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614600.9808Arsenic resistance genes of As-resistant purple nonsulfur bacteria isolated from As-contaminated sites for bioremediation application. This study aimed to identify arsenic resistant mechanisms in As-resistant purple nonsulfur bacteria (PNSB) by screening them for presence of As-resistance genes and related enzymes. Resistance to As(III) and As(V) of four As-resistant PNSB determined in terms of median inhibition concentration (IC(50) values) were in the order of strains Rhodopseudomonas palustris C1 > R. palustris AB3 > Rubrivivax benzoatilyticus C31 > R. palustris L28 which corresponded to the presence of As-resistance genes in these bacteria. The strain C1 showed all As-marker genes; arsC, arsM, aioA, and acr3, while aioA was not detected in strain AB3. Strains C31 and L28 had only Arsenite-transporter gene, acr3. Translation of all these detected gene sequences of strain C1 to amino acid sequences showed that these proteins have vicinal cysteine; Cys126, Cys105, and Cys178 of Acr3, ArsC, AioA, respectively. Tertiary structure of proteins Acr3, ArsC, AioA, and ArsM showed strain C1 exhibits the high activities of arsenite oxidase and arsenate reductase enzymes that are encoded by aioA and arsC genes, respectively. Moreover, strain C1 with arsM gene produced volatile-methylated As-compounds; monomethylarsonic acid (MMA), dimethylarsenic acid (DMA), and arsenobetaine (AsB) in the presence of either As(III) or As(V). In conclusion, the strain C1 has great potential for its application in bioremediation of As-contaminated sites.201728054716
608710.9799Draft genome of Raoultella planticola, a high lead resistance bacterium from industrial wastewater. Isolation of heavy metals-resistant bacteria from their original habitat is a crucial step in bioremediation. Six lead (Pb) resistant bacterial strains were isolated and identified utilizing 16S rRNA to be Enterobacter ludwigii FACU 4, Shigella flexneri FACU, Microbacterium paraoxydans FACU, Klebsiella pneumoniae subsp. pneumonia FACU, Raoultella planticola FACU 3 and Staphylococcus xylosus FACU. It was determined that all these strains had their Minimum inhibitory concentration (MIC) to be 2500 ppm except R. planticola FACU 3 has a higher maximum tolerance concentration (MTC) up to 2700 ppm. We evaluated the survival of all six strains on lead stress, the efficiency of biosorption and lead uptake. It was found that R. planticola FACU 3 is the highest MTC and S. xylosus FACU was the lowest MTC in this evaluation. Therefore, transmission electron microscopy (TEM) confirmed the difference between the morphological responses of these two strains to lead stress. These findings led to explore more about the genome of R. planticola FACU 3 using illumine Miseq technology. Draft genome sequence analysis revealed the genome size of 5,648,460 bp and G + C content 55.8% and identified 5526 CDS, 75 tRNA and 4 rRNA. Sequencing technology facilitated the identification of about 47 genes related to resistance to many heavy metals including lead, arsenic, zinc, mercury, nickel, silver and chromium of R. planticola FACU 3 strain. Moreover, genome sequencing identified plant growth-promoting genes (PGPGs) including indole acetic acid (IAA) production, phosphate solubilization, phenazine production, trehalose metabolism and 4-hydroxybenzoate production genes and a lot of antibiotic-resistant genes.202336715862
608320.9798Bioactivity and genome analysis of Bacillus amyloliquefaciens GL18 isolated from the rhizosphere of Kobresia myosuroides in an alpine meadow. The unique eco-environment of the Qinghai-Tibet Plateau breeds abundant microbial resources. In this research, Bacillus amyloliquefaciens GL18, isolated from the rhizosphere of Kobresia myosuroides from an alpine meadow, and the antagonistic activity, bacteriostatic hydrolase activity, and low temperature, salt, and drought resistance of it were determined and analysed. The seedlings of Avena sativa were root-irrigated using bacteria suspensions (cell concentration 1 × 10(7) cfu/mL) of GL18, and the growth-promoting effect of GL18 on it was determined under cold, salt and drought stress, respectively. The whole genome of GL18 was sequenced, and its functional genes were analysed. GL18 presented significant antagonistic activity to Fusarium graminearum, Fusarium acuminatum, Fusarium oxysporum and Aspergillus niger (inhibition zone diameter > 17 mm). Transparent zones formed