# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 267 | 0 | 1.0000 | Molecular characterization of resistance-nodulation-division transporters from solvent- and drug-resistant bacteria in petroleum-contaminated soil. PCR assays for analyzing resistance-nodulation-division transporters from solvent- and drug-resistant bacteria in soil were developed. Sequence analysis of amplicons showed that the PCR successfully retrieved transporter gene fragments from soil. Most of the genes retrieved from petroleum-contaminated soils formed a cluster (cluster PCS) that was distantly related to known transporter genes. Competitive PCR showed that the abundance of PCS genes is increased in petroleum-contaminated soil. | 2005 | 15640241 |
| 268 | 1 | 0.9998 | Amplification of bacitracin transporter genes in the bacitracin producing Bacillus licheniformis. We have amplified the previously cloned and sequenced genes of the bacitracin exporter (bcr), a member of the ATP-binding transport protein family, within the chromosome of the bacitracin producing Bacillus licheniformis. Amplification of the transporter genes was followed by greatly increased bacitracin resistance. Antibiotic production was enhanced at a low level of bcr genes amplification. An enlarged increase in the copy number of the bcr genes negatively affects the overall growth of bacteria. | 1997 | 9418256 |
| 6346 | 2 | 0.9998 | Identification of unknown acid-resistant genes of oral microbiotas in patients with dental caries using metagenomics analysis. Acid resistance is critical for the survival of bacteria in the dental caries oral micro-environment. However, there are few acid-resistant genes of microbiomes obtained through traditional molecular biology experimental techniques. This study aims to try macrogenomics technologies to efficiently identify acid-resistant genes in oral microbes of patients with dental caries. Total DNA was extracted from oral microbiota obtained from thirty dental caries patients and subjected to high-throughput sequencing. This data was used to build a metagenomic library, which was compared to the sequences of two Streptococcus mutant known acid-resistant genes, danK and uvrA, using a BLAST search. A total of 19 and 35 unknown gene sequences showed similarities with S. mutans uvrA and dnaK in the metagenomic library, respectively. Two unknown genes, mo-dnaK and mo-uvrA, were selected for primer design and bioinformatic analysis based on their sequences. Bioinformatics analysis predicted them encoding of a human heat-shock protein (HSP) 70 and an ATP-dependent DNA repair enzyme, respectively, closely related with the acid resistance mechanism. After cloning, these genes were transferred into competent Escherichia coli for acid resistance experiments. E. coli transformed with both genes demonstrated acid resistance, while the survival rate of E. coli transformed with mo-uvrA was significantly higher in an acidic environment (pH = 3). Through this experiment we found that identify unknown acid-resistant genes in oral microbes of patients with caries by establishing a metagenomic library is very efficient. Our results provide an insight into the mechanisms and pathogenesis of dental caries for their treatment without affecting oral probiotics. | 2021 | 33675438 |
| 477 | 3 | 0.9997 | Novel nickel resistance genes from the rhizosphere metagenome of plants adapted to acid mine drainage. Metal resistance determinants have traditionally been found in cultivated bacteria. To search for genes involved in nickel resistance, we analyzed the bacterial community of the rhizosphere of Erica andevalensis, an endemic heather which grows at the banks of the Tinto River, a naturally metal-enriched and extremely acidic environment in southwestern Spain. 16S rRNA gene sequence analysis of rhizosphere DNA revealed the presence of members of five phylogenetic groups of Bacteria and the two main groups of Archaea mostly associated with sites impacted by acid mine drainage (AMD). The diversity observed and the presence of heavy metals in the rhizosphere led us to construct and screen five different metagenomic libraries hosted in Escherichia coli for searching novel nickel resistance determinants. A total of 13 positive clones were detected and analyzed. Insights about their possible mechanisms of resistance were obtained from cellular nickel content and sequence similarities. Two clones encoded putative ABC transporter components, and a novel mechanism of metal efflux is suggested. In addition, a nickel hyperaccumulation mechanism is proposed for a clone encoding a serine O-acetyltransferase. Five clones encoded proteins similar to well-characterized proteins but not previously reported to be related to nickel resistance, and the remaining six clones encoded hypothetical or conserved hypothetical proteins of uncertain functions. This is the first report documenting nickel resistance genes recovered from the metagenome of an AMD environment. | 2007 | 17675438 |
