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Genetic and phenotypic analyses of mcr-harboring extended-spectrum β-lactamase-producing Escherichia coli isolates from companion dogs and cats in Japan. Vet Microbiol 2023; 280:109695. [PMID: 36848815 DOI: 10.1016/j.vetmic.2023.109695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 01/17/2023] [Accepted: 02/15/2023] [Indexed: 02/18/2023]
Abstract
The emergence of mcr plasmid-mediated colistin-resistant extended-spectrum β-lactamase (ESBL)-producing Enterobacterales among companion dogs and cats poses a risk of the animals acting as reservoirs for cross-species transmission. However, current knowledge of mcr-harboring ESBL-producing Enterobacterales in companion dogs and cats is still limited; thus, the genetic and phenotypic characteristics of the bacterial isolates and plasmids, in companion dogs and cats, remain to be elucidated. Here, we identified mcr gene-harboring ESBL-producing Escherichia coli isolates during whole-genome sequencing of ESBL-producing E. coli isolates from a dog and a cat in Osaka, Japan. Colistin-resistant MY732 isolate from a dog carried two plasmids: mcr-1.1-harboring IncI2 plasmid and blaCTX-M-14-harboring IncFIB plasmid. Conjugation assays revealed that both plasmids can be co-transferred even though the IncFIB plasmid lacked a conjugal transfer gene cassette. The other isolate MY504 from a cat harbored two bla genes and mcr-9 on the identical IncHI2 plasmid. This isolate was not resistant to colistin, which is likely to be due to deletion of the regulatory two-component QseBC system associated with the mcr-9 expression. To the best of our knowledge, this is the first report of a colistin-resistant ESBL-producing E. coli isolate harboring mcr-1 from a companion dog in Japan. Given that the mcr gene-harboring IncI2 and IncHI2 plasmids in this study shared high homology with plasmids from human or animal-derived Enterobacterales, companion dogs and cats may act as important reservoirs for cross-species transmission of the mcr gene in the community, in Japan.
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Evans DR, Griffith MP, Sundermann AJ, Shutt KA, Saul MI, Mustapha MM, Marsh JW, Cooper VS, Harrison LH, Van Tyne D. Systematic detection of horizontal gene transfer across genera among multidrug-resistant bacteria in a single hospital. eLife 2020; 9:53886. [PMID: 32285801 PMCID: PMC7156236 DOI: 10.7554/elife.53886] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Accepted: 03/14/2020] [Indexed: 12/16/2022] Open
Abstract
Multidrug-resistant bacteria pose a serious health threat, especially in hospitals. Horizontal gene transfer (HGT) of mobile genetic elements (MGEs) facilitates the spread of antibiotic resistance, virulence, and environmental persistence genes between nosocomial pathogens. We screened the genomes of 2173 bacterial isolates from healthcare-associated infections from a single hospital over 18 months, and identified identical nucleotide regions in bacteria belonging to distinct genera. To further resolve these shared sequences, we performed long-read sequencing on a subset of isolates and generated highly contiguous genomes. We then tracked the appearance of ten different plasmids in all 2173 genomes, and found evidence of plasmid transfer independent from bacterial transmission. Finally, we identified two instances of likely plasmid transfer within individual patients, including one plasmid that likely transferred to a second patient. This work expands our understanding of HGT in healthcare settings, and can inform efforts to limit the spread of drug-resistant pathogens in hospitals.