on four hydrolase detection media, indicating that GL18 secreted cellulase, protease, pectinase and β-1,3-glucanase. GL18 tolerated conditions of 10 °C, 11% NaCl and 15% PEG-6000, presenting cold, salt and drought resistance. GL18 improved the cold, salt and drought tolerance of A. sativa and it showed significant growth effects under different stress. The total length of the GL18 genome was 3,915,550 bp, and the number of coding DNA sequence was 3726. Compared with the clusters of orthologous groups of proteins, gene ontology and kyoto encyclopedia of genes and genomes databases, 3088, 2869 and 2357 functional genes were annotated, respectively. GL18 contained gene clusters related to antibacterial substances, functional genes related to the synthesis of plant growth-promoting substances, and encoding genes related to stress resistance. This study identified an excellent Bacillus strain and provided a theoretical basis for improving stress resistance and promoting the growth of herbages under abiotic stress.202438189906
522130.9797Molecular cloning of the DNA gyrase genes from Methylovorus sp. strain SS1 and the mechanism of intrinsic quinolone resistance in methylotrophic bacteria. The genes encoding the DNA gyrase A (GyrA) and B subunits (GyrB) of Methylovorus sp. strain SS1 were cloned and sequenced. gyrA and gyrB coded for proteins of 846 and 799 amino acids with calculated molecular weights of 94,328 and 88,714, respectively, and complemented Escherichia coli gyrA and gyrB temperature sensitive (ts) mutants. To analyze the role of type II topoisomerases in the intrinsic quinolone resistance of methylotrophic bacteria, the sequences of the quinolone resistance-determining regions (QRDRs) in the A subunit of DNA gyrase and the C subunit (ParC) of topoisomerase IV (Topo IV) of Methylovorus sp. strain SS1, Methylobacterium extorquens AM1 NCIB 9133, Methylobacillus sp, strain SK1 DSM 8269, and Methylophilus methylotrophus NCIB 10515 were determined. The deduced amino acid sequences of the QRDRs of the ParCs in the four methylotrophic bacteria were identical to that of E. coli ParC. The sequences of the QRDR in GyrA were also identical to those in E. coli GyrA except for the amino acids at positions 83, 87, or 95. The Ser83 to Thr substitution in Methylovorus sp. strain SS1, and the Ser83 to Leu and Asp87 to Asn substitutions in the three other methylotrophs, agreed well with the minimal inhibitory concentrations of quinolones in the four bacteria, suggesting that these residues play a role in the intrinsic susceptibility of methylotrophic bacteria to quinolones.200516404155
615440.9795Mechanism of arsenic resistance in endophytic bacteria isolated from endemic plant of mine tailings and their arsenophore production. Arsenic contamination is an important environmental problem around the world since its high toxicity, and bacteria resist to this element serve as valuable resource for its bioremediation. Aiming at searching the arsenic-resistant bacteria and determining their resistant mechanism, a total of 27 strains isolated from roots of Prosopis laevigata and Spharealcea angustifolia grown in a heavy metal-contaminated region in Mexico were investigated. The minimum inhibitory concentration (MIC) and transformation abilities of arsenate (As(5+)) and arsenite (As(3+)), arsenophore synthesis, arsenate uptake, and cytoplasmatic arsenate reductase (arsC), and arsenite transporter (arsB) genes were studied for these strains. Based on these results and the 16S rDNA sequence analysis, these isolates were identified as arsenic-resistant endophytic bacteria (AREB) belonging to the genera Arthrobacter, Bacillus, Brevibacterium, Kocuria, Microbacterium, Micrococcus, Pseudomonas, and Staphylococcus. They could tolerate high concentrations of arsenic with MIC from 20 to > 100 mM for As(5+) and 10-20 mM for As(3+). Eleven isolates presented dual abilities of As(5+) reduction and As(3+) oxidation. As the most effective strains, Micrococcus luteus NE2E1 reduced 94% of the As(5+) and Pseudomonas zhaodongensis NM2E7 oxidized 46% of As(3+) under aerobic condition. About 70 and 44% of the test strains produced arsenophores to chelate As(5+) and As(3+), respectively. The AREB may absorb arsenate via the same receptor of phosphate uptake or via other way in some case. The cytoplasmic arsenate reductase and alternative arsenate reduction pathways exist in these AREB. Therefore, these AREB could be candidates for the bioremediation process.201829476206
615850.9794Nitric oxide stress resistance in Porphyromonas gingivalis is mediated by a putative hydroxylamine reductase. Porphyromonas gingivalis, the causative agent of adult periodontitis, must maintain nitric oxide (NO) homeostasis and surmount nitric oxide stress from host immune responses or other oral bacteria to survive in the periodontal pocket. To determine the involvement of a putative hydroxylamine reductase (PG0893) and a putative nitrite reductase-related protein (PG2213) in P. gingivalis W83 NO stress resistance, genes encoding those proteins were inactivated by allelic exchange mutagenesis. The isogenic mutants P. gingivalis FLL455 (PG0893ermF) and FLL456 (PG2213ermF) were black pigmented and showed growth rates and gingipain and hemolytic activities similar to those of the wild-type strain. P. gingivalis FLL455 was more sensitive to NO than the wild type. Complementation of P. gingivalis FLL455 with the wild-type gene restored the level of NO sensitivity to a level similar to that of the parent strain. P. gingivalis FLL455 and FLL456 showed sensitivity to oxidative stress similar to that of the wild-type strain. DNA microarray analysis showed that PG0893 and PG2213 were upregulated 1.4- and 2-fold, respectively, in cells exposed to NO. In addition, 178 genes were upregulated and 201 genes downregulated more than 2-fold. The majority of these modulated genes were hypothetical or of unknown function. PG1181, predicted to encode a transcriptional regulator, was upregulated 76-fold. Transcriptome in silico analysis of the microarray data showed major metabolomic variations in key pathways. Collectively, these findings indicate that PG0893 and several other genes may play an important role in P. gingivalis NO stress resistance.201222247513
904660.9792Burkholderia pseudomallei resistance to antibiotics in biofilm-induced conditions is related to efflux pumps. Burkholderia pseudomallei, the causative agent of melioidosis, has been found to increase its resistance to antibiotics when growing as a biofilm. The resistance is related to several mechanisms. One of the possible mechanisms is the efflux pump. Using bioinformatics analysis, it was found that BPSL1661, BPSL1664 and BPSL1665 were orthologous genes of the efflux transporter encoding genes for biofilm-related antibiotic resistance, PA1874-PA1877 genes in Pseudomonas aeruginosa strain PAO1. Expression of selected encoding genes for the efflux transporter system during biofilm formation were investigated. Real-time reverse transcriptase PCR expression of amrB, cytoplasmic membrane protein of AmrAB-OprA efflux transporter encoding gene, was slightly increased, while BPSL1665 was significantly increased during growth of bacteria in biofilm formation. Minimum biofilm inhibition concentration and minimum biofilm eradication concentration (MBEC) of ceftazidime (CTZ), doxycycline (DOX) and imipenem were found to be 2- to 1024-times increased when compared to their MICs for of planktonic cells. Inhibition of the efflux transporter by adding phenylalanine arginine β-napthylamide (PAβN), a universal efflux inhibitor, decreased 2 to 16 times as much as MBEC in B. pseudomallei biofilms with CTZ and DOX. When the intracellular accumulation of antibiotics was tested to reveal the pump inhibition, only the concentrations of CTZ and DOX increased in PAβN treated biofilm. Taken together, these results indicated that BPSL1665, a putative precursor of the efflux pump gene, might be related to the adaptation of B. pseudomallei in biofilm conditions. Inhibition of efflux pumps may lead to a decrease of resistance to CTZ and DOX in biofilm cells.201627702426
637370.9791Antibiotic resistance and multidrug-resistant efflux pumps expression in lactic acid bacteria isolated from pozol, a nonalcoholic Mayan maize fermented beverage. Pozol is a handcrafted nonalcoholic Mayan beverage produced by the spontaneous fermentation of maize dough by lactic acid bacteria. Lactic acid bacteria (LAB) are carriers of chromosomal encoded multidrug-resistant efflux pumps genes that can be transferred to pathogens and/or confer resistance to compounds released during the fermentation process causing food spoiling. The aim of this study was to evaluate the antibiotic sensibility and the transcriptional expression of ABC-type efflux pumps in LAB isolated from pozol that contributes to multidrug resistance. Analysis of LAB and Staphylococcus (S.) aureus ATCC 29213 and ATCC 6538 control strains to antibiotic susceptibility, minimal inhibitory concentration (MIC), and minimal bactericidal concentration (MBC) to ethidium bromide were based in "standard methods" whereas the ethidium bromide efflux assay was done by fluorometric assay. Transcriptional expression of efflux pumps was analyzed by RT-PCR. LAB showed antibiotic multiresistance profiles, moreover, Lactococcus (L.) lactis and Lactobacillus (L.) plantarum displayed higher ethidium bromide efflux phenotype than S. aureus control strains. Ethidium bromide resistance and ethidium bromide efflux phenotypes were unrelated with the overexpression of lmrD in L. lactics, or the underexpression of lmrA in L. plantarum and norA in S. aureus. These findings suggest that, moreover, the analyzed efflux pumps genes, other unknown redundant mechanisms may underlie the antibiotic resistance and the ethidium bromide efflux phenotype in L. lactis and L. plantarum. Phenotypic and molecular drug multiresistance assessment in LAB may improve a better selection of the fermentation starter cultures used in pozol, and to control the antibiotic resistance widespread and food spoiling for health safety.201627247772
873780.9791Role of Biosynthetic Gene Cluster BGC3 in the Cariogenic Virulence of Streptococcus mutans. OBJECTIVE: To investigate the role of the biosynthetic gene cluster BGC3 of Streptococcus mutans (S. mutans) in the process of dental caries. METHODS: BGC3 and ∆BGC3 S. mutans strains were constructed and their growth curves were evaluated. Acid production capacity was assessed by evaluating pH reduction levels over identical culture periods. The survival of bacteria in phosphate citrate buffer solution (pH 3.0) was quantified. The expression levels of virulence genes (atpF, gtfC, gtfD, spaP, vicR and ftf) were analysed using the qPCR. Co-culture experiments were conducted to evaluate bacterial adaptability. Bacterial viability was determined by microscopical examination of live/dead staining. RESULTS: Deletion of BGC3 did not significantly impact S. mutans growth or acid production in biofilms. The ∆BGC3 strain exhibited enhanced acid resistance and higher expression levels of virulence genes compared to the wild type. In addition, ∆BGC3 exhibited superior bacterial viability in the co-culture system. CONCLUSION: BGC3 affected the acid resistance and expression of caries-related genes in S. mutans. The BGC3 knockout strain exhibited a more robust survival capability than the wild-type strain.202540162656
635290.9789Cloning and characterization of grpE in Acetobacter pasteurianus NBRC 3283. The grpE gene in Acetobacter pasteurianus NBRC 3283 was cloned and characterized, to elucidate the mechanism underlying the resistance of acetic acid bacteria to the stressors existing during acetic acid fermentation. This gene was found to be located in tandem with two related genes, appearing on the genome in the order grpE-dnaK-dnaJ. A sigma(32)-type promoter sequence was found in the upstream region of grpE. The relative transcription levels of grpE, dnaK, and dnaJ mRNA were in the ratio of approximately 1:2:0.1, and the genes were transcribed as grpE-dnaK, dnaK, and dnaJ. The transcription level of grpE was elevated by heat shock and treatment with ethanol. Co-overexpression of GrpE with DnaK/J in cells resulted in improved growth compared to the single overexpression of DnaK/J in high temperature or ethanol-containing conditions, suggesting that GrpE acts cooperatively with DnaK/J for expressing resistance to those stressors considered to exist during acetic acid fermentation. Our findings indicate that GrpE is closely associated with adaptation to stressors in A. pasteurianus and may play an important role in acetic acid fermentation.201020129077
404100.9789Plasmid-borne cadmium resistance genes in Listeria monocytogenes are similar to cadA and cadC of Staphylococcus aureus and are induced by cadmium. pLm74 is the smallest known plasmid in Listeria monocytogenes. It confers resistance to the toxic divalent cation cadmium. It contains a 3.1-kb EcoRI fragment which hybridizes with the cadAC genes of plasmid pI258 of Staphylococcus aureus. When introduced into cadmium-sensitive L. monocytogenes or Bacillus subtilis strains, this fragment conferred cadmium resistance. The DNA sequence of the 3.1-kb EcoRI fragment contains two open reading frames, cadA and cadC. The deduced amino acid sequences are similar to those of the cad operon of plasmid pI258 of S. aureus, known to prevent accumulation of Cd2+ in the bacteria by an ATPase efflux mechanism. The cadmium resistance determinant of L. monocytogenes does not confer zinc resistance, in contrast to the cadAC determinant of S. aureus, suggesting that the two resistance mechanisms are slightly different. Slot blot DNA-RNA hybridization analysis showed cadmium-inducible synthesis of L. monocytogenes cadAC RNA.19948188605
662110.9789Gene expression and physiological role of Pseudomonas aeruginosa methionine sulfoxide reductases during oxidative stress. Pseudomonas aeruginosa PAO1 has two differentially expressed methionine sulfoxide reductase genes: msrA (PA5018) and msrB (PA2827). The msrA gene is expressed constitutively at a high level throughout all growth phases, whereas msrB expression is highly induced by oxidative stress, such as sodium hypochlorite (NaOCl) treatment. Inactivation of either msrA or msrB or both genes (msrA msrB mutant) rendered the mutants less resistant than the parental PAO1 strain to oxidants such as NaOCl and H2O2. Unexpectedly, msr mutants have disparate resistance patterns when exposed to paraquat, a superoxide generator. The msrA mutant had a higher paraquat resistance level than the msrB mutant, which had a lower paraquat resistance level than the PAO1 strain. The expression levels of msrA showed an inverse correlation with the paraquat resistance level, and this atypical paraquat resistance pattern was not observed with msrB. Virulence testing using a Drosophila melanogaster model revealed that the msrA, msrB, and, to a greater extent, msrA msrB double mutants had an attenuated virulence phenotype. The data indicate that msrA and msrB are essential genes for oxidative stress protection and bacterial virulence. The pattern of expression and mutant phenotypes of P. aeruginosa msrA and msrB differ from previously characterized msr genes from other bacteria. Thus, as highly conserved genes, the msrA and msrB have diverse expression patterns and physiological roles that depend on the environmental niche where the bacteria thrive.201323687271
363120.9788Constitutive arsenite oxidase expression detected in arsenic-hypertolerant Pseudomonas xanthomarina S11. Pseudomonas xanthomarina S11 is an arsenite-oxidizing bacterium isolated from an arsenic-contaminated former gold mine in Salsigne, France. This bacterium showed high resistance to arsenite and was able to oxidize arsenite to arsenate at concentrations up to 42.72 mM As[III]. The genome of this strain was sequenced and revealed the presence of three ars clusters. One of them is located on a plasmid and is organized as an "arsenic island" harbouring an aio operon and genes involved in phosphorous metabolism, in addition to the ars genes. Neither the aioXRS genes nor a specific sigma-54-dependent promoter located upstream of aioBA genes, both involved in regulation of arsenite oxidase expression in other arsenite-oxidizing bacteria, could be identified in the genome. This observation is in accordance with the fact that no difference was observed in expression of arsenite oxidase in P. xanthomarina S11, whether or not the strain was grown in the presence of As[III].201525753102
6190130.9787Identifying Escherichia coli genes involved in intrinsic multidrug resistance. Multidrug resistance is a major cause of clinical failure in treating bacterial infections. Increasing evidence suggests that bacteria can resist multiple antibiotics through intrinsic mechanisms that rely on gene products such as efflux pumps that expel antibiotics and special membrane proteins that block the penetration of drug molecules. In this study, Escherichia coli was used as a model system to explore the genetic basis of intrinsic multidrug resistance. A random mutant library was constructed in E. coli EC100 using transposon mutagenesis. The library was screened by growth measurement to identify the mutants with enhanced or reduced resistance to chloramphenicol (Cm). Out of the 4,000 mutants screened, six mutants were found to be more sensitive to Cm and seven were more resistant compared to the wild-type EC100. Mutations in 12 out of the 13 mutants were identified by inverse polymerase chain reaction. Mutants of the genes rob, garP, bipA, insK, and yhhX were more sensitive to Cm compared to the wild-type EC100, while the mutation of rhaB, yejM, dsdX, nagA, yccE, atpF, or htrB led to higher resistance. Overexpression of rob was found to increase the resistance of E. coli biofilms to tobramycin (Tob) by 2.7-fold, while overexpression of nagA, rhaB, and yccE significantly enhanced the susceptibility of biofilms by 2.2-, 2.5-, and 2.1-fold respectively.200818807027
328140.9787Multiresistance 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
3615150.9787Insights to antimicrobial resistance: heavy metals can inhibit antibiotic resistance in bacteria isolated from wastewater. The alarming upsurge in the co-existence of heavy metal and antibiotic resistance may have a devastating impact on humans, animals, and the environment. Four metal-resistant bacteria were isolated from hospital effluents and industrial drain. Heavy metal resistance and antimicrobial resistance were examined in the isolates followed by identification through 16S rRNA gene sequencing. Delftia tsuruhatensis strain FK-01 and Carnobacterium inhibens strain FK-02 tolerated arsenic with maximal tolerated concentration (MTC) of 30 mM and 10 mM, respectively. Staphylococcus hominis strain FK-04 tolerated copper up to 4 mM and lead-resistant Raoultella ornithinolytica strain FK-05 exhibited tolerance to 1 mM lead. The growth kinetics of bacteria were monitored in the presence of metals and the following antibiotics, tetracycline, chloramphenicol, and kanamycin. The presence of arsenate significantly enhanced tetracycline resistance in C. inhibens. Heavy metal-induced antibiotic resistance was also observed in S. hominis and R. ornithinolytica, against chloramphenicol and tetracycline respectively. D. tsuruhatensis showed resistance to kanamycin but when grown in the presence of arsenic and kanamycin, bacteria lost resistance to the antibiotic. Therefore, it is suggested that the novel arsenate-resistant strain Delftia tsuruhatensis FK-01 has a unique ability to inhibit antimicrobial resistance that can be harnessed in bioremediation.202235254524
8797160.9785Presence of quorum-sensing systems associated with multidrug resistance and biofilm formation in Bacteroides fragilis. Bacteroides fragilis constitutes 1-2% of the natural microbiota of the human digestive tract and is the predominant anaerobic opportunistic pathogen in gastrointestinal infections. Most bacteria use quorum sensing (QS) to monitor cell density in relation to other cells and their environment. In Gram-negative bacteria, the LuxRI system is common. The luxR gene encodes a transcriptional activator inducible by type I acyl-homoserine lactone autoinducers (e.g., N-[3-oxohexanoyl] homoserine lactone and hexanoyl homoserine lactone [C6-HSL]). This study investigated the presence of QS system(s) in B. fragilis. The genome of American-type culture collection strain no. ATCC25285 was searched for QS genes. The strain was grown to late exponential phase in the presence or absence of synthetic C6-HSL and C8-HSL or natural homoserine lactones from cell-free supernatants from spent growth cultures of other bacteria. Growth, susceptibility to antimicrobial agents, efflux pump gene (bmeB) expression, and biofilm formation were measured. Nine luxR and no luxI orthologues were found. C6-HSL and supernatants from Yersinia enterocolitica, Vibrio cholerae, and Pseudomonas aeruginosa caused a significant (1) reduction in cellular density and (2) increases in expression of four putative luxR genes, bmeB3, bmeB6, bmeB7, and bmeB10, resistance to various antibiotics, which was reduced by carbonyl cyanide-m-chlorophenyl hydrazone (CCCP, an uncoupler that dissipates the transmembrane proton gradient, which is also the driving force of resistance nodulation division efflux pumps) and (3) increase in biofilm formation. Susceptibility of ATCC25285 to C6-HSL was also reduced by CCCP. These data suggest that (1) B. fragilis contains putative luxR orthologues, which could respond to exogenous homoserine lactones and modulate biofilm formation, bmeB efflux pump expression, and susceptibility to antibiotics, and (2) BmeB efflux pumps could transport homoserine lactones.200818188535
139170.9785The strategy of arsenic metabolism in an arsenic-resistant bacterium Stenotrophomonas maltophilia SCSIOOM isolated from fish gut. Bacteria are candidates for the biotransformation of environmental arsenic (As), while As metabolism in bacteria is not yet fully understood. In this study, we sequenced the genome of an As-resistant bacterium strain Stenotrophomonas maltophilia SCSIOOM isolated from the fish gut. After arsenate (As(V)) exposure, S. maltophilia transformed As(V) to organoarsenicals, along with the significant change of the expression of 40 genes, including the upregulation of arsH, arsRBC and betIBA. The heterogeneous expression of arsH and arsRBC increased As resistance of E. coli AW3110 by increasing As efflux and transformation. E. coli AW3110 (pET-betIBA) could transform inorganic As into dimethylarsinate (DMA) and nontoxic arsenobetaine (AsB), which suggested that AsB could be synthesized through the synthetic pathway of its analog-glycine betaine. In addition, the existence of arsRBC, betIBA and arsH reduced the reactive oxygen species (ROS) induced by As exposure. In total, these results demonstrated that S. maltophilia adopted an As metabolism strategy by reducing As accumulation and synthesizing less toxic As species. We first reported the production and potential synthetic pathway of AsB in bacteria, which improved our knowledge of As toxicology in microorganisms.202236058313
6085180.9785Heavy metal resistance and genotypic analysis of metal resistance genes in gram-positive and gram-negative bacteria present in Ni-rich serpentine soil and in the rhizosphere of Alyssum murale. Forty-six bacterial cultures, including one culture collection strain, thirty from the rhizosphere of Alyssum murale and fifteen from Ni-rich soil, were tested for their ability to tolerate arsenate, cadmium, chromium, zinc, mercury, lead, cobalt, copper, and nickel in their growth medium. The resistance patterns, expressed as minimum inhibitory concentrations, for all cultures to the nine different metal ions were surveyed by using the agar dilution method. A large number of the cultures were resistant to Ni (100%), Pb (100%), Zn (100%), Cu (98%), and Co (93%). However, 82, 71, 58 and 47% were sensitive to As, Hg, Cd and Cr(VI), respectively. All cultures had multiple metal-resistant, with heptametal resistance as the major pattern (28.8%). Five of the cultures (about of 11.2% of the total), specifically Arthrobacter rhombi AY509239, Clavibacter xyli AY509235, Microbacterium arabinogalactanolyticum AY509226, Rhizobium mongolense AY509209 and Variovorax paradoxus AY512828 were tolerant to nine different metals. The polymerase chain reaction in combination with DNA sequence analysis was used to investigate the genetic mechanism responsible for the metal resistance in some of these gram-positive and gram-negative bacteria that were, highly resistant to Hg, Zn, Cr and Ni. The czc, chr, ncc and mer genes that are responsible for resistance to Zn, Cr, Ni and Hg, respectively, were shown to be present in these bacteria by using PCR. In the case of, M. arabinogalactanolyticum AY509226 these genes were shown to have high homology to the czcD, chrB, nccA, and mer genes of Ralstonia metallidurans CH34. Therefore, Hg, Zn, Cr and Ni resistance genes are widely distributed in both gram-positive and gram-negative isolates obtained from A. murale rhizosphere and Ni-rich soils.200717276484
6189190.9784Characterization of all RND-type multidrug efflux transporters in Vibrio parahaemolyticus. Resistance nodulation cell division (RND)-type efflux transporters play the main role in intrinsic resistance to various antimicrobial agents in many gram-negative bacteria. Here, we estimated 12 RND-type efflux transporter genes in Vibrio parahaemolyticus. Because VmeAB has already been characterized, we cloned the other 11 RND-type efflux transporter genes and characterized them in Escherichia coli KAM33 cells, a drug hypersusceptible strain. KAM33 expressing either VmeCD, VmeEF, or VmeYZ showed increased minimum inhibitory concentrations (MICs) for several antimicrobial agents. Additional four RND-type transporters were functional as efflux pumps only when co-expressed with VpoC, an outer membrane component in V. parahaemolyticus. Furthermore, VmeCD, VmeEF, and VmeYZ co-expressed with VpoC exhibited a broader substrate specificity and conferred higher resistance than that with TolC of E. coli. Deletion mutants of these transporter genes were constructed in V. parahaemolyticus. TM32 (ΔvmeAB and ΔvmeCD) had significantly decreased MICs for many antimicrobial agents and the number of viable cells after exposure to deoxycholate were markedly reduced. Strains in which 12 operons were all disrupted had very low MICs and much lower fluid accumulation in rabbit ileal loops. These results indicate that resistance nodulation cell division-type efflux transporters contribute not only to intrinsic resistance but also to exerting the virulence of V. parahaemolyticus.201323894076