| 3600 | 4 | 0.9997 | Uncultured soil bacteria are a reservoir of new antibiotic resistance genes. Antibiotic resistance genes are typically isolated by cloning from cultured bacteria or by polymerase chain reaction (PCR) amplification from environmental samples. These methods do not access the potential reservoir of undiscovered antibiotic resistance genes harboured by soil bacteria because most soil bacteria are not cultured readily, and PCR detection of antibiotic resistance genes depends on primers that are based on known genes. To explore this reservoir, we isolated DNA directly from soil samples, cloned the DNA and selected for clones that expressed antibiotic resistance in Escherichia coli. We constructed four libraries that collectively contain 4.1 gigabases of cloned soil DNA. From these and two previously reported libraries, we identified nine clones expressing resistance to aminoglycoside antibiotics and one expressing tetracycline resistance. Based on the predicted amino acid sequences of the resistance genes, the resistance mechanisms include efflux of tetracycline and inactivation of aminoglycoside antibiotics by phosphorylation and acetylation. With one exception, all the sequences are considerably different from previously reported sequences. The results indicate that soil bacteria are a reservoir of antibiotic resistance genes with greater genetic diversity than previously accounted for, and that the diversity can be surveyed by a culture-independent method. | 2004 | 15305923 |
| 4368 | 5 | 0.9997 | Phylogenetic analysis of bacterial and archaeal arsC gene sequences suggests an ancient, common origin for arsenate reductase. BACKGROUND: The ars gene system provides arsenic resistance for a variety of microorganisms and can be chromosomal or plasmid-borne. The arsC gene, which codes for an arsenate reductase is essential for arsenate resistance and transforms arsenate into arsenite, which is extruded from the cell. A survey of GenBank shows that arsC appears to be phylogenetically widespread both in organisms with known arsenic resistance and those organisms that have been sequenced as part of whole genome projects. RESULTS: Phylogenetic analysis of aligned arsC sequences shows broad similarities to the established 16S rRNA phylogeny, with separation of bacterial, archaeal, and subsequently eukaryotic arsC genes. However, inconsistencies between arsC and 16S rRNA are apparent for some taxa. Cyanobacteria and some of the gamma-Proteobacteria appear to possess arsC genes that are similar to those of Low GC Gram-positive Bacteria, and other isolated taxa possess arsC genes that would not be expected based on known evolutionary relationships. There is no clear separation of plasmid-borne and chromosomal arsC genes, although a number of the Enterobacteriales (gamma-Proteobacteria) possess similar plasmid-encoded arsC sequences. CONCLUSION: The overall phylogeny of the arsenate reductases suggests a single, early origin of the arsC gene and subsequent sequence divergence to give the distinct arsC classes that exist today. Discrepancies between 16S rRNA and arsC phylogenies support the role of horizontal gene transfer (HGT) in the evolution of arsenate reductases, with a number of instances of HGT early in bacterial arsC evolution. Plasmid-borne arsC genes are not monophyletic suggesting multiple cases of chromosomal-plasmid exchange and subsequent HGT. Overall, arsC phylogeny is complex and is likely the result of a number of evolutionary mechanisms. | 2003 | 12877744 |
| 6344 | 6 | 0.9997 | Acid-resistant genes of oral plaque microbiome from the functional metagenomics. Acid resistance is one of key properties assisting the survival of cariogenic bacteria in a dental caries environment, but only a few genes conferring acid resistance have been identified to data. Functional metagenomics provides a systematic method for investigating commensal DNA to identify genes that encode target functions. Here, the host strain Escherichia coli DH10B and a constructed bidirectional transcription vector pSKII(+)-lacZ contributed to the construction of a metagenomic library, and 46.6 Mb of metagenomic DNA was cloned from carious supragingival plaque of 8children along with screening for lethal functionality. The screen identified 2 positive clones that exhibited a similar aciduric phenotype to that of the positive controls. Bioinformatic analysis revealed that these two genes encoded an ATP/GTP-binding protein and a malate dehydrogenase. Moreover, we also performed functional screening of Streptococcus mutans, since it is one of the predominant cariogenic strains but was not identified in our initial screening. Five positive clones were retrieved. In conclusion, our improved functional metagenomics screening method helped in the identification of important acid resistance genes, thereby providing new insights into the mechanism underlying caries formation as well as in the prevention and treatment of early childhood caries (ECC). | 2018 | 29503702 |
| 6325 | 7 | 0.9997 | Repressed multidrug resistance genes in Streptomyces lividans. Multidrug resistance (MDR) systems are ubiquitously present in prokaryotes and eukaryotes and defend both types of organisms against toxic compounds in the environment. Four families of MDR systems have been described, each family removing a broad spectrum of compounds by a specific membrane-bound active efflux pump. In the present study, at least four MDR systems were identified genetically in the soil bacterium Streptomyces lividans. The resistance genes of three of these systems were cloned and sequenced. Two of them are accompanied by a repressor gene. These MDR gene sequences are found in most other Streptomyces species investigated. Unlike the constitutively expressed MDR genes in Escherichia coli and other gram-negative bacteria, all of the Streptomyces genes were repressed under laboratory conditions, and resistance arose by mutations in the repressor genes. | 2003 | 12937892 |
| 4380 | 8 | 0.9997 | Comparative genome analysis of ciprofloxacin-resistant Pseudomonas aeruginosa reveals genes within newly identified high variability regions associated with drug resistance development. The alarming rise of ciprofloxacin-resistant Pseudomonas aeruginosa has been reported in several clinical studies. Though the mutation of resistance genes and their role in drug resistance has been researched, the process by which the bacterium acquires high-level resistance is still not well understood. How does the genomic evolution of P. aeruginosa affect resistance development? Could the exposure of antibiotics to the bacteria enrich genomic variants that lead to the development of resistance, and if so, how are these variants distributed through the genome? To answer these questions, we performed 454 pyrosequencing and a whole genome analysis both before and after exposure to ciprofloxacin. The comparative sequence data revealed 93 unique resistance strain variation sites, which included a mutation in the DNA gyrase subunit A gene. We generated variation-distribution maps comparing the wild and resistant types, and isolated 19 candidates from three discrete resistance-associated high variability regions that had available transposon mutants, to perform a ciprofloxacin exposure assay. Of these region candidates with transposon disruptions, 79% (15/19) showed a reduction in the ability to gain high-level resistance, suggesting that genes within these high variability regions might enrich for certain functions associated with resistance development. | 2013 | 23808957 |
| 8456 | 9 | 0.9997 | Identification of genes required by Bacillus thuringiensis for survival in soil by transposon-directed insertion site sequencing. Transposon-directed insertion site sequencing was used to identify genes required by Bacillus thuringiensis to survive in non-axenic plant/soil microcosms. A total of 516 genetic loci fulfilled the criteria as conferring survival characteristics. Of these, 127 (24.6 %) were associated with uptake and transport systems; 227 loci (44.0 %) coded for enzymatic properties; 49 (9.5 %) were gene regulation or sensory loci; 40 (7.8 %) were structural proteins found in the cell envelope or had enzymatic activities related to it and 24 (4.7 %) were involved in the production of antibiotics or resistance to them. Eighty-three (16.1 %) encoded hypothetical proteins or those of unknown function. The ability to form spores was a key survival characteristic in the microcosms: bacteria, inoculated in either spore or vegetative form, were able to multiply and colonise the soil, whereas a sporulation-deficient mutant was not. The presence of grass seedlings was critical to colonisation. Bacteria labelled with green fluorescent protein were observed to adhere to plant roots. The sporulation-specific promoter of spo0A, the key regulator of sporulation, was strongly activated in the rhizosphere. In contrast, the vegetative-specific promoters of spo0A and PlcR, a pleiotropic regulator of genes with diverse activities, were only very weakly activated. | 2014 | 24310935 |
| 256 | 10 | 0.9997 | Antibiotic preparations contain DNA: a source of drug resistance genes? Fluorescence measurements and polymerase chain reaction amplification of streptomycete 16S ribosomal DNA sequences were used to show that a number of antibiotic preparations employed for human and animal use are contaminated with chromosomal DNA of the antibiotic-producing organism. The DNA contains identifiable antibiotic resistance gene sequences; the uptake of this DNA by bacteria and its functional incorporation into bacterial replicons would lead to the generation of antibiotic resistance determinants. We propose that the presence of DNA encoding drug resistance in antibiotic preparations has been a factor in the rapid development of multiple antibiotic resistance in bacteria. | 1993 | 8285621 |
| 8385 | 11 | 0.9997 | Function and Phylogeny of Bacterial Butyryl Coenzyme A:Acetate Transferases and Their Diversity in the Proximal Colon of Swine. Studying the host-associated butyrate-producing bacterial community is important, because butyrate is essential for colonic homeostasis and gut health. Previous research has identified the butyryl coenzyme A (CoA):acetate-CoA transferase (EC 2.3.8.3) as a gene of primary importance for butyrate production in intestinal ecosystems; however, this gene family (but) remains poorly defined. We developed tools for the analysis of butyrate-producing bacteria based on 12 putative but genes identified in the genomes of nine butyrate-producing bacteria obtained from the swine intestinal tract. Functional analyses revealed that eight of these genes had strong But enzyme activity. When but paralogues were found within a genome, only one gene per genome encoded strong activity, with the exception of one strain in which no gene encoded strong But activity. Degenerate primers were designed to amplify the functional but genes and were tested by amplifying environmental but sequences from DNA and RNA extracted from swine colonic contents. The results show diverse but sequences from swine-associated butyrate-producing bacteria, most of which clustered near functionally confirmed sequences. Here, we describe tools and a framework that allow the bacterial butyrate-producing community to be profiled in the context of animal health and disease. IMPORTANCE: Butyrate is a compound produced by the microbiota in the intestinal tracts of animals. This compound is of critical importance for intestinal health, and yet studying its production by diverse intestinal bacteria is technically challenging. Here, we present an additional way to study the butyrate-producing community of bacteria using one degenerate primer set that selectively targets genes experimentally demonstrated to encode butyrate production. This work will enable researchers to more easily study this very important bacterial function that has implications for host health and resistance to disease. | 2016 | 27613689 |
| 9326 | 12 | 0.9997 | Genes that enhance the ecological fitness of Shewanella oneidensis MR-1 in sediments reveal the value of antibiotic resistance. Environmental bacteria persist in various habitats, yet little is known about the genes that contribute to growth and survival in their respective ecological niches. Signature-tagged mutagenesis (STM) of Shewanella oneidensis MR-1 coupled with a screen involving incubations of mutant strains in anoxic aquifer sediments allowed us to identify 47 genes that enhance fitness in sediments. Gene functions inferred from annotations provide us with insight into physiological and ecological processes that environmental bacteria use while growing in sediment ecosystems. Identification of the mexF gene and other potential membrane efflux components by STM demonstrated that homologues of multidrug resistance genes present in pathogens are required for sediment fitness of nonpathogenic bacteria. Further studies with a mexF deletion mutant demonstrated that the multidrug resistance pump encoded by mexF is required for resistance to antibiotics, including chloramphenicol and tetracycline. Chloramphenicol-adapted cultures exhibited mutations in the gene encoding a TetR family regulatory protein, indicating a role for this protein in regulating expression of the mexEF operon. The relative importance of mexF for sediment fitness suggests that antibiotic efflux may be a required process for bacteria living in sediment systems. | 2007 | 17114320 |
| 4509 | 13 | 0.9997 | Distribution of triclosan-resistant genes in major pathogenic microorganisms revealed by metagenome and genome-wide analysis. The substantial use of triclosan (TCS) has been aimed to kill pathogenic bacteria, but TCS resistance seems to be prevalent in microbial species and limited knowledge exists about TCS resistance determinants in a majority of pathogenic bacteria. We aimed to evaluate the distribution of TCS resistance determinants in major pathogenic bacteria (N = 231) and to assess the enrichment of potentially pathogenic genera in TCS contaminated environments. A TCS-resistant gene (TRG) database was constructed and experimentally validated to predict TCS resistance in major pathogenic bacteria. Genome-wide in silico analysis was performed to define the distribution of TCS-resistant determinants in major pathogens. Microbiome analysis of TCS contaminated soil samples was also performed to investigate the abundance of TCS-resistant pathogens. We experimentally confirmed that TCS resistance could be accurately predicted using genome-wide in silico analysis against TRG database. Predicted TCS resistant phenotypes were observed in all of the tested bacterial strains (N = 17), and heterologous expression of selected TCS resistant genes from those strains conferred expected levels of TCS resistance in an alternative host Escherichia coli. Moreover, genome-wide analysis revealed that potential TCS resistance determinants were abundant among the majority of human-associated pathogens (79%) and soil-borne plant pathogenic bacteria (98%). These included a variety of enoyl-acyl carrier protein reductase (ENRs) homologues, AcrB efflux pumps, and ENR substitutions. FabI ENR, which is the only known effective target for TCS, was either co-localized with other TCS resistance determinants or had TCS resistance-associated substitutions. Furthermore, microbiome analysis revealed that pathogenic genera with intrinsic TCS-resistant determinants exist in TCS contaminated environments. We conclude that TCS may not be as effective against the majority of bacterial pathogens as previously presumed. Further, the excessive use of this biocide in natural environments may selectively enrich for not only TCS-resistant bacterial pathogens, but possibly for additional resistance to multiple antibiotics. | 2018 | 29420585 |
| 6109 | 14 | 0.9997 | Studies on arsenic transforming groundwater bacteria and their role in arsenic release from subsurface sediment. Ten different Gram-negative arsenic (As)-resistant and As-transforming bacteria isolated from As-rich groundwater of West Bengal were characterized to assess their role in As mobilization. 16S rRNA gene analysis confirmed the affiliation of these bacteria to genera Achromobacter, Brevundimonas, Rhizobium, Ochrobactrum, and Pseudoxanthomonas. Along with superior As-resistance and As-transformation abilities, the isolates showed broad metabolic capacity in terms of utilizing a variety of electron donors and acceptors (including As) under aerobic and anaerobic conditions, respectively. Arsenic transformation studies performed under various conditions indicated highly efficient As(3+) oxidation or As(5+) reduction kinetics. Genes encoding As(3+) oxidase (aioA), cytosolic As(5+) reductase (arsC), and As(3+) efflux pump (arsB and acr3) were detected within the test isolates. Sequence analyses suggested that As homeostasis genes (particularly arsC, arsB, and acr3) were acquired by most of the bacteria through horizontal gene transfer. A strong correlation between As resistance phenotype and the presence of As(3+) transporter genes was observed. Microcosm study showed that bacterial strain having cytosolic As(5+) reductase property could play important role in mobilizing As (as As(3+)) from subsurface sediment. | 2014 | 24764001 |
| 4454 | 15 | 0.9997 | Functional verification of computationally predicted qnr genes. BACKGROUND: The quinolone resistance (qnr) genes are widely distributed among bacteria. We recently developed and applied probabilistic models to identify tentative novel qnr genes in large public collections of DNA sequence data including fragmented metagenomes. FINDINGS: By using inducible recombinant expressions systems the functionality of four identified qnr candidates were evaluated in Escherichia coli. Expression of several known qnr genes as well as two novel candidates provided fluoroquinolone resistance that increased with elevated inducer concentrations. The two novel, functionally verified qnr genes are termed Vfuqnr and assembled qnr 1. Co-expression of two qnr genes suggested non-synergistic action. CONCLUSION: The combination of a computational model and recombinant expression systems provides opportunities to explore and identify novel antibiotic resistance genes in both genomic and metagenomic datasets. | 2013 | 24257207 |
| 8382 | 16 | 0.9997 | Transcriptional and Functional Analysis of Bifidobacterium animalis subsp. lactis Exposure to Tetracycline. Commercial probiotic bacteria must be tested for acquired antibiotic resistance elements to avoid potential transfer to pathogens. The European Food Safety Authority recommends testing resistance using microdilution culture techniques previously used to establish inhibitory thresholds for the Bifidobacterium genus. Many Bifidobacterium animalis subsp. lactis strains exhibit increased resistance to tetracycline, historically attributed to the ribosomal protection gene tet(W). However, some strains that harbor genetically identical tet(W) genes show various inhibition levels, suggesting that other genetic elements also contribute to observed differences. Here, we adapted several molecular assays to confirm the inhibition of B. animalis subsp. lactis strains Bl-04 and HN019 and employed RNA sequencing to assess the transcriptional differences related to genomic polymorphisms. We detected specific stress responses to the antibiotic by correlating ATP concentration to number of viable genome copies from droplet digital PCR and found that the bacteria were still metabolically active in high drug concentrations. Transcriptional analyses revealed that several polymorphic regions, particularly a novel multidrug efflux transporter, were differentially expressed between the strains in each experimental condition, likely having phenotypic effects. We also found that the tet(W) gene was upregulated only during subinhibitory tetracycline concentrations, while two novel tetracycline resistance genes were upregulated at high concentrations. Furthermore, many genes involved in amino acid metabolism and transporter function were upregulated, while genes for complex carbohydrate utilization, protein metabolism, and clustered regularly interspaced short palindromic repeat(s) (CRISPR)-Cas systems were downregulated. These results provide high-throughput means for assessing antibiotic resistances of two highly related probiotic strains and determine the genetic network that contributes to the global tetracycline response.IMPORTANCEBifidobacterium animalis subsp. lactis is widely used in human food and dietary supplements. Although well documented to be safe, B. animalis subsp. lactis strains must not contain transferable antibiotic resistance elements. Many B. animalis subsp. lactis strains have different resistance measurements despite being genetically similar, and the reasons for this are not well understood. In the current study, we sought to examine how genomic differences between two closely related industrial B. animalis subsp. lactis strains contribute to different resistance levels. This will lead to a better understanding of resistance, identify future targets for analysis of transferability, and expand our understanding of tetracycline resistance in bacteria. | 2018 | 30266728 |
| 6335 | 17 | 0.9997 | Gene Amplification Uncovers Large Previously Unrecognized Cryptic Antibiotic Resistance Potential in E. coli. The activation of unrecognized antibiotic resistance genes in the bacterial cell can give rise to antibiotic resistance without the need for major mutations or horizontal gene transfer. We hypothesize that bacteria harbor an extensive array of diverse cryptic genes that can be activated in response to antibiotics via adaptive resistance. To test this hypothesis, we developed a plasmid assay to randomly manipulate gene copy numbers in Escherichia coli cells and identify genes that conferred resistance when amplified. We then tested for cryptic resistance to 18 antibiotics and identified genes conferring resistance. E. coli could become resistant to 50% of the antibiotics tested, including chloramphenicol, d-cycloserine, polymyxin B, and 6 beta-lactam antibiotics, following this manipulation. Known antibiotic resistance genes comprised 13% of the total identified genes, where 87% were unclassified (cryptic) antibiotic resistance genes. These unclassified genes encoded cell membrane proteins, stress response/DNA repair proteins, transporters, and miscellaneous or hypothetical proteins. Stress response/DNA repair genes have a broad antibiotic resistance potential, as this gene class, in aggregate, conferred cryptic resistance to nearly all resistance-positive antibiotics. We found that antibiotics that are hydrophilic, those that are amphipathic, and those that inhibit the cytoplasmic membrane or cell wall biosynthesis were more likely to induce cryptic resistance in E. coli. This study reveals a diversity of cryptic genes that confer an antibiotic resistance phenotype when present in high copy number. Thus, our assay can identify potential novel resistance genes while also describing which antibiotics are prone to induce cryptic antibiotic resistance in E. coli. IMPORTANCE Predicting where new antibiotic resistance genes will rise is a challenge and is especially important when new antibiotics are developed. Adaptive resistance allows sensitive bacterial cells to become transiently resistant to antibiotics. This provides an opportune time for cells to develop more efficient resistance mechanisms, such as tolerance and permanent resistance to higher antibiotic concentrations. The biochemical diversity harbored within bacterial genomes may lead to the presence of genes that could confer resistance when timely activated. Therefore, it is crucial to understand adaptive resistance to identify potential resistance genes and prolong antibiotics. Here, we investigate cryptic resistance, an adaptive resistance mechanism, and identify unknown (cryptic) antibiotic resistance genes that confer resistance when amplified in a laboratory strain of E. coli. We also pinpoint antibiotic characteristics that are likely to induce cryptic resistance. This study may help detect novel antibiotic resistance genes and provide the foundation to help develop more effective antibiotics. | 2021 | 34756069 |
| 175 | 18 | 0.9996 | The acquired pco gene cluster in Salmonella enterica mediates resistance to copper. The pervasive environmental metal contamination has led to selection of heavy-metal resistance genes in bacteria. The pco and sil clusters are located on a mobile genetic element and linked to heavy-metal resistance. These clusters have been found in Salmonella enterica serovars isolated from human clinical cases and foods of animal origin. This may be due to the use of heavy metals, such as copper, in animal feed for their antimicrobial and growth promotion properties. The sil cluster can be found alone or in combination with pco cluster, either in the chromosome or on a plasmid. Previous reports have indicated that sil, but not pco, cluster contributes to copper resistance in S. enterica Typhimurium. However, the role of the pco cluster on the physiology of non-typhoidal S. enterica remains poorly understood. To understand the function of the pco gene cluster, a deletion mutant of pcoABCD genes was constructed using allelic exchange mutagenesis. Deletion of pcoABCD genes inhibited growth of S. enterica in high-copper medium, but only under anaerobic environment. Complementation of the mutant reversed the growth phenotype. The survival of S. enterica in RAW264.7 macrophages was not affected by the loss of pcoABCD genes. This study indicates that the acquired pco cluster is crucial for copper detoxification in S. enterica, but it is not essential for intracellular replication within macrophages. | 2024 | 39290517 |
| 4508 | 19 | 0.9996 | Tetracycline Resistance Genes Identified from Distinct Soil Environments in China by Functional Metagenomics. Soil microbiota represents one of the ancient evolutionary origins of antibiotic resistance and has been increasingly recognized as a potentially vast unstudied reservoir of resistance genes with possibilities to exchange with pathogens. Tetracycline resistance is one of the most abundant antibiotic resistances that may transfer among clinical and commensal microorganisms. To investigate tetracycline resistance genes from soil bacteria in different habitats, we performed functional analysis of three metagenomic libraries derived from soil samples collected from Yunnan, Sichuan, and Tibet, respectively, in China. We found efflux transporter genes form all the libraries, including 21 major facilitator superfamily efflux pump genes and one multidrug and toxic compound extrusion (MATE) transporter gene. Interestingly, we also identified two tetracycline destructase genes, belonging to a newly described family of tetracycline-inactivating enzymes that scarcely observed in clinical pathogens, from the Tibet library. The inactivation activity of the putative enzyme was confirmed in vitro by biochemical analysis. Our results indicated that efflux pumps distributed predominantly across habitats. Meanwhile, the mechanism of enzymatic inactivation for tetracycline resistance should not be neglected and merits further investigation. | 2017 | 28790997 |