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Affiliation(s)
- Daniel R Evans
- Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, United States.,Department of Infectious Diseases and Microbiology, University of Pittsburgh Graduate School of Public Health, Pittsburgh, United States
| | - Marissa P Griffith
- Microbial Genomic Epidemiology Laboratory, Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, United States
| | - Alexander J Sundermann
- Microbial Genomic Epidemiology Laboratory, Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, United States
| | - Kathleen A Shutt
- Microbial Genomic Epidemiology Laboratory, Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, United States
| | - Melissa I Saul
- Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, United States
| | - Mustapha M Mustapha
- Microbial Genomic Epidemiology Laboratory, Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, United States
| | - Jane W Marsh
- Microbial Genomic Epidemiology Laboratory, Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, United States
| | - Vaughn S Cooper
- Department of Microbiology and Molecular Genetics, and Center for Evolutionary Biology and Medicine, University of Pittsburgh, Pittsburgh, United States
| | - Lee H Harrison
- Microbial Genomic Epidemiology Laboratory, Infectious Diseases Epidemiology Research Unit, University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, United States
| | - Daria Van Tyne
- Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, United States
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Sekizuka T, Kawanishi M, Ohnishi M, Shima A, Kato K, Yamashita A, Matsui M, Suzuki S, Kuroda M. Elucidation of quantitative structural diversity of remarkable rearrangement regions, shufflons, in IncI2 plasmids. Sci Rep 2017; 7:928. [PMID: 28424528 PMCID: PMC5430464 DOI: 10.1038/s41598-017-01082-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 03/20/2017] [Indexed: 12/30/2022] Open
Abstract
A multiple DNA inversion system, the shufflon, exists in incompatibility (Inc) I1 and I2 plasmids. The shufflon generates variants of the PilV protein, a minor component of the thin pilus. The shufflon is one of the most difficult regions for de novo genome assembly because of its structural diversity even in an isolated bacterial clone. We determined complete genome sequences, including those of IncI2 plasmids carrying mcr-1, of three Escherichia coli strains using single-molecule, real-time (SMRT) sequencing and Illumina sequencing. The sequences assembled using only SMRT sequencing contained misassembled regions in the shufflon. A hybrid analysis using SMRT and Illumina sequencing resolved the misassembled region and revealed that the three IncI2 plasmids, excluding the shufflon region, were highly conserved. Moreover, the abundance ratio of whole-shufflon structures could be determined by quantitative structural variation analysis of the SMRT data, suggesting that a remarkable heterogeneity of whole-shufflon structural variations exists in IncI2 plasmids. These findings indicate that remarkable rearrangement regions should be validated using both long-read and short-read sequencing data and that the structural variation of PilV in the shufflon might be closely related to phenotypic heterogeneity of plasmid-mediated transconjugation involved in horizontal gene transfer even in bacterial clonal populations.
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Affiliation(s)
- Tsuyoshi Sekizuka
- Pathogen Genomics Center, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjyuku-ku, Tokyo, 162-8640, Japan.
| | - Michiko Kawanishi
- Assay Division II, Bacterial Assay Section, National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1-15-1 Tokura, Kokubunji-shi, 185-8511, Tokyo, Japan
| | - Mamoru Ohnishi
- Ohnishi Laboratory of Veterinary Microbiology, 10-3-3 Nishirokujyouminami, Shibetsugunnakashibetsu-cho, 086-1106, Hokkaido, Japan
| | - Ayaka Shima
- Department of Bacteriology II, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashimurayama-shi, Tokyo, 208-0011, Japan
| | - Kengo Kato
- Pathogen Genomics Center, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjyuku-ku, Tokyo, 162-8640, Japan
| | - Akifumi Yamashita
- Pathogen Genomics Center, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjyuku-ku, Tokyo, 162-8640, Japan
| | - Mari Matsui
- Department of Bacteriology II, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashimurayama-shi, Tokyo, 208-0011, Japan
| | - Satowa Suzuki
- Department of Bacteriology II, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashimurayama-shi, Tokyo, 208-0011, Japan
| | - Makoto Kuroda
- Pathogen Genomics Center, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjyuku-ku, Tokyo, 162-8640, Japan
