Plasmid最新文献

{"title":"Characterization of blaCMY-2-carrying IncC and rmtB-carrying IncI1/ST136 plasmids in an avian Escherichia coli ST224 strain","authors":"Dan-Dan He ,&nbsp;Meng-Mei Cui ,&nbsp;Teng-Li Zhang,&nbsp;Gong-Zheng Hu,&nbsp;Jian-Hua Liu,&nbsp;Yu-Shan Pan","doi":"10.1016/j.plasmid.2021.102555","DOIUrl":"https://doi.org/10.1016/j.plasmid.2021.102555","url":null,"abstract":"<div><p>To analyze characteristics and underlying evolutionary processes of IncC and IncI1 plasmids in a multidrug-resistant avian <em>E. coli</em><span> strain, antibiotic susceptibility<span> testing, PCR, conjugation assays, and next-generation sequencing were performed. The type 1 IncC plasmid pEC009.1 harbored three antimicrobial resistance regions including IS</span></span><em>Ecp1</em>-<em>bla</em>_CMY-2-<em>blc</em>-<em>sugE</em><span><span>, ARI-B resistance island, and ARI-A island that was a mosaic multidrug resistance region (MRR) comprised of a class 1 </span>integron with cassette array |</span><em>aac</em>(6′)<em>-II</em>(<em>aacA7</em>)|<em>qacE∆1</em>|<em>sul1</em>|, IS<em>26</em>-<em>mphR</em>(A)-<em>mrx</em>-<em>mph</em>(A)-IS<em>26</em>, IS<em>26</em>-<em>fosA3</em>-IS<em>26</em>, and mercury resistance cluster <em>merRTPABDE</em>. It is the first report of three different size circular forms derived from IS<em>26</em>-<em>mphR</em>(A)-<em>mrx</em>-<em>mph</em>(A)-IS<em>26</em>-<em>fosA3</em>-IS<em>26</em><span> in ARI-A of type 1 IncC plasmid. In IncI1/ST136 pEC009.2, the truncated transposon Tn</span><em>1722</em> carrying <em>bla</em>_TEM-1b, <em>rmtB</em>, <em>aac(3)-IId</em>(<em>aacC2d</em>), and a class 1 integron with cassette array |<em>dfrA12</em>|orfF|<em>aadA2</em><span>|, inserted into the plasmid backbone generating 5-bp direct repeats (DRs, TATAA) at the boundaries of the region, which was highly similar to that of other IncI1 plasmids, and differed by the arrangements of resistance determinants. Comparison among two epidemic plasmid lineages showed complex MRRs respectively located in the specific position in type 1 IncC and IncI1/ST136 plasmids with conserved backbones, and these have evolved via multiple events involved in mobile elements-mediated loss and gain of resistance genes and accessory genes. Strains harboring these plasmids may serve as a reservoir for antibiotic resistance genes, thereby contributing to the rapid spread of resistance genes and posing a public health threat.</span></p></div>","PeriodicalId":49689,"journal":{"name":"Plasmid","volume":"114 ","pages":"Article 102555"},"PeriodicalIF":2.6,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.plasmid.2021.102555","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72204814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mobile genetic elements beyond the VanB-resistance dissemination among hospital-associated enterococci and other Gram-positive bacteria","authors":"Ewa Sadowy","doi":"10.1016/j.plasmid.2021.102558","DOIUrl":"10.1016/j.plasmid.2021.102558","url":null,"abstract":"<div><p>An increasing resistance to vancomycin among clinically relevant enterococci, such as <em>Enterococcus faecalis</em> and <em>Enterococcus faecium</em> is a cause of a great concern, as it seriously limits treatment options. The <em>vanB</em> operon is one of most common determinants of this type of resistance. Genes constituting the operon are located in conjugative transposons, such as Tn<em>1549</em>-type transposons or, more rarely, in ICE<em>Efa</em>V583-type structures. Such elements show differences in structure and size, and reside in various sites of bacterial chromosome or, in the case of Tn<em>1549</em>-type transposons, are also occasionally associated with plasmids of divergent replicon types. While conjugative transposition contributes to the acquisition of Tn<em>1549</em>-type transposons from anaerobic gut commensals by enterococci, chromosomal recombination and conjugal transfer of plasmids appear to represent main mechanisms responsible for horizontal dissemination of <em>vanB</em> determinants among hospital <em>E. faecalis</em> and <em>E. faecium</em>.</p><p>This review focuses on diversity of genetic elements harbouring <em>vanB</em> determinants in hospital-associated strains of <em>E. faecium</em> and <em>E. faecalis,</em> the mechanisms beyond <em>vanB</em> spread in populations of these bacteria, and provides an overview of the <em>vanB-</em>MGE distribution among other enterococci and Gram-positive bacteria as potential reservoirs of <em>vanB</em> genes.</p></div>","PeriodicalId":49689,"journal":{"name":"Plasmid","volume":"114 ","pages":"Article 102558"},"PeriodicalIF":2.6,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.plasmid.2021.102558","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38840204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Functional analysis of the catalytic triad of the hAT-family transposase TcBuster","authors":"Lauren E. Woodard ,&nbsp;Felisha M. Williams ,&nbsp;Isria C. Jarrett ,&nbsp;Matthew H. Wilson","doi":"10.1016/j.plasmid.2021.102554","DOIUrl":"10.1016/j.plasmid.2021.102554","url":null,"abstract":"<div><p><em>TcBuster</em> is a <em>hAT</em><span>-family DNA transposon<span> from the red flour beetle, </span></span><em>Tribolium castaneum.</em> The <em>TcBuster</em><span><span> transposase is of interest for genome engineering as it is highly active in insect and </span>mammalian cells<span>. To test the predicted catalytic triad of </span></span><em>TcBuster</em>, each residue of the catalytic triad of a haemagglutinin-tagged <em>TcBuster</em><span> transposase was individually mutated to a structurally conserved amino acid. Using a drug-resistant colony assay for transposon integration, we found that the D223N, D289N, and E589Q mutants of </span><em>TcBuster</em> transposase were inactive in human cells. We used a modified chromatin immunoprecipitation assay to determine that each mutant maintained binding to <em>TcBuster</em> transposon inverted repeat elements. Although the catalytic mutants retained their transposon binding properties, mutants displayed altered expression and localization in human cells. None of the catalytic mutants formed characteristic <em>TcBuster</em><span> transposase rodlet structures, and the D223N and D289N mutants were not able to be detected by immunofluorescence microscopy. Immunoblot analysis demonstrated that the E589Q mutant is less abundant than wild-type </span><em>TcBuster</em> transposase. Cells transfected with either <em>TcBuster</em> or <em>TcBuster</em>-E589Q transposase were imaged by structured illumination microscopy to quantify differences in the length of the transposase rodlets. The average length of the <em>TcBuster</em> transposase rodlets (<em>N</em> = 39) was 3.284 μm while the E589Q rodlets (<em>N</em> = 33) averaged 1.157 μm (<em>p</em> &lt; 0.0001; <em>t</em><span>-test). The catalytic triad mutations decreased overall protein levels and disrupted transposase rodlet formation while nuclear localization and DNA binding to the inverted repeat elements were maintained. Our results may have broader implications for the overproduction inhibition phenomenon observed for DNA transposons.</span></p></div>","PeriodicalId":49689,"journal":{"name":"Plasmid","volume":"114 ","pages":"Article 102554"},"PeriodicalIF":2.6,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.plasmid.2021.102554","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38778858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insights into the individual evolutionary origins of Yersinia virulence factor effector proteins","authors":"Veronica R. Moorman ,&nbsp;James I. Cohen","doi":"10.1016/j.plasmid.2021.102562","DOIUrl":"10.1016/j.plasmid.2021.102562","url":null,"abstract":"<div><p>Pathogenic <span><em>Yersinia</em></span> bacteria, including <em>Y. pseudotubuclosis Y. enterocolitica</em>, and <em>Y. pestis</em><span>, contain the mosaic plasmid pYV that encodes for, among other things, a number of proteinaceous virulence factors<span>. While the evolutionary histories of many of the biovars and strains of pathogenic </span></span><em>Yersinia</em> species are well documented, the origins of many of the individual virulence factors have not been comprehensively examined. Here, the evolutionary origins of the genes coding for a set of <em>Yersinia</em><span> outer protein (Yop) virulence factors were investigated through phylogenetic reconstruction and subsequence analysis. It was found that many of these genes had only a few sequenced homologs and none of the resolved phylogenies recovered the same relationships as was resolved from chromosomal analyses. Many of the evolutionary relationships differ greatly among genes on the plasmid, and variation is also found across different domains of the same gene, which provides evidence of the mosaic nature of the plasmid as well as multiple genes on the plasmid. This mosaic aspect also relates to patterns of selection, which vary among the studied domains.</span></p></div>","PeriodicalId":49689,"journal":{"name":"Plasmid","volume":"114 ","pages":"Article 102562"},"PeriodicalIF":2.6,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.plasmid.2021.102562","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38782452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The ever-expanding tcp conjugation locus of pCW3 from Clostridium perfringens","authors":"Sarah A. Revitt-Mills,&nbsp;Thomas D. Watts,&nbsp;Dena Lyras,&nbsp;Vicki Adams,&nbsp;Julian I. Rood","doi":"10.1016/j.plasmid.2020.102516","DOIUrl":"10.1016/j.plasmid.2020.102516","url":null,"abstract":"<div><p>The spore-forming, anaerobic Gram positive pathogen <span><em>Clostridium perfringens</em></span><span> encodes many of its disease-causing toxins on closely related conjugative plasmids<span>. Studies of the tetracycline resistance plasmid pCW3 have identified many of the genes involved in conjugative transfer, which are located in the </span></span><em>tcp</em> conjugation locus. Upstream of this locus is an uncharacterised region (the <em>cnaC</em> region) that is highly conserved. This study examined the importance in pCW3 conjugation of several highly conserved proteins encoded in the <em>cnaC</em> region. Conjugative mating studies suggested that the SrtD, TcpN and Dam proteins were required for efficient pCW3 transfer between <em>C. perfringens</em> cells from the same strain background. The requirement of these proteins for conjugation was amplified in matings between <em>C. perfringens</em> cells of different strain backgrounds. Additionally, the putative collagen adhesin protein, CnaC, was only required for the optimal transfer of pCW3 between cells of different strain backgrounds. Based on these studies we postulate that CnaC, SrtD, TcpN and Dam are involved in enhancing the transfer frequency of pCW3. These studies have led to a significant expansion of the <em>tcp</em> conjugation locus, which now encompasses a 19 kb region.</p></div>","PeriodicalId":49689,"journal":{"name":"Plasmid","volume":"113 ","pages":"Article 102516"},"PeriodicalIF":2.6,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.plasmid.2020.102516","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38033447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution and dissemination of L and M plasmid lineages carrying antibiotic resistance genes in diverse Gram-negative bacteria","authors":"Grace A. Blackwell ,&nbsp;Emma L. Doughty ,&nbsp;Robert A. Moran","doi":"10.1016/j.plasmid.2020.102528","DOIUrl":"10.1016/j.plasmid.2020.102528","url":null,"abstract":"<div><p><span>Conjugative, broad host-range plasmids of the L/M complex have been associated with antibiotic resistance<span> since the 1970s. They are found in Gram-negative bacterial genera that cause human infections and persist in hospital environments. It is crucial that these plasmids are typed accurately so that their clinical and global dissemination can be traced in epidemiological studies. The L/M complex has previously been divided into L, M1 and M2 subtypes. However, those types do not encompass all diversity seen in the group. Here, we have examined 148 complete L/M plasmid sequences in order to understand the diversity of the complex and trace the evolution of distinct lineages. The backbone sequence of each plasmid was determined by removing translocatable genetic elements and reversing their effects </span></span><em>in silico</em><span>. The sequence identities of replication regions and complete backbones were then considered for typing. This supported the distinction of L and M plasmids and revealed that there are five L and eight M types, where each type is comprised of further sub-lineages that are distinguished by variation in their backbone and translocatable element content. Regions containing antibiotic resistance genes in L and M sub-lineages have often formed by initial rare insertion events, followed by insertion of other translocatable elements within the inceptive element. As such, islands evolve </span><em>in situ</em> to contain genes conferring resistance to multiple antibiotics. In some cases, different plasmid sub-lineages have acquired the same or related resistance genes independently. This highlights the importance of these plasmids in acting as vehicles for the dissemination of emerging resistance genes. Materials are provided here for typing plasmids of the L/M complex from complete sequences or draft genomes. This should enable rapid identification of novel types and facilitate tracking the evolution of existing lineages.</p></div>","PeriodicalId":49689,"journal":{"name":"Plasmid","volume":"113 ","pages":"Article 102528"},"PeriodicalIF":2.6,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.plasmid.2020.102528","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38261071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bacteriophages as sources of small non-coding RNA molecules","authors":"Sylwia Bloch ,&nbsp;Natalia Lewandowska ,&nbsp;Grzegorz Węgrzyn ,&nbsp;Bożena Nejman-Faleńczyk","doi":"10.1016/j.plasmid.2020.102527","DOIUrl":"10.1016/j.plasmid.2020.102527","url":null,"abstract":"<div><p>Bacteriophages play an essential role in the transferring of genes that contribute to the bacterial virulence and whose products are dangerous to human health. Interestingly, phages carrying virulence genes are mostly temperate and in contrast to lytic phages undergo both lysogenic and lytic cycles. Importantly, expression of the majority of phage genes and subsequent production of phage encoded proteins is suppressed during lysogeny. The expression of the majority of phage genes is tightly linked to lytic development. Among others, small non-coding RNAs (sRNAs) of phage origin are involved in the regulation of phage gene expression and thus play an important role in both phage and host development. In the case of bacteria, sRNAs affect processes such as virulence, colonization ability, motility and cell growth or death. In turn, in the case of phages, they play essential roles during the early stage of infection, maintaining the state of lysogeny and silencing the expression of late structural genes, thereby regulating the transition between phage life cycles. Interestingly, sRNAs have been identified in both lytic and temperate phages and they have been discussed in this work according to this classification. Particular attention was paid to viral sRNAs resembling eukaryotic microRNAs.</p></div>","PeriodicalId":49689,"journal":{"name":"Plasmid","volume":"113 ","pages":"Article 102527"},"PeriodicalIF":2.6,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.plasmid.2020.102527","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38250707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Incorporating the plasmidome into antibiotic resistance surveillance in animal agriculture","authors":"N. Ricker ,&nbsp;B.S. Spoja ,&nbsp;N. May ,&nbsp;G. Chalmers","doi":"10.1016/j.plasmid.2020.102529","DOIUrl":"10.1016/j.plasmid.2020.102529","url":null,"abstract":"<div><p>Mobile genetic elements (MGE) carrying resistance genes represent a unique challenge to risk assessment and surveillance of antimicrobial resistance (AMR). Yet determining the mobility of resistance genes within animal microbiomes is essential to evaluating the potential dissemination from livestock to potential human pathogens, as well as evaluating co-selection mechanisms that may impact persistence of resistance genes with changing antibiotic use patterns. Current surveillance efforts utilize phenotypic testing and sequencing of individual isolates for tracking of AMR in livestock. In this work, we investigated the utility of using long-read sequencing of the plasmids from mixed <em>Enterobacterales</em> enrichments of swine fecal samples as a surveillance strategy for AMR plasmids. Enrichments were performed in either MacConkey broth without selection or with selection by addition of tetracycline or ceftriaxone, and plasmids were extracted and sequenced in order to evaluate the diversity of plasmids enriched by each method. Intact resistance plasmids were successfully assembled, as well as complex resistance transposons carrying multiple repeated elements that would interfere with assembly by short read sequencing technologies. Comparison of the assembled plasmids with representatives from public databases confirmed the quality of the assemblies and also revealed the occurrence of IncI2 plasmids carrying <em>bla</em>_CMY-2 in Ontario swine samples, which have not been found in previous studies.</p></div>","PeriodicalId":49689,"journal":{"name":"Plasmid","volume":"113 ","pages":"Article 102529"},"PeriodicalIF":2.6,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.plasmid.2020.102529","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38245513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantifying plasmid dynamics using single-cell microfluidics and image bioinformatics","authors":"J.C.R. Hernandez-Beltran ,&nbsp;J. Rodríguez-Beltrán ,&nbsp;A. San Millán ,&nbsp;R. Peña-Miller ,&nbsp;A. Fuentes-Hernández","doi":"10.1016/j.plasmid.2020.102517","DOIUrl":"10.1016/j.plasmid.2020.102517","url":null,"abstract":"<div><p><span><span>Multicopy plasmids play an important role in bacterial ecology and evolution by accelerating the rate of adaptation and providing a platform for rapid gene amplification and evolutionary rescue. Despite the relevance of plasmids in bacterial evolutionary dynamics, evaluating the population-level consequences of randomly segregating and replicating plasmids in individual cells remains a challenging problem, both in theory and experimentally. In recent years, technological advances in </span>fluorescence microscopy and microfluidics have allowed studying temporal changes in gene expression by quantifying the fluorescent intensity of individual cells under controlled environmental conditions. In this paper, we will describe the manufacture, experimental setup, and data analysis pipeline of different microfluidic systems that can be used to study plasmid dynamics, both in single-cells and in populations. To illustrate the benefits and limitations of microfluidics to study multicopy plasmid dynamics, we will use an experimental model system consisting on </span><em>Escherichia coli</em> K12 carrying non-conjugative, multicopy plasmids (19 copies per cell, in average) encoding different fluorescent markers and <em>β</em>-lactam resistance genes. First, we will use an image-based flow cytometer to estimate changes in the allele distribution of a heterogeneous population under different selection regimes. Then we will use a mothermachine microfluidic device to obtain time-series of fluorescent intensity of individual cells to argue that plasmid segregation and replication dynamics are inherently stochastic processes. Finally, using a microchemostat, we track thousands of cells in time to reconstruct bacterial lineages and evaluate the allele frequency distributions that emerge in response to a range of selective pressures.</p></div>","PeriodicalId":49689,"journal":{"name":"Plasmid","volume":"113 ","pages":"Article 102517"},"PeriodicalIF":2.6,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.plasmid.2020.102517","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38041062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution of IS26-bounded pseudo-compound transposons carrying the tet(C) tetracycline resistance determinant","authors":"Carol H. Pong,&nbsp;Robert A. Moran ,&nbsp;Ruth M. Hall","doi":"10.1016/j.plasmid.2020.102541","DOIUrl":"10.1016/j.plasmid.2020.102541","url":null,"abstract":"<div><p>A large plasmid, pCERC14, found in an antibiotic resistant commensal <em>Escherichia coli</em><span> isolate recovered from a healthy adult was sequenced. pCERC14 was 162,926 bp and carried FII-18 and FIB-1 replicons and an F-like transfer region as well as several virulence determinants, some of which are involved in the uptake of iron which would be advantageous for the commensal lifestyle. The plasmid backbone is interrupted in 11 places by complete IS (IS</span><em>1</em> (4 copies), IS<em>2</em> (2), IS<em>629</em> (2) and single IS<em>100</em>, IS<em>186</em><span>, ISEc33) and in three places by partial IS copies. The antibiotic resistance genes were found in two IS</span><em>26</em><span><span>-bounded pseudo-compound transposons (PCT). One contained a remnant of a class 1 </span>integron that includes a </span><em>dfrA5</em><span> gene cassette and the </span><em>sul1</em><span><span> gene conferring resistance to trimethoprim and </span>sulphonamides, respectively. The second, named PTn</span><em>tet</em><span>(C)-var, contained a 4828 bp DNA segment that includes the </span><em>tet</em><span>(C) tetracycline resistance determinant. As </span><em>tet</em>(C) is relatively rare in <em>E. coli</em> and other Gram-negative bacterial isolates, the structure and evolution of <em>tet</em>(C)-containing PCT in available sequences was examined. The largest identified was PTn<em>tet</em>(C), a close relative of PTn<em>tet</em>(C)-var, and a potential progenitor for these PCT. Most PCT shared one internal boundary with PTn<em>tet</em>(C) but the length of the central <em>tet</em>(C)-containing segment was shorter due to IS<em>26</em>-mediated deletions. The most abundant variant form, previously named Tn<em>6309</em>, was widely distributed and, in a derivative of it, most of the <em>tetA</em>(C) gene has been replaced by the <em>tetA</em><span>(A) gene presumably by homologous recombination.</span></p></div>","PeriodicalId":49689,"journal":{"name":"Plasmid","volume":"112 ","pages":"Article 102541"},"PeriodicalIF":2.6,"publicationDate":"2020-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.plasmid.2020.102541","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38519114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}