# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 801 | 0 | 0.9596 | Redox-sensitive transcriptional regulator SoxR directly controls antibiotic production, development and thiol-oxidative stress response in Streptomyces avermitilis. The redox-sensitive transcriptional regulator SoxR is conserved in bacteria. Its role in mediating protective response to various oxidative stresses in Escherichia coli and related enteric bacteria has been well established. However, functions and regulatory mechanisms of SoxR in filamentous Streptomyces, which produce half of known antibiotics, are unclear. We report here that SoxR pleiotropically regulates antibiotic production, morphological development, primary metabolism and thiol-oxidative stress response in industrially important species Streptomyces avermitilis. SoxR stimulated avermectin production by directly activating ave structural genes. Four genes (sav_3956, sav_4018, sav_5665 and sav_7218) that are homologous to targets of S. coelicolor SoxR are targeted by S. avermitilis SoxR. A consensus 18-nt SoxR-binding site, 5'-VSYCNVVMHNKVKDGMGB-3', was identified in promoter regions of sav_3956, sav_4018, sav_5665, sav_7218 and target ave genes, leading to prediction of the SoxR regulon and confirmation of 11 new targets involved in development (ftsH), oligomycin A biosynthesis (olmRI), primary metabolism (metB, sav_1623, plcA, nirB, thiG, ndh2), transport (smoE) and regulatory function (sig57, sav_7278). SoxR also directly activated three key developmental genes (amfC, whiB and ftsZ) and promoted resistance of S. avermitilis to thiol-oxidative stress through activation of target trx and msh genes. Overexpression of soxR notably enhanced antibiotic production in S. avermitilis and S. coelicolor. Our findings expand our limited knowledge of SoxR and will facilitate improvement of methods for antibiotic overproduction in Streptomyces species. | 2022 | 33951287 |
| 803 | 1 | 0.9509 | Nucleotide 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. | 1992 | 1624446 |
| 802 | 2 | 0.9476 | YqhC 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. | 2011 | 20676725 |
| 6146 | 3 | 0.9462 | Arsenic 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. | 2017 | 28054716 |
| 517 | 4 | 0.9461 | Adaptation to metal(loid)s in strain Mucilaginibacter rubeus P2 involves novel arsenic resistance genes and mechanisms. Arsenic is a ubiquitous environmental toxi substance that affects human health. Compared to inorganic arsenicals, reduced organoarsenicals are more toxic, and some of them are recognized as antibiotics, such as methylarsenite [MAs(III)] and arsinothricin (2-amino-4-(hydroxymethylarsinoyl)butanoate, or AST). To date, organoarsenicals such as MAs(V) and roxarsone [Rox(V)] are still used in agriculture and animal husbandry. How bacteria deal with both inorganic and organoarsenic species is unclear. Recently, we identified an environmental isolate Mucilaginibacter rubeus P2 that has adapted to high arsenic and antinomy levels by triplicating an arsR-mrarsU(Bact)-arsN-arsC-(arsRhp)-hp-acr3-mrme1(Bact)-mrme2(Bact)gene cluster. Heterologous expression of mrarsM(Bact), mrarsU(Bact), mrme1(Bact) and mrme2(Bact), encoding putative arsenic resistance determinants, in the arsenic hypersensitive strain Escherichia coli AW3110 conferred resistance to As(III), As(V), MAs(III) or Rox(III). Our data suggest that metalloid exposure promotes plasticity in arsenic resistance systems, enhancing host organism adaptation to metalloid stress. | 2024 | 37865075 |
| 8826 | 5 | 0.9456 | Transcriptome Analysis of Komagataeibacter europaeus CGMCC 20445 Responses to Different Acidity Levels During Acetic Acid Fermentation. In the industrial production of high-acidity vinegar, the initial ethanol and acetic acid concentrations are limiting factors that will affect acetic acid fermentation. In this study, Komagataeibacter europaeus CGMCC 20445 was used for acetic acid shake flask fermentation at an initial ethanol concentration of 4.3% (v/v). We conducted transcriptome analysis of K. europaeus CGMCC 20445 samples under different acidity conditions to elucidate the changes in differentially expressed genes throughout the fermentation process. We also analyzed the expression of genes associated with acid-resistance mechanisms. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that the differentially expressed genes were enriched in ribosomes, citrate cycle, butanoate metabolism, oxidative phosphorylation, pentose phosphate, and the fatty acid biosynthetic pathways. In addition, this study found that K. europaeus CGMCC 20445 regulates the gene expression levels of cell envelope proteins and stress-responsive proteins to adapt to the gradual increase in acidity during acetic acid fermentation. This study improved the understanding of the acid resistance mechanism of K. europaeus and provided relevant reference information for the further genetic engineering of this bacterium. | 2021 | 34584524 |
| 6349 | 6 | 0.9453 | High-level chromate resistance in Arthrobacter sp. strain FB24 requires previously uncharacterized accessory genes. BACKGROUND: The genome of Arthrobacter sp. strain FB24 contains a chromate resistance determinant (CRD), consisting of a cluster of 8 genes located on a 10.6 kb fragment of a 96 kb plasmid. The CRD includes chrA, which encodes a putative chromate efflux protein, and three genes with amino acid similarities to the amino and carboxy termini of ChrB, a putative regulatory protein. There are also three novel genes that have not been previously associated with chromate resistance in other bacteria; they encode an oxidoreductase (most similar to malate:quinone oxidoreductase), a functionally unknown protein with a WD40 repeat domain and a lipoprotein. To delineate the contribution of the CRD genes to the FB24 chromate [Cr(VI)] response, we evaluated the growth of mutant strains bearing regions of the CRD and transcript expression levels in response to Cr(VI) challenge. RESULTS: A chromate-sensitive mutant (strain D11) was generated by curing FB24 of its 96-kb plasmid. Elemental analysis indicated that chromate-exposed cells of strain D11 accumulated three times more chromium than strain FB24. Introduction of the CRD into strain D11 conferred chromate resistance comparable to wild-type levels, whereas deletion of specific regions of the CRD led to decreased resistance. Using real-time reverse transcriptase PCR, we show that expression of each gene within the CRD is specifically induced in response to chromate but not by lead, hydrogen peroxide or arsenate. Higher levels of chrA expression were achieved when the chrB orthologs and the WD40 repeat domain genes were present, suggesting their possible regulatory roles. CONCLUSION: Our findings indicate that chromate resistance in Arthrobacter sp. strain FB24 is due to chromate efflux through the ChrA transport protein. More importantly, new genes have been identified as having significant roles in chromate resistance. Collectively, the functional predictions of these additional genes suggest the involvement of a signal transduction system in the regulation of chromate efflux and warrants further study. | 2009 | 19758450 |
| 150 | 7 | 0.9450 | Identification of Resistance Genes and Response to Arsenic in Rhodococcus aetherivorans BCP1. Arsenic (As) ranks among the priority metal(loid)s that are of public health concern. In the environment, arsenic is present in different forms, organic or inorganic, featured by various toxicity levels. Bacteria have developed different strategies to deal with this toxicity involving different resistance genetic determinants. Bacterial strains of Rhodococcus genus, and more in general Actinobacteria phylum, have the ability to cope with high concentrations of toxic metalloids, although little is known on the molecular and genetic bases of these metabolic features. Here we show that Rhodococcus aetherivorans BCP1, an extremophilic actinobacterial strain able to tolerate high concentrations of organic solvents and toxic metalloids, can grow in the presence of high concentrations of As(V) (up to 240 mM) under aerobic growth conditions using glucose as sole carbon and energy source. Notably, BCP1 cells improved their growth performance as well as their capacity of reducing As(V) into As(III) when the concentration of As(V) is within 30-100 mM As(V). Genomic analysis of BCP1 compared to other actinobacterial strains revealed the presence of three gene clusters responsible for organic and inorganic arsenic resistance. In particular, two adjacent and divergently oriented ars gene clusters include three arsenate reductase genes (arsC1/2/3) involved in resistance mechanisms against As(V). A sequence similarity network (SSN) and phylogenetic analysis of these arsenate reductase genes indicated that two of them (ArsC2/3) are functionally related to thioredoxin (Trx)/thioredoxin reductase (TrxR)-dependent class and one of them (ArsC1) to the mycothiol (MSH)/mycoredoxin (Mrx)-dependent class. A targeted transcriptomic analysis performed by RT-qPCR indicated that the arsenate reductase genes as well as other genes included in the ars gene cluster (possible regulator gene, arsR, and arsenite extrusion genes, arsA, acr3, and arsD) are transcriptionally induced when BCP1 cells were exposed to As(V) supplied at two different sub-lethal concentrations. This work provides for the first time insights into the arsenic resistance mechanisms of a Rhodococcus strain, revealing some of the unique metabolic requirements for the environmental persistence of this bacterial genus and its possible use in bioremediation procedures of toxic metal contaminated sites. | 2019 | 31133997 |
| 131 | 8 | 0.9448 | Characterization of Two Highly Arsenic-Resistant Caulobacteraceae Strains of Brevundimonas nasdae: Discovery of a New Arsenic Resistance Determinant. Arsenic (As), distributed widely in the natural environment, is a toxic substance which can severely impair the normal functions in living cells. Research on the genetic determinants conferring functions in arsenic resistance and metabolism is of great importance for remediating arsenic-contaminated environments. Many organisms, including bacteria, have developed various strategies to tolerate arsenic, by either detoxifying this harmful element or utilizing it for energy generation. More and more new arsenic resistance (ars) determinants have been identified to be conferring resistance to diverse arsenic compounds and encoded in ars operons. There is a hazard in mobilizing arsenic during gold-mining activities due to gold- and arsenic-bearing minerals coexisting. In this study, we isolated 8 gold enrichment strains from the Zijin gold and copper mine (Longyan, Fujian Province, China) wastewater treatment site soil, at an altitude of 192 m. We identified two Brevundimonas nasdae strains, Au-Bre29 and Au-Bre30, among these eight strains, having a high minimum inhibitory concentration (MIC) for As(III). These two strains contained the same ars operons but displayed differences regarding secretion of extra-polymeric substances (EPS) upon arsenite (As(III)) stress. B. nasdae Au-Bre29 contained one extra plasmid but without harboring any additional ars genes compared to B. nasdae Au-Bre30. We optimized the growth conditions for strains Au-Bre29 and Au-Bre30. Au-Bre30 was able to tolerate both a lower pH and slightly higher concentrations of NaCl. We also identified folE, a folate synthesis gene, in the ars operon of these two strains. In most organisms, folate synthesis begins with a FolE (GTP-Cyclohydrolase I)-type enzyme, and the corresponding gene is typically designated folE (in bacteria) or gch1 (in mammals). Heterologous expression of folE, cloned from B. nasdae Au-Bre30, in the arsenic-hypersensitive strain Escherichia coli AW3110, conferred resistance to As(III), arsenate (As(V)), trivalent roxarsone (Rox(III)), pentavalent roxarsone (Rox(V)), trivalent antimonite (Sb(III)), and pentavalent antimonate (Sb(V)), indicating that folate biosynthesis is a target of arsenite toxicity and increased production of folate confers increased resistance to oxyanions. Genes encoding Acr3 and ArsH were shown to confer resistance to As(III), Rox(III), Sb(III), and Sb(V), and ArsH also conferred resistance to As(V). Acr3 did not confer resistance to As(V) and Rox(V), while ArsH did not confer resistance to Rox(V). | 2022 | 35628430 |
| 499 | 9 | 0.9446 | Characterization of the genomically encoded fosfomycin resistance enzyme from Mycobacterium abscessus. Mycobacterium abscessus belongs to a group of rapidly growing mycobacteria (RGM) and accounts for approximately 65-80% of lung disease caused by RGM. It is highly pathogenic and is considered the prominent Mycobacterium involved in pulmonary infection in patients with cystic fibrosis and chronic pulmonary disease (CPD). FosM is a putative 134 amino acid fosfomycin resistance enzyme from M. abscessus subsp. bolletii that shares approximately 30-55% sequence identity with other vicinal oxygen chelate (VOC) fosfomycin resistance enzymes and represents the first of its type found in any Mycobacterium species. Genes encoding VOC fosfomycin resistance enzymes have been found in both Gram-positive and Gram-negative pathogens. Given that FosA enzymes from Gram-negative bacteria have evolved optimum activity towards glutathione (GSH) and FosB enzymes from Gram-positive bacteria have evolved optimum activity towards bacillithiol (BSH), it was originally suggested that FosM might represent a fourth class of enzyme that has evolved to utilize mycothiol (MSH). However, a sequence similarity network (SSN) analysis identifies FosM as a member of the FosX subfamily, indicating that it may utilize water as a substrate. Here we have synthesized MSH and characterized FosM with respect to divalent metal ion activation and nucleophile selectivity. Our results indicate that FosM is a Mn(2+)-dependent FosX-type hydrase with no selectivity toward MSH or other thiols as analyzed by NMR and mass spectroscopy. | 2019 | 32952996 |
| 810 | 10 | 0.9445 | Draft genome sequencing and functional annotation and characterization of biofilm-producing bacterium Bacillus novalis PD1 isolated from rhizospheric soil. Biofilm forming bacterium Bacillus novalis PD1 was isolated from the rhizospheric soil of a paddy field. B. novalis PD1 is a Gram-positive, facultatively anaerobic, motile, slightly curved, round-ended, and spore-forming bacteria. The isolate B. novalis PD1 shares 98.45% similarity with B. novalis KB27B. B. vireti LMG21834 and B. drentensis NBRC 102,427 are the closest phylogenetic neighbours for B. novalis PD1. The draft genome RAST annotation showed a linear chromosome with 4,569,088 bp, encoding 6139 coding sequences, 70 transfer RNA (tRNA), and 11 ribosomal RNA (rRNA) genes. The genomic annotation of biofilm forming B. novalis PD1(> 3.6@OD(595nm)) showed the presence of exopolysaccharide-forming genes (ALG, PSL, and PEL) as well as other biofilm-related genes (comER, Spo0A, codY, sinR, TasA, sipW, degS, and degU). Antibiotic inactivation gene clusters (ANT (6)-I, APH (3')-I, CatA15/A16 family), efflux pumps conferring antibiotic resistance genes (BceA, BceB, MdtABC-OMF, MdtABC-TolC, and MexCD-OprJ), and secondary metabolites linked to phenazine, terpene, and beta lactone gene clusters are part of the genome. | 2021 | 34537868 |
| 544 | 11 | 0.9445 | Organic Hydroperoxide Induces Prodigiosin Biosynthesis in Serratia sp. ATCC 39006 in an OhrR-Dependent Manner. The biosynthesis of prodigiosin in the model prodigiosin-producing strain, Serratia sp. ATCC 39006, is significantly influenced by environmental and cellular signals. However, a comprehensive regulatory mechanism for this process has not been well established. In the present study, we demonstrate that organic hydroperoxide activates prodigiosin biosynthesis in an OhrR-dependent manner. Specifically, the MarR-family transcriptional repressor OhrR (Ser39006_RS05455) binds to its operator located far upstream of the promoter region of the prodigiosin biosynthesis operon (319 to 286 nucleotides [nt] upstream of the transcription start site) and negatively regulates the expression of prodigiosin biosynthesis genes. Organic hydroperoxide disassociates the binding between OhrR and its operator, thereby promoting the prodigiosin production. Moreover, OhrR modulates the resistance of Serratia sp. ATCC 39006 to organic hydroperoxide by regulating the transcription of its own gene and the downstream cotranscribed ohr gene. These results demonstrate that OhrR is a pleiotropic repressor that modulates the prodigiosin production and the resistance of Serratia sp. ATCC 39006 to organic hydroperoxide stress. IMPORTANCE Bacteria naturally encounter various environmental and cellular stresses. Organic hydroperoxides generated from the oxidation of polyunsaturated fatty acids are widely distributed and usually cause lethal oxidative stress by damaging cellular components. OhrR is known as a regulator that modulates the resistance of bacteria to organic hydroperoxide stress. In the current study, organic hydroperoxide disassociates OhrR from the promoter of prodigiosin biosynthesis gene cluster, thus promoting transcription of pigA to -O genes. In this model, organic hydroperoxide acts as an inducer of prodigiosin synthesis in Serratia sp. ATCC 39006. These results improve our understanding of the regulatory network of prodigiosin synthesis and serve as an example for identifying the cross talk between the stress responses and the regulation of secondary metabolism. | 2022 | 35044847 |
| 6134 | 12 | 0.9445 | Complete genome and gene expression analyses of Asaia bogorensis reveal unique responses to culture with mammalian cells as a potential opportunistic human pathogen. Asaia bogorensis, a member of acetic acid bacteria (AAB), is an aerobic bacterium isolated from flowers and fruits, as well as an opportunistic pathogen that causes human peritonitis and bacteraemia. Here, we determined the complete genomic sequence of the As. bogorensis type strain NBRC 16594, and conducted comparative analyses of gene expression under different conditions of co-culture with mammalian cells and standard AAB culture. The genome of As. bogorensis contained 2,758 protein-coding genes within a circular chromosome of 3,198,265 bp. There were two complete operons encoding cytochrome bo3-type ubiquinol terminal oxidases: cyoABCD-1 and cyoABCD-2. The cyoABCD-1 operon was phylogenetically common to AAB genomes, whereas the cyoABCD-2 operon belonged to a lineage distinctive from the cyoABCD-1 operon. Interestingly, cyoABCD-1 was less expressed under co-culture conditions than under the AAB culture conditions, whereas the converse was true for cyoABCD-2. Asaia bogorensis shared pathogenesis-related genes with another pathogenic AAB, Granulibacter bethesdensis, including a gene coding pathogen-specific large bacterial adhesin and additional genes for the inhibition of oxidation and antibiotic resistance. Expression alteration of the respiratory chain and unique hypothetical genes may be key traits that enable the bacterium to survive under the co-culture conditions. | 2015 | 26358298 |
| 6083 | 13 | 0.9445 | Bioactivity 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. | 2024 | 38189906 |
| 129 | 14 | 0.9444 | Evidence for vital role of endo-β-N-acetylglucosaminidase in the resistance of Arthrobacter protophormiae RKJ100 towards elevated concentrations of o-nitrobenzoate. Arthrobacter protophormiae RKJ100 was previously characterized for its ability to tolerate extremely high concentrations of o-nitrobenzoate (ONB), a toxic xenobiotic environmental pollutant. The physiological responses of strain RKJ100 to ≥30 mM ONB indicated towards a resistance mechanism manifested via alteration of cell morphology and cell wall structure. In this study, we aim to characterize gene(s) involved in the resistance of strain RKJ100 towards extreme concentrations (i.e. 150 mM) of ONB. Transposon mutagenesis was carried out to generate a mutant library of strain RKJ100, which was then screened for ONB-sensitive mutants. A sensitive mutant was defined and selected as one that could not tolerate ≥30 mM ONB. Molecular and biochemical characterization of this mutant showed that the disruption of endo-β-N-acetylglucosaminidase (ENGase) gene caused the sensitivity. ENGase is an important enzyme for oligosaccharide processing and cell wall recycling in bacteria, fungi, plants and animals. Previous reports have already indicated several possible roles of this enzyme in cellular homeostasis. Results presented here provide the first evidence for its involvement in bacterial resistance towards extreme concentrations of a toxic xenobiotic compound and also suggest that strain RKJ100 employs ENGase as an important component in osmotic shock response for resisting extreme concentrations of ONB. | 2014 | 24562786 |
| 42 | 15 | 0.9443 | Suppression of the rice fatty-acid desaturase gene OsSSI2 enhances resistance to blast and leaf blight diseases in rice. Fatty acids and their derivatives play important signaling roles in plant defense responses. It has been shown that suppressing a gene for stearoyl acyl carrier protein fatty-acid desaturase (SACPD) enhances the resistance of Arabidopsis (SSI2) and soybean to multiple pathogens. In this study, we present functional analyses of a rice homolog of SSI2 (OsSSI2) in disease resistance of rice plants. A transposon insertion mutation (Osssi2-Tos17) and RNAi-mediated knockdown of OsSSI2 (OsSSI2-kd) reduced the oleic acid (18:1) level and increased that of stearic acid (18:0), indicating that OsSSI2 is responsible for fatty-acid desaturase activity. These plants displayed spontaneous lesion formation in leaf blades, retarded growth, slight increase in endogenous free salicylic acid (SA) levels, and SA/benzothiadiazole (BTH)-specific inducible genes, including WRKY45, a key regulator of SA/BTH-induced resistance, in rice. Moreover, the OsSSI2-kd plants showed markedly enhanced resistance to the blast fungus Magnaporthe grisea and leaf-blight bacteria Xanthomonas oryzae pv. oryzae. These results suggest that OsSSI2 is involved in the negative regulation of defense responses in rice, as are its Arabidopsis and soybean counterparts. Microarray analyses identified 406 genes that were differentially expressed (>or=2-fold) in OsSSI2-kd rice plants compared with wild-type rice and, of these, approximately 39% were BTH responsive. Taken together, our results suggest that induction of SA-responsive genes, including WRKY45, is likely responsible for enhanced disease resistance in OsSSI2-kd rice plants. | 2009 | 19522564 |
| 817 | 16 | 0.9442 | Mercury resistance transposons in Bacilli strains from different geographical regions. A total of 65 spore-forming mercury-resistant bacteria were isolated from natural environments worldwide in order to understand the acquisition of additional genes by and dissemination of mercury resistance transposons across related Bacilli genera by horizontal gene movement. PCR amplification using a single primer complementary to the inverted repeat sequence of TnMERI1-like transposons showed that 12 of 65 isolates had a transposon-like structure. There were four types of amplified fragments: Tn5084, Tn5085, Tn(d)MER3 (a newly identified deleted transposon-like fragment) and Tn6294 (a newly identified transposon). Tn(d)MER3 is a 3.5-kb sequence that carries a merRETPA operon with no merB or transposase genes. It is related to the mer operon of Bacillus licheniformis strain FA6-12 from Russia. DNA homology analysis shows that Tn6294 is an 8.5-kb sequence that is possibly derived from Tn(d)MER3 by integration of a TnMERI1-type transposase and resolvase genes and in addition the merR2 and merB1 genes. Bacteria harboring Tn6294 exhibited broad-spectrum mercury resistance to organomercurial compounds, although Tn6294 had only merB1 and did not have the merB2 and merB3 sequences for organomercurial lyases found in Tn5084 of B. cereus strain RC607. Strains with Tn6294 encode mercuric reductase (MerA) of less than 600 amino acids in length with a single N-terminal mercury-binding domain, whereas MerA encoded by strains MB1 and RC607 has two tandem domains. Thus, Tn(d)MER3 and Tn6294 are shorter prototypes for TnMERI1-like transposons. Identification of Tn6294 in Bacillus sp. from Taiwan and in Paenibacillus sp. from Antarctica indicates the wide horizontal dissemination of TnMERI1-like transposons across bacterial species and geographical barriers. | 2016 | 26802071 |
| 123 | 17 | 0.9441 | Genes for all metals--a bacterial view of the periodic table. The 1996 Thom Award Lecture. Bacterial chromosomes have genes for transport proteins for inorganic nutrient cations and oxyanions, such as NH4+, K+, Mg2+, Co2+, Fe3+, Mn2+, Zn2+ and other trace cations, and PO4(3-), SO4(2-) and less abundant oxyanions. Together these account for perhaps a few hundred genes in many bacteria. Bacterial plasmids encode resistance systems for toxic metal and metalloid ions including Ag+, AsO2-, AsO4(3-), Cd2+, Co2+, CrO4(2-), Cu2+, Hg2+, Ni2+, Pb2+, TeO3(2-), Tl+ and Zn2+. Most resistance systems function by energy-dependent efflux of toxic ions. A few involve enzymatic (mostly redox) transformations. Some of the efflux resistance systems are ATPases and others are chemiosmotic ion/proton exchangers. The Cd(2+)-resistance cation pump of Gram-positive bacteria is membrane P-type ATPase, which has been labeled with 32P from [gamma-32P]ATP and drives ATP-dependent Cd2+ (and Zn2+) transport by membrane vesicles. The genes defective in the human hereditary diseases of copper metabolism, Menkes syndrome and Wilson's disease, encode P-type ATPases that are similar to bacterial cadmium ATPases. The arsenic resistance system transports arsenite [As(III)], alternatively with the ArsB polypeptide functioning as a chemiosmotic efflux transporter or with two polypeptides, ArsB and ArsA, functioning as an ATPase. The third protein of the arsenic resistance system is an enzyme that reduces intracellular arsenate [As(V)] to arsenite [As(III)], the substrate of the efflux system. In Gram-negative cells, a three polypeptide complex functions as a chemiosmotic cation/protein exchanger to efflux Cd2+, Zn2+ and Co2+. This pump consists of an inner membrane (CzcA), an outer membrane (CzcC) and a membrane-spanning (CzcB) protein that function together. | 1998 | 9523453 |
| 556 | 18 | 0.9441 | An ArsR/SmtB family member regulates arsenic resistance genes unusually arranged in Thermus thermophilus HB27. Arsenic resistance is commonly clustered in ars operons in bacteria; main ars operon components encode an arsenate reductase, a membrane extrusion protein, and an As-sensitive transcription factor. In the As-resistant thermophile Thermus thermophilus HB27, genes encoding homologues of these proteins are interspersed in the chromosome. In this article, we show that two adjacent genes, TtsmtB, encoding an ArsR/SmtB transcriptional repressor and, TTC0354, encoding a Zn(2+) /Cd(2+) -dependent membrane ATPase are involved in As resistance; differently from characterized ars operons, the two genes are transcribed from dedicated promoters upstream of their respective genes, whose expression is differentially regulated at transcriptional level. Mutants defective in TtsmtB or TTC0354 are more sensitive to As than the wild type, proving their role in arsenic resistance. Recombinant dimeric TtSmtB binds in vitro to both promoters, but its binding capability decreases upon interaction with arsenate and, less efficiently, with arsenite. In vivo and in vitro experiments also demonstrate that the arsenate reductase (TtArsC) is subjected to regulation by TtSmtB. We propose a model for the regulation of As resistance in T. thermophilus in which TtSmtB is the arsenate sensor responsible for the induction of TtArsC which generates arsenite exported by TTC0354 efflux protein to detoxify cells. | 2017 | 28696001 |
| 6077 | 19 | 0.9439 | Brytella acorum gen. nov., sp. nov., a novel acetic acid bacterium from sour beverages. Polyphasic taxonomic and comparative genomic analyses revealed that a series of lambic beer isolates including strain LMG 32668(T) and the kombucha isolate LMG 32879 represent a novel species among the acetic acid bacteria, with Acidomonas methanolica as the nearest phylogenomic neighbor with a valid name. Overall genomic relatedness indices and phylogenomic and physiological analyses revealed that this novel species was best classified in a novel genus for which we propose the name Brytella acorum gen. nov., sp. nov., with LMG 32668(T) (=CECT 30723(T)) as the type strain. The B. acorum genomes encode a complete but modified tricarboxylic acid cycle, and complete pentose phosphate, pyruvate oxidation and gluconeogenesis pathways. The absence of 6-phosphofructokinase which rendered the glycolysis pathway non-functional, and an energy metabolism that included both aerobic respiration and oxidative fermentation are typical metabolic characteristics of acetic acid bacteria. Neither genome encodes nitrogen fixation or nitrate reduction genes, but both genomes encode genes for the biosynthesis of a broad range of amino acids. Antibiotic resistance genes or virulence factors are absent. | 2023 | 37429096 |