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605400.9486Lactobacillus Strains for Vegetable Juice Fermentation-Quality and Health Aspects. Vegetable juices are new carrier variants for beneficial bacteria, representing an alternative to dairy-fermented products, especially for vegan, strict vegetarian, or allergic consumers. The aim of this study was to characterize several Romanian native lactic acid bacteria (LAB) strains to select valuable nutritional and probiotic strains for vegetable juice fermentation. Nineteen LAB strains were analyzed for antibiotic susceptibility (disc-diffusion method), the presence of antibiotic resistance genes, the presence of functional genes. and the production of organic acids by HPLC. Antibiotic resistant strains were observed only with ampicillin (Amp10) and kanamycin (K30), 79% and 32%, respectively, with results partially confirmed by molecular analysis. Multiplex PCR revealed the presence of LBA1272, dltD, folP, agl, α-amy, malL, and ribA genes, related to stress resistance, starch metabolism, and production of vitamins, except for folK. HPLC analyses were performed on beet roots (SF), tomato (TM), and a mixture of carrots, celery, and beet (MTS) juices. High values of lactic acid were recorded in all cases of LAB fermentation (5034-14,176 µg/mL). The maximum values recorded for acetic acid did not exceed 2.5 mg/mL having a positive influence on the product's taste.202236359394
613210.9437Molecular characterization of copper resistance genes from Xanthomonas citri subsp. citri and Xanthomonas alfalfae subsp. citrumelonis. Copper sprays have been widely used for control of endemic citrus canker caused by Xanthomonas citri subsp. citri in citrus-growing areas for more than 2 decades. Xanthomonas alfalfae subsp. citrumelonis populations were also exposed to frequent sprays of copper for several years as a protective measure against citrus bacterial spot (CBS) in Florida citrus nurseries. Long-term use of these bactericides has led to the development of copper-resistant (Cu(r)) strains in both X. citri subsp. citri and X. alfalfae subsp. citrumelonis, resulting in a reduction of disease control. The objectives of this study were to characterize for the first time the genetics of copper resistance in X. citri subsp. citri and X. alfalfae subsp. citrumelonis and to compare these organisms to other Cu(r) bacteria. Copper resistance determinants from X. citri subsp. citri strain A44(pXccCu2) from Argentina and X. alfalfae subsp. citrumelonis strain 1381(pXacCu2) from Florida were cloned and sequenced. Open reading frames (ORFs) related to the genes copL, copA, copB, copM, copG, copC, copD, and copF were identified in X. citri subsp. citri A44. The same ORFs, except copC and copD, were also present in X. alfalfae subsp. citrumelonis 1381. Transposon mutagenesis of the cloned copper resistance determinants in pXccCu2 revealed that copper resistance in X. citri subsp. citri strain A44 is mostly due to copL, copA, and copB, which are the genes in the cloned cluster with the highest nucleotide homology (≥ 92%) among different Cu(r) bacteria.201121515725
54020.9435Effect 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
611630.9433Identification of plasmid encoded osmoregulatory genes from halophilic bacteria isolated from the rhizosphere of halophytes. Bacterial plasmids carry genes that code for additional traits such as osmoregulation, CO(2) fixation, antibiotic and heavy metal resistance, root nodulation and nitrogen fixation. The main objective of the current study was to identify plasmid-conferring osmoregulatory genes in bacteria isolated from rhizospheric and non-rhizospheric soils of halophytes (Salsola stocksii and Atriplex amnicola). More than 55% of halophilic bacteria from the rhizosphere and 70% from non-rhizospheric soils were able to grow at 3 M salt concentrations. All the strains showed optimum growth at 1.5-3.0 M NaCl. Bacterial strains from the Salsola rhizosphere showed maximum (31%) plasmid elimination during curing experiments as compared to bacterial strains from the Atriplex rhizosphere and non-rhizospheric soils. Two plasmid cured strains Bacillus HL2HP6 and Oceanobacillus HL2RP7 lost their ability to grow in halophilic medium, but they grew well on LB medium. The plasmid cured strains also showed a change in sensitivity to specific antibiotics. These plasmids were isolated and transformed into E. coli strains and growth response of wild-type and transformed E. coli strains was compared at 1.5-4 M NaCl concentrations. Chromosomal DNA and plasmids from Bacillus filamentosus HL2HP6 were sequenced by using high throughput sequencing approach. Results of functional analysis of plasmid sequences showed different proteins and enzymes involved in osmoregulation of bacteria, such as trehalose, ectoine synthetase, porins, proline, alanine, inorganic ion transporters, dehydrogenases and peptidases. Our results suggested that plasmid conferring osmoregulatory genes play a vital role to maintain internal osmotic balance of bacterial cells and these genes can be used to develop salt tolerant transgenic crops.201931422229
872140.9419Chromium metabolism characteristics of coexpression of ChrA and ChrT gene. OBJECTIVE: Serratia sp. S2 is a wild strain with chromium resistance and reduction ability. Chromium(VI) metabolic-protein-coding gene ChrA and ChrT were cloned from Serratia sp. S2, and ligated with prokaryotic expression vectors pET-28a (+) and transformed into E. coli BL21 to construct ChrA, ChrT and ChrAT engineered bacteria. By studying the characteristics of Cr(VI) metabolism in engineered bacteria, the function and mechanism of the sole expression and coexpression of ChrA and ChrT genes were studied. METHODS: Using Serratia sp. S2 genome as template, ChrA and ChrT genes were amplified by PCR, and prokaryotic expression vectors was ligated to form the recombinant plasmid pET-28a (+)-ChrA, pET-28a (+)-ChrT and pET-28a (+)-ChrAT, and transformed into E. coli BL21 to construct ChrA, ChrT, ChrAT engineered bacteria. The growth curve, tolerance, and reduction of Cr(VI), the distribution of intracellular and extracellular Cr, activity of chromium reductase and intracellular oxidative stress in engineered bacteria were measured to explore the metabolic characteristics of Cr(VI) in ChrA, ChrT, ChrAT engineered bacteria. RESULTS: ChrA, ChrT and ChrAT engineered bacteria were successfully constructed by gene recombination technology. The tolerance to Cr(VI) was Serratia sp. S2 > ChrAT ≈ ChrA > ChrT > Control (P < 0.05), and the reduction ability to Cr(VI) was Serratia sp. S2 > ChrAT ≈ ChrT > ChrA (P < 0.05). The chromium distribution experiments confirmed that Cr(VI) and Cr(III) were the main valence states. Effect of electron donors on chromium reductase activity was NADPH > NADH > non-NAD(P)H (P < 0.05). The activity of chromium reductase increased significantly with NAD(P)H (P < 0.05). The Glutathione and NPSH (Non-protein Sulfhydryl) levels of ChrA, ChrAT engineered bacteria increased significantly (P < 0.05) under the condition of Cr(VI), but there was no significant difference in the indexes of ChrT engineered bacteria (P > 0.05). CONCLUSION: ChrAT engineered bacteria possesses resistance and reduction abilities of Cr(VI). ChrA protein endows the strain with the ability to resist Cr(VI). ChrT protein reduces Cr(VI) to Cr(III) by using NAD(P)H as electronic donor. The reduction process promotes the production of GSH, GSSG and NPSH to maintain the intracellular reduction state, which further improves the Cr(VI) tolerance and reduction ability of ChrAT engineered bacteria.202032768747
872850.9419Identification of the defense-related gene VdWRKY53 from the wild grapevine Vitis davidii using RNA sequencing and ectopic expression analysis in Arabidopsis. BACKGROUND: Grapevine is an important fruit crop grown worldwide, and its cultivars are mostly derived from the European species Vitis vinifera, which has genes for high fruit quality and adaptation to a wide variety of climatic conditions. Disease resistance varies substantially across grapevine species; however, the molecular mechanisms underlying such variation remain uncharacterized. RESULTS: The anatomical structure and disease symptoms of grapevine leaves were analyzed for two grapevine species, and the critical period of resistance of grapevine to pathogenic bacteria was determined to be 12 h post inoculation (hpi). Differentially expressed genes (DEGs) were identified from transcriptome analysis of leaf samples obtained at 12 and 36 hpi, and the transcripts in four pathways (cell wall genes, LRR receptor-like genes, WRKY genes, and pathogenesis-related (PR) genes) were classified into four co-expression groups by using weighted correlation network analysis (WGCNA). The gene VdWRKY53, showing the highest transcript level, was introduced into Arabidopsis plants by using a vector containing the CaMV35S promoter. These procedures allowed identifying the key genes contributing to differences in disease resistance between a strongly resistant accession of a wild grapevine species Vitis davidii (VID) and a susceptible cultivar of V. vinifera, 'Manicure Finger' (VIV). Vitis davidii, but not VIV, showed a typical hypersensitive response after infection with a fungal pathogen (Coniella diplodiella) causing white rot disease. Further, 20 defense-related genes were identified, and their differential expression between the two grapevine species was confirmed using quantitative real-time PCR analysis. VdWRKY53, showing the highest transcript level, was selected for functional analysis and therefore over-expressed in Arabidopsis under the control of the CaMV35S promoter. The transgenic plants showed enhanced resistance to C. diplodiella and to two other pathogens, Pseudomonas syringae pv. tomato DC3000 and Golovinomyces cichoracearum. CONCLUSION: The consistency of the results in VID and transgenic Arabidopsis indicated that VdWRKY53 might be involved in the activation of defense-related genes that enhance the resistance of these plants to pathogens. Thus, the over-expression of VdWRKY53 in transgenic grapevines might improve their resistance to pathogens.201931057347
874860.9417Heterologous Expression of the Constitutive Disease Resistance 2 and 8 Genes from Poncirus trifoliata Restored the Hypersensitive Response and Resistance of Arabidopsis cdr1 Mutant to Bacterial Pathogen Pseudomonas syringae. Huanglongbing (HLB), also known as citrus greening, is the most destructive disease of citrus worldwide. In the United States, this disease is associated with a phloem-restricted bacterium, Candidatus Liberibacter asiaticus. Commercial citrus cultivars are susceptible to HLB, but Poncirus trifoliata, a close relative of Citrus, is highly tolerant of HLB. Isolating P. trifoliata gene(s) controlling its HLB tolerance followed by expressing the gene(s) in citrus is considered a potential cisgenic approach to engineering citrus for tolerance to HLB. Previous gene expression studies indicated that the constitutive disease resistance (CDR) genes in P. trifoliata (PtCDRs) may play a vital role in its HLB tolerance. This study was designed to use Arabidopsis mutants as a model system to confirm the function of PtCDRs in plant disease resistance. PtCDR2 and PtCDR8 were amplified from P. trifoliata cDNA and transferred into the Arabidopsis cdr1 mutant, whose resident CDR1 gene was disrupted by T-DNA insertion. The PtCDR2 and PtCDR8 transgenic Arabidopsis cdr1 mutant restored its hypersensitive response to the bacterial pathogen Pseudomonas syringae pv. tomato strain DC3000 (Pst DC3000) expressing avrRpt2. The defense marker gene PATHOGENESIS RELATED 1 (PR1) expressed at much higher levels in the PtCDR2 or PtCDR8 transgenic cdr1 mutant than in the non-transgenic cdr1 mutant with or without pathogen infection. Multiplication of Pst DC3000 bacteria in Arabidopsis was inhibited by the expression of PtCDR2 and PtCDR8. Our results showed that PtCDR2 and PtCDR8 were functional in Arabidopsis and played a positive role in disease resistance and demonstrated that Arabidopsis mutants can be a useful alternate system for screening Poncirus genes before making the time-consuming effort to transfer them into citrus, a perennial woody plant that is highly recalcitrant for Agrobacterium or biolistic-mediated transformation.202032629813
53770.9416Omegon-Km: a transposable element designed for in vivo insertional mutagenesis and cloning of genes in gram-negative bacteria. To combine the features of the omega interposons with the advantages of in vivo transposition mutagenesis, we have constructed an artificial transposon, called Omegon-Km. The Omegon-Km transposon is carried on the plasmid pJFF350 which can be conjugally mobilized into a broad range of Gram-negative bacteria. Omegon-Km is flanked, in inverted orientation, by synthetic 28-bp repeats derived from the ends of IS1. In addition, each end of Omegon-Km has the very efficient transcription and translation terminators of the omega interposon. Internally, Omegon-Km carries the selectable kanamycin (Km)-neomycin resistance gene (alph A) which is expressed well in many Gram-negative bacteria. The IS1 transposition functions are located on the donor plasmid but external to Omegon-Km. Thus, insertions of Omegon-Km are very stable because they lack the capacity for further transposition. Omegon-Km mutagenesis is performed by conjugal transfer of pJFF350 from Escherichia coli into any Gram-negative recipient strain in which this plasmid is unable to replicate. Those cells which have had a transposition event are selected by their resistance to Km. Very high frequencies of Omegon-Km transposition were observed in Pseudomonas putida. Preliminary experiments with other Gram-negative soil and water bacteria (Rhizobium leguminosarum, Paracoccus denitrificans) yielded mutants at reasonable levels. The presence of an E. coli-specific origin of replication (ori) within Omegon-Km allows the rapid and easy cloning, in E. coli, of the nucleotide sequences flanking the site of the transposition event.19892546859
601780.9415Selection of lactic acid bacteria to promote an efficient silage fermentation capable of inhibiting the activity of Aspergillus parasiticus and Fusarium gramineraum and mycotoxin production. AIMS: To select lactic acid bacteria with potential silage inoculant properties. The bio-control activity against mycotoxicogenic fungi and the presence of antibiotics resistance gene were also evaluated. METHODS AND RESULTS: Lactobacillus rhamnosus RC007 and Lactobacillus plantarum RC009 were selected on the basis of growth rate and efficacy in reducing the pH of maize extract medium; therefore, they were evaluated for their bio-control ability against Fusarium graminearum and Aspergillus parasiticus. Studies on lag phase, growth rate and aflatoxin B1 (AFB1) and zearalenone (ZEA) production were carried out in vitro under different regimes of aw (0·95 and 0·99); pH (4 and 6); temperature (25 and 37°C); and oxygen availability (normal and reduced). Lactobacillus rhamnosus RC007 was able to completely inhibit the F. graminearum growth at all assayed conditions, while Lact. plantarum RC009 only did it at pH 4. Both Lactobacillus strains were able to significantly reduce the A. parasiticus growth rate mainly at 0·99 aw . A decrease in ZEA production was observed as result of Lactobacillus strains -F. graminearum interaction; however, the A. parasiticus- Lact. plantarum interaction resulted in an increased AFB1 production. Lactobacillus rhamnosus RC007 proved to have no genes for resistance to the tested antibiotics. CONCLUSIONS: The ability of Lact. rhamnosus RC007 to rapidly drop the pH and to inhibit fungal growth and mycotoxin production and the absence of antibiotic resistance genes shows the potential of its application as inoculant and bio-control agent in animal feed. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated the importance of selecting bacteria for silage inoculants not only for the improvement of silage fermentation but also for their effects on mycotoxicogenic fungi and the resulting mycotoxin production due to the risk that they may involve.201323437822
608390.9414Bioactivity 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
437100.9413Cloning of genes responsible for acetic acid resistance in Acetobacter aceti. Five acetic acid-sensitive mutants of Acetobacter aceti subsp. aceti no. 1023 were isolated by mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. Three recombinant plasmids that complemented the mutations were isolated from a gene bank of the chromosome DNA of the parental strain constructed in Escherichia coli by using cosmid vector pMVC1. One of these plasmids (pAR1611), carrying about a 30-kilobase-pair (kb) fragment that conferred acetic acid resistance to all five mutants, was further analyzed. Subcloning experiments indicated that a 8.3-kb fragment was sufficient to complement all five mutations. To identify the mutation loci and genes involved in acetic acid resistance, insertional inactivation was performed by insertion of the kanamycin resistance gene derived from E. coli plasmid pACYC177 into the cloned 8.3-kb fragment and successive integration into the chromosome of the parental strain. The results suggested that three genes, designated aarA, aarB, and aarC, were responsible for expression of acetic acid resistance. Gene products of these genes were detected by means of overproduction in E. coli by use of the lac promoter. The amino acid sequence of the aarA gene product deduced from the nucleotide sequence was significantly similar to those of the citrate synthases (CSs) of E. coli and other bacteria. The A. aceti mutants defective in the aarA gene were found to lack CS activity, which was restored by introduction of a plasmid containing the aarA gene. A mutation in the CS gene of E. coli was also complemented by the aarA gene. These results indicate that aarA is the CS gene.19902156811
6167110.9411Differential gene expression in Escherichia coli during aerosolization from liquid suspension. Comparative transcriptome analysis was used to determine the differentially expressed genes in Escherichia coli during aerosolization from liquid suspension. Isogenic mutant studies were then used to examine the potential part played by some of these genes in bacterial survival in the air. Bioaerosols were sampled after 3 min of nebulization, which aerosolized the bacteria from the liquid suspension to an aerosol chamber (A0), and after further 30 min of airborne suspension in the chamber (A30). Bacteria at A0 showed 65 differentially expressed genes (30 downregulated and 35 upregulated) as compared to the original bacteria in the nebulizer. Droplet evaporation models predicted a drop in temperature in the bioaerosols, which coincides with the change in the expression of cold shock protein genes-cspB and cspG in the bacteria. The most notable group of differentially expressed genes was sorbitol transport and metabolism genes (srlABDEMR). Other genes associated with osmotic stress, nutrient limitation, DNA damage, and other stresses were differentially expressed in the bacteria at A0. After further airborne suspension, one gene (ypfM, which encodes a hypothetical protein with unknown function) was downregulated in the bacteria at A30 as compared to those at A0. Finally, isogenic mutants with either the dps or srlA gene deleted (both genes were upregulated at A0) had lower survival than the parental strain, which is a sign of their potential ability to protect the bacteria in the air.201829808326
8676120.9410Induced Mutagenesis and Comparative Genomics of Raoultella sp. 64 for Enhanced Antimony Resistance and Biosorption. Antimony-resistant bacteria are potential natural resources for the bioremediation of mining soil pollution. A Raoultella sp. 64 strain was isolated from antimony-contaminated soil. To enhance its Sb resistance abilities, this strain was transported into space aboard the Shenzhou spacecraft for space breeding, resulting in a mutant strain, Raoultella sp. D9. The whole genomes of Raoultella sp. 64 and mutant strain Raoultella sp. D9 were sequenced, revealing the genomic information for the bacterium. Comparative genomic analysis was then carried out to identify differential functional genes. The adsorption conditions for Sb(III) were optimized and refined. Further, Fourier transform infrared spectroscopy (FTIR) was used to determine the adsorption of antimony. Results show that strain D9 exhibits a higher tolerance to Sb(III), and Sb resistance genes were identified in both Raoultella sp. 64 and D9. Analysis of the differential functional genes indicated that the increased copy number of plsX may lead to a higher lipid content in the cell membrane, thereby enhancing the cell's resistance to heavy metals. Mutant strain D9 exhibited better biosorption capacity compared to strain 64. FTIR studies showed that key functional groups, including -OH, C-N, C-H, and C-O, are likely to have participated in Sb(III) biosorption. Further study of the differential functional genes could provide a basis for future research and the subsequent development of technologies for the remediation of Sb-contaminated sites.202540284716
6160130.9408Comparative transcriptional profiling of tildipirosin-resistant and sensitive Haemophilus parasuis. Numerous studies have been conducted to examine the molecular mechanism of Haemophilus parasuis resistance to antibiotic, but rarely to tildipirosin. In the current study, transcriptional profiling was applied to analyse the variation in gene expression of JS0135 and tildipirosin-resistant JS32. The growth curves showed that JS32 had a higher growth rate but fewer bacteria than JS0135. The cell membranes of JS32 and a resistant clinical isolate (HB32) were observed to be smoother than those of JS0135. From the comparative gene expression profile 349 up- and 113 downregulated genes were observed, covering 37 GO and 63 KEGG pathways which are involved in biological processes (11), cellular components (17), molecular function (9), cellular processes (1), environmental information processing (4), genetic information processing (9) and metabolism (49) affected in JS32. In addition, the relative overexpression of genes of the metabolism pathway (HAPS_RS09315, HAPS_RS09320), ribosomes (HAPS_RS07815) and ABC transporters (HAPS_RS10945) was detected, particularly the metabolism pathway, and verified with RT-qPCR. Collectively, the gene expression profile in connection with tildipirosin resistance factors revealed unique and highly resistant determinants of H. parasuis to macrolides that warrant further attention due to the significant threat of bacterial resistance.201728790420
2094140.9408Evaluation of the antibacterial activity of Weissella confusa K3 cell-free supernatant against extended-spectrum βeta lactamase (ESBL) producing uropathogenic Escherichia coli U60. Different strategies have been approved for controlling extended-spectrum βeta lactamase (ESBL) producing uropathogenic bacteria. The antibacterial activity of Lactic acid bacteria (LAB) is an effective strategy due to its probiotic characteristics and beneficial effects on human health. The antibiotic susceptibility test, disk diffusion method, and double disc synergy test indicated that five enteric uropathogenic isolates were ESBL producers during the present study. They recorded diameters of inhibition zones as ≤ 18, ≤ 8, ≤ 19, and ≤ 8 mm against cefotaxime (CTX), ceftazidime (CAZ), aztreonam (ATM), and ceftriaxone (CRO). Genotypically, bla(TEM) genes are the most common, with (100 %) occurrence in all the five enteric tested uropathogens, followed by bla(SHV) and bla(CTX) genes (60 %). In addition, out of 10 LAB isolates from dairy products, the CFS of isolate no. K3 had high antibacterial activity against the tested ESBLs, especially no. U60, with a MIC of 600 µl. Additionally, the MIC and sub-MIC of K3 CFS inhibited the production of antibiotic-resistant bla (TEM) genes of U60. Analyzing the 16S rRNA sequence confirmed that the most potent ESBL-producing bacteria (U60) and LAB (K3) isolates were identified as Escherichia coli U60.1 and Weissella confuse K3 with accession numbers MW173246 and MW173299.1, respectively, in GenBank.202336873575
5221150.9407Molecular 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
6085160.9407Heavy 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
6211170.9406Natural resistance to salmonellae in mice: control by genes within the major histocompatibility complex. Determinations of 50% lethal dose (LD50) values in H-2 congenic B10 lines showed that late-emerging resistance (postimmune response phase) to salmonellae of intermediate virulence was less in H-2b and H-2d than in H-2a, H-2k, and H-2f mice. Association of resistance to H-2 was confirmed by backcross analysis, and LD50 determinations on H-2 recombinant haplotype strains showed that resistance maps to the I-E subregion. Bacterial growth curves in liver and spleen showed that susceptible mice carried bacteria for longer in the reticuloendothelial system than did resistant mice and that susceptible mice showed greater splenomegaly. Association of resistance and susceptibility to H-2 was not different when sister transductant salmonellae expressing somatic antigens O4 and O9 were used. Thus a gene(s) within the major histocompatibility complex controls natural resistance to salmonellae in mice by influencing the ability to clear bacteria from the reticuloendothelial system in the later phase of the infection, and the immunodominant O antigen cannot be solely involved.19852413142
6212180.9405Strain differences in the susceptibility and resistance of Pasteurella multocida to phagocytosis and killing by rabbit polymorphonuclear neutrophils. The interactions of 2 capsular serotype A and 4 serotype D strains of Pasteurella multocida with rabbit polymorphonuclear neutrophils (PMN) were compared in vitro, using a PMN phagocytic and bactericidal assay. Bacteria and rabbit PMN were incubated for 15 minutes. The suspensions were subjected to differential centrifugation and the percentage of phagocytosis (cell association) was determined from the number of viable noncell-associated bacteria. The cell pellets and the associated bacteria were resuspended and PMN bactericidal activity was calculated from the number of remaining viable cell-associated bacteria at 45 and 75 minutes after the start of the assay. Test bacteria were not opsonized or were opsonized with immune serum containing active complement. One type A strain was ingested and killed by PMN in the presence and absence of opsonins. The 5 remaining strains were resistant to PMN killing, but only the type A strain resisted phagocytosis. Resistance of the type A strain was attributed to the hyaluronic acid capsule, since pretreatment of the bacteria with hyaluronidase rendered opsonized bacteria susceptible to ingestion and killing. The pattern of resistance of the 4 type D strains was different from that of the resistant type A strain. Both opsonized and nonopsonized type D bacteria became cell associated, but none were killed by PMN. The mechanism of resistance of these 4 strains to PMN bactericidal activity is currently unknown.19846742581
516190.9405Role of Iron-Containing Alcohol Dehydrogenases in Acinetobacter baumannii ATCC 19606 Stress Resistance and Virulence. Most bacteria possess alcohol dehydrogenase (ADH) genes (Adh genes) to mitigate alcohol toxicity, but these genes have functions beyond alcohol degradation. Previous research has shown that ADH can modulate quorum sensing in Acinetobacter baumannii, a rising opportunistic pathogen. However, the number and nature of Adh genes in A. baumannii have not yet been fully characterized. We identified seven alcohol dehydrogenases (NAD(+)-ADHs) from A. baumannii ATCC 19606, and examined the roles of three iron-containing ADHs, ADH3, ADH4, and ADH6. Marker-less mutation was used to generate Adh3, Adh4, and Adh6 single, double, and triple mutants. Disrupted Adh4 mutants failed to grow in ethanol-, 1-butanol-, or 1-propanol-containing mediums, and recombinant ADH4 exhibited strongest activity against ethanol. Stress resistance assays with inorganic and organic hydroperoxides showed that Adh3 and Adh6 were key to oxidative stress resistance. Virulence assays performed on the Galleria mellonella model organism revealed that Adh4 mutants had comparable virulence to wild-type, while Adh3 and Adh6 mutants had reduced virulence. The results suggest that ADH4 is primarily involved in alcohol metabolism, while ADH3 and ADH6 are key to stress resistance and virulence. Further investigation into the roles of other ADHs in A. baumannii is warranted.202134576087