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Whole-Genome Sequencing Identifies In Vivo Acquisition of a blaCTX-M-27-Carrying IncFII Transmissible Plasmid as the Cause of Ceftriaxone Treatment Failure for an Invasive Salmonella enterica Serovar Typhimurium Infection. Antimicrob Agents Chemother 2016; 60:7224-7235. [PMID: 27671066 DOI: 10.1128/aac.01649-16] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 09/12/2016] [Indexed: 12/11/2022] Open
Abstract
We report a case of ceftriaxone treatment failure for bacteremia caused by Salmonella enterica subsp. enterica serovar Typhimurium, due to the in vivo acquisition of a blaCTX-M-27-encoding IncFII group transmissible plasmid. The original β-lactamase-susceptible isolate ST882S was replaced by the resistant isolate ST931R during ceftriaxone treatment. After relapse, treatment was changed to ciprofloxacin, and the patient recovered. Isolate ST931R could transfer resistance to Escherichia coli at 37°C. We used whole-genome sequencing of ST882S and ST931R, the E. coli transconjugant, and isolated plasmid DNA to unequivocally show that ST882S and ST931R had identical chromosomes, both having 206 identical single-nucleotide polymorphisms (SNPs) versus S Typhimurium 14028s. We assembled a complete circular genome for ST931R, to which ST882S reads mapped with no SNPs. ST882S and ST931R were isogenic except for the presence of three additional plasmids in ST931R. ST931R and the E. coli transconjugant were ceftriaxone resistant due to the presence of a 60.5-kb IS26-flanked, blaCTX-M-27-encoding IncFII plasmid. Compared to 14082s, ST931R has almost identical Gifsy-1, Gifsy-2, and ST64B prophages, lacks Gifsy-3, and instead carries a unique Fels-2 prophage related to that found in LT2. ST882S and ST931R both had a 94-kb virulence plasmid showing >99% identity with pSLT14028s and a cryptic 3,904-bp replicon; ST931R also has cryptic 93-kb IncI1 and 62-kb IncI2 group plasmids. To the best of our knowledge, in vivo acquisition of extended-spectrum β-lactamase resistance by S Typhimurium and blaCTX-M-27 genes in U.S. isolates of Salmonella have not previously been reported.
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Brouwer MSM, Tagg KA, Mevius DJ, Iredell JR, Bossers A, Smith HE, Partridge SR. IncI shufflons: Assembly issues in the next-generation sequencing era. Plasmid 2015; 80:111-7. [PMID: 25952328 DOI: 10.1016/j.plasmid.2015.04.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 04/15/2015] [Accepted: 04/20/2015] [Indexed: 11/18/2022]
Abstract
The shufflon is a site-specific recombination system first identified in the IncI1 plasmid R64. The R64 shufflon consists of four segments, separated by short repeats, which are rearranged and inverted by the recombinase protein Rci, generating diversity in the C-terminal end of the PilV protein. PilV is the tip adhesin of the thin pilus structure involved in bacterial conjugation and may play a role in determining recipient cell specificity during liquid mating. The variable arrangements of the shufflon region would be expected to make plasmid assembly difficult, particularly with short-read sequencing technology, but this is not usually mentioned in recent publications reporting IncI plasmid sequences. Here we discuss the issues we encountered with assembly of IncI1 sequence data obtained from the Roche-454 and Illumina platforms and make some suggestions for assembly of the shufflon region. Comparison of shufflon segments from a collection of IncI1 plasmids from The Netherlands and Australia, together with sequences available in GenBank, suggests that the number of shufflon segments present is conserved among plasmids grouped together by plasmid multi-locus sequencing typing but the different reported arrangements of shufflon segments may not be meaningful. This analysis also indicated that the sequences of the shufflon segments are highly conserved, with very few nucleotide changes.
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Affiliation(s)
- Michael S M Brouwer
- Central Veterinary Institute of Wageningen UR, PO Box 65, 8200 AB Lelystad, The Netherlands.
| | - Kaitlin A Tagg
- Centre for Infectious Diseases and Microbiology, Westmead Millennium Institute, The University of Sydney and Westmead Hospital, Westmead, NSW 2145, Australia
| | - Dik J Mevius
- Central Veterinary Institute of Wageningen UR, PO Box 65, 8200 AB Lelystad, The Netherlands
| | - Jonathan R Iredell
- Centre for Infectious Diseases and Microbiology, Westmead Millennium Institute, The University of Sydney and Westmead Hospital, Westmead, NSW 2145, Australia
| | - Alex Bossers
- Central Veterinary Institute of Wageningen UR, PO Box 65, 8200 AB Lelystad, The Netherlands
| | - Hilde E Smith
- Central Veterinary Institute of Wageningen UR, PO Box 65, 8200 AB Lelystad, The Netherlands
| | - Sally R Partridge
- Centre for Infectious Diseases and Microbiology, Westmead Millennium Institute, The University of Sydney and Westmead Hospital, Westmead, NSW 2145, Australia.
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Complete nucleotide sequence of a blaKPC-harboring IncI2 plasmid and its dissemination in New Jersey and New York hospitals. Antimicrob Agents Chemother 2013; 57:5019-25. [PMID: 23896467 DOI: 10.1128/aac.01397-13] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae strains have spread worldwide and become a significant public health threat. blaKPC, the plasmid-borne KPC gene, was frequently identified on numerous transferable plasmids in different incompatibility replicon groups. Here we report the complete nucleotide sequence of a novel blaKPC-3-harboring IncI2 plasmid, pBK15692, isolated from a multidrug-resistant K. pneumoniae ST258 strain isolated from a New Jersey hospital in 2005. pBK15692 is 78 kb in length and carries a backbone that is similar to those of other IncI2 plasmids (pR721, pChi7122-3, pHN1122-1, and pSH146-65), including the genes encoding type IV pili and shufflon regions. Comparative genomics analysis of IncI2 plasmids reveals that they possess a conserved plasmid backbone but are divergent with respect to the integration sites of resistance genes. In pBK15692, the blaKPC-3-harboring Tn4401 was inserted into a Tn1331 element and formed a nested transposon. A PCR scheme was designed to detect the prevalence of IncI2 and pBK15692-like plasmids from a collection of clinical strains from six New Jersey and New York hospitals isolated between 2007 and 2011. IncI2 plasmids were found in 46.2% isolates from 318 clinical K. pneumoniae strains. Notably, 59 pBK15692-like plasmids (23%) have been identified in 256 KPC-bearing K. pneumoniae strains, and all carried KPC-3 and belong to the epidemic ST258 clone. Our study revealed that the prevalence of IncI2 plasmids has been considerably underestimated. Further studies are needed to understand the distribution of this plasmid group in other health care regions and decipher the association between IncI2 plasmids and blaKPC-3-bearing ST258 strains.
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Van Houdt R, Leplae R, Lima-Mendez G, Mergeay M, Toussaint A. Towards a more accurate annotation of tyrosine-based site-specific recombinases in bacterial genomes. Mob DNA 2012; 3:6. [PMID: 22502997 PMCID: PMC3414803 DOI: 10.1186/1759-8753-3-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2011] [Accepted: 04/13/2012] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND Tyrosine-based site-specific recombinases (TBSSRs) are DNA breaking-rejoining enzymes. In bacterial genomes, they play a major role in the comings and goings of mobile genetic elements (MGEs), such as temperate phage genomes, integrated conjugative elements (ICEs) or integron cassettes. TBSSRs are also involved in the segregation of plasmids and chromosomes, the resolution of plasmid dimers and of co-integrates resulting from the replicative transposition of transposons. With the aim of improving the annotation of TBSSR genes in genomic sequences and databases, which so far is far from robust, we built a set of over 1,300 TBSSR protein sequences tagged with their genome of origin. We organized them in families to investigate: i) whether TBSSRs tend to be more conserved within than between classes of MGE types and ii) whether the (sub)families may help in understanding more about the function of TBSSRs associated in tandem or trios on plasmids and chromosomes. RESULTS A total of 67% of the TBSSRs in our set are MGE type specific. We define a new class of actinobacterial transposons, related to Tn554, containing one abnormally long TBSSR and one of typical size, and we further characterize numerous TBSSRs trios present in plasmids and chromosomes of α- and β-proteobacteria. CONCLUSIONS The simple in silico procedure described here, which uses a set of reference TBSSRs from defined MGE types, could contribute to greatly improve the annotation of tyrosine-based site-specific recombinases in plasmid, (pro)phage and other integrated MGE genomes. It also reveals TBSSRs families whose distribution among bacterial taxa suggests they mediate lateral gene transfer.
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Affiliation(s)
- Rob Van Houdt
- Unit of Microbiology (MIC), Belgian Nuclear Research Centre, SCK•CEN, Boeretang 200 Mol B-2400, Belgium
| | - Raphael Leplae
- Department of Informatics, Campus du Solbosch - CP197, 50 avenue F.D. Roosevelt, Bruxelles 1050, Belgium
| | - Gipsi Lima-Mendez
- Research Group of Bioinformatics and (Eco-)systems Biology, Department of Structural Biology, VIB, Pleinlaan 2, Brussels 1050, Belgium and Research Group of Bioinformatics and (Eco-)systems Biology, Microbiology Unit (MICR), Department of Applied Biological Sciences (DBIT), Vrije Universiteit Brussel, Pleinlaan 2, Brussels 1050, Belgium
| | - Max Mergeay
- Unit of Microbiology (MIC), Belgian Nuclear Research Centre, SCK•CEN, Boeretang 200 Mol B-2400, Belgium
| | - Ariane Toussaint
- Laboratoire Bioinformatique des Génomes et Réseaux (BiGRe), Université Libre de Bruxelles, Bvd du Triomphe, Bruxelles 1050, Belgium
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Johnson TJ, Shepard SM, Rivet B, Danzeisen JL, Carattoli A. Comparative genomics and phylogeny of the IncI1 plasmids: A common plasmid type among porcine enterotoxigenic Escherichia coli. Plasmid 2011; 66:144-51. [DOI: 10.1016/j.plasmid.2011.07.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 07/17/2011] [Accepted: 07/19/2011] [Indexed: 11/25/2022]
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de la Cruz F, Frost LS, Meyer RJ, Zechner EL. Conjugative DNA metabolism in Gram-negative bacteria. FEMS Microbiol Rev 2010; 34:18-40. [PMID: 19919603 DOI: 10.1111/j.1574-6976.2009.00195.x] [Citation(s) in RCA: 256] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Bacterial conjugation in Gram-negative bacteria is triggered by a signal that connects the relaxosome to the coupling protein (T4CP) and transferosome, a type IV secretion system. The relaxosome, a nucleoprotein complex formed at the origin of transfer (oriT), consists of a relaxase, directed to the nic site by auxiliary DNA-binding proteins. The nic site undergoes cleavage and religation during vegetative growth, but this is converted to a cleavage and unwinding reaction when a competent mating pair has formed. Here, we review the biochemistry of relaxosomes and ponder some of the remaining questions about the nature of the signal that begins the process.
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Garcillán-Barcia MP, Francia MV, de la Cruz F. The diversity of conjugative relaxases and its application in plasmid classification. FEMS Microbiol Rev 2009; 33:657-87. [PMID: 19396961 DOI: 10.1111/j.1574-6976.2009.00168.x] [Citation(s) in RCA: 375] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Bacterial conjugation is an efficient and sophisticated mechanism of DNA transfer among bacteria. While mobilizable plasmids only encode a minimal MOB machinery that allows them to be transported by other plasmids, conjugative plasmids encode a complete set of transfer genes (MOB1T4SS). The only essential ingredient of the MOB machinery is the relaxase, the protein that initiates and terminates conjugative DNA processing. In this review we compared the sequences and properties of the relaxase proteins contained in gene sequence databases. Proteins were arranged in families and phylogenetic trees constructed from the family alignments. This allowed the classification of conjugative transfer systems in six MOB families:MOB(F), MOB(H), MOB(Q), MOB(C), MOB(P) and MOB(V). The main characteristics of each family were reviewed. The phylogenetic relationships of the coupling proteins were also analysed and resulted in phylogenies congruent to those of the cognate relaxases. We propose that the sequences of plasmid relaxases can be used for plasmid classification. We hope our effort will provide researchers with a useful tool for further mining and analysing the plasmid universe both experimentally and in silico.
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Affiliation(s)
- María Pilar Garcillán-Barcia
- