klebsiella pneumoniae strains harboring mutations on genes pmrAB, mgrB, phoPQ, and crrB, only those bearing mutations in gene crrB were found to be resistant to NOSO-502.CrrB is a histidine kinase which acts with the response regulator CrrA to modulate the PmrAB system, which finally induces the restructuring of the lipopolysaccharide present on the outer membrane and thus leading to CST resistance. Moreover, crrB mutations also enhance the transcription of neighboring genes such as H239_3063, an ABC transporter transmembrane region; H239_3064, a putative efflux pump also known as KexD; and H239_3065, a N-acetyltransferase.To elucidate the mechanism of resistance to NOSO-502 induced by CrrB missense mutations in K. pneumoniae, mutants of NCTC 13442 and ATCC BAA-2146 strains resistant to NOSO-502 and CST with single amino acid substitutions in CrrB (S8N, F33Y, Y34N, W140R, N141I, P151A, P151L, P151S, P151T, F303Y) were selected. Full susceptibility to NOSO-502 was restored in crrA or crrB deleted K. pneumoniae NCTC 13442 CrrB(P151L) mutants, confirming the role of CrrAB in controlling this resistance pathway. Deletion of kexD (but no other neighboring genes) in the same mutant also restored NOSO-502-susceptibility. Upregulation of the kexD gene expression was observed for all CrrB mutants. Finally, plasmid expression of kexD in a K. pneumoniae strain missing the locus crrABC and kexD significantly increased resistance to NOSO-502.202333685902
53290.6310Three new dominant drug resistance cassettes for gene disruption in Saccharomyces cerevisiae. Disruption-deletion cassettes are powerful tools used to study gene function in many organisms, including Saccharomyces cerevisiae. Perhaps the most widely useful of these are the heterologous dominant drug resistance cassettes, which use antibiotic resistance genes from bacteria and fungi as selectable markers. We have created three new dominant drug resistance cassettes by replacing the kanamycin resistance (kan(r)) open reading frame from the kanMX3 and kanMX4 disruption-deletion cassettes (Wach et al., 1994) with open reading frames conferring resistance to the antibiotics hygromycin B (hph), nourseothricin (nat) and bialaphos (pat). The new cassettes, pAG25 (natMX4), pAG29 (patMX4), pAG31 (patMX3), pAG32 (hphMX4), pAG34 (hphMX3) and pAG35 (natMX3), are cloned into pFA6, and so are in all other respects identical to pFA6-kanMX3 and pFA6-kanMX4. Most tools and techniques used with the kanMX plasmids can also be used with the hph, nat and patMX containing plasmids. These new heterologous dominant drug resistance cassettes have unique antibiotic resistance phenotypes and do not affect growth when inserted into the ho locus. These attributes make the cassettes ideally suited for creating S. cerevisiae strains with multiple mutations within a single strain.199910514571
527100.6309Characterization 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
531110.6309p-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
806120.6305A two-component small multidrug resistance pump functions as a metabolic valve during nicotine catabolism by Arthrobacter nicotinovorans. The genes nepAB of a small multidrug resistance (SMR) pump were identified as part of the pAO1-encoded nicotine regulon responsible for nicotine catabolism in Arthrobacter nicotinovorans. When [(14)C]nicotine was added to the growth medium the bacteria exported the (14)C-labelled end product of nicotine catabolism, methylamine. In the presence of the proton-motive force inhibitors 2,4-dinitrophenol (DNP), carbonyl cyanide m-chlorophenylhydrazone (CCCP) or the proton ionophore nigericin, export of methylamine was inhibited and radioactivity accumulated inside the bacteria. Efflux of [(14)C]nicotine-derived radioactivity from bacteria was also inhibited in a pmfR : cmx strain with downregulated nepAB expression. Because of low amine oxidase levels in the pmfR : cmx strain, gamma-N-methylaminobutyrate, the methylamine precursor, accumulated. Complementation of this strain with the nepAB genes, carried on a plasmid, restored the efflux of nicotine breakdown products. Both NepA and NepB were required for full export activity, indicating that they form a two-component efflux pump. NepAB may function as a metabolic valve by exporting methylamine, the end product of nicotine catabolism, and, in conditions under which it accumulates, the intermediate gamma-N-methylaminobutyrate.200717464069
803130.6300Nucleotide sequences and genetic analysis of hydrogen oxidation (hox) genes in Azotobacter vinelandii. Azotobacter vinelandii contains a heterodimeric, membrane-bound [NiFe]hydrogenase capable of catalyzing the reversible oxidation of H2. The beta and alpha subunits of the enzyme are encoded by the structural genes hoxK and hoxG, respectively, which appear to form part of an operon that contains at least one further potential gene (open reading frame 3 [ORF3]). In this study, determination of the nucleotide sequence of a region of 2,344 bp downstream of ORF3 revealed four additional closely spaced or overlapping ORFs. These ORFs, ORF4 through ORF7, potentially encode polypeptides with predicted masses of 22.8, 11.4, 16.3, and 31 kDa, respectively. Mutagenesis of the chromosome of A. vinelandii in the area sequenced was carried out by introduction of antibiotic resistance gene cassettes. Disruption of hoxK and hoxG by a kanamycin resistance gene abolished whole-cell hydrogenase activity coupled to O2 and led to loss of the hydrogenase alpha subunit. Insertional mutagenesis of ORF3 through ORF7 with a promoterless lacZ-Kmr cassette established that the region is transcriptionally active and involved in H2 oxidation. We propose to call ORF3 through ORF7 hoxZ, hoxM, hoxL, hoxO, and hoxQ, respectively. The predicted hox gene products resemble those encoded by genes from hydrogenase-related operons in other bacteria, including Escherichia coli and Alcaligenes eutrophus.19921624446
6090140.6299Draft genome sequence of Mesorhizobium alhagi CCNWXJ12-2T, a novel salt-resistant species isolated from the desert of northwestern China. Mesorhizobium alhagi strain CCNWXJ12-2(T) is a novel species of soil-dwelling, nitrogen-fixing bacteria that can form symbiotic root nodules with Alhagi sparsifolia. Moreover, the strain has high resistance to salt and alkali. Here we report the draft genome sequence of Mesorhizobium alhagi strain CCNWXJ12-2(T). A large number of osmotic regulation-related genes have been identified.201222328758
812150.6296Characterization of plQ5 plasmid originating fromKlebsiella pneumoniae. plQ5 plasmid consists of a group of genes specifying resistance to ampicillin, chloramphenicol, carbencillin, kanamycin and trimethoprim-sulphamethoxazole. It is isolated inKlebslella pneumoniae ZD532, is about 26.8 Kb and is freely transmissible to various bacterial species of Gram-negative bacteria. Physical characterization revealed that plQ5 plasmid has a single site forHindill,BamHI,EcoRI and two sites forBglII restriction enzyme.199024429982
8717160.6292Protective Effect of Pediococcus pentosaceus Li05 on Constipation via TGR5/TPH1/5-HT Activation. Pediococcus pentosaceus Li05, a strain of lactic acid bacteria isolated from the faeces of healthy volunteers, exhibited potential protective effects against various diseases. This study performed third-generation sequencing and detailed characterisation of its genome. The Li05 chromosome harboured conserved genes associated with acid resistance (atp), bile salt resistance (bsh), oxidative stress resistance (hsl, dltA, and et al.), and adhesion (nrd, gap, and et al.), whereas the plasmid did not contain antibiotic resistance or virulence genes. Following intervention with Li05 in loperamide-induced constipated mice, constipation symptoms improved. Meanwhile, alterations in gut microbiota, increased BSH activity in faeces, and modifications to the faecal bile acid profile were observed. Additionally, expression levels of TGR5 and TPH1 in the colon of the mice increased, leading to elevated 5-HT levels. When the TGR5 gene was knocked out or the TPH1 inhibitor LX1606 was administered to suppress 5-HT synthesis in constipated mice, the beneficial effects of Li05 on gastrointestinal motility and mucus secretion were reversed. Culturing intestinal organoids demonstrated that increased bile acids such as DCA, Iso-LCA, and EALCA could enhance 5-HT levels through the TGR5/TPH1 axis. Therefore, we concluded that Li05 regulated bile acid metabolism, subsequently increasing 5-HT levels through the TGR5/TPH1 axis, thus alleviating constipation.202541159760
101170.6291The encapsulated strain TIGR4 of Streptococcus pneumoniae is phagocytosed but is resistant to intracellular killing by mouse microglia. The polysaccharide capsule is a major virulence factor of Streptococcus pneumoniae as it confers resistance to phagocytosis. The encapsulated serotype 4 TIGR4 strain was shown to be efficiently phagocytosed by the mouse microglial cell line BV2, whereas the type 3 HB565 strain resisted phagocytosis. Comparing survival after uptake of TIGR4 or its unencapsulated derivative FP23 in gentamicin protection and phagolysosome maturation assays, it was shown that TIGR4 was protected from intracellular killing. Pneumococcal capsular genes were up-regulated in intracellular TIGR4 bacteria recovered from microglial cells. Actual presence of bacteria inside BV2 cells was confirmed by transmission electron microscopy (TEM) for both TIGR4 and FP23 strains, but typical phagosomes/phagolysosomes were detected only in cells infected with the unencapsulated strain. In a mouse model of meningitis based on intracranic inoculation of pneumococci, TIGR4 caused lethal meningitis with an LD(50) of 2 × 10² CFU, whereas the LD(50) for the unencapsulated FP23 was greater than 10⁷ CFU. Phagocytosis of TIGR4 by microglia was also demonstrated by TEM and immunohistochemistry on brain samples from infected mice. The results indicate that encapsulation does not protect the TIGR4 strain from phagocytosis by microglia, while it affords resistance to intracellular killing.201020615478
347180.6287A novel plasmid gene involved in bacteriophage PRD1 infection and conjugative host-range. PRD1 infects bacteria carrying IncN plasmids by binding to their conjugative pili. Mutations in a plasmid locus kikA close to the pilus region result in PRD1 resistance and reduced conjugation proficiency to Klebsiella but not to Escherichia coli. One of the two genes of kikA is sufficient to restore both normal phenotypes. PRD1 binds to cells carrying the mutant plasmid but fails to inject its genome.19968812786
529190.6281Crystal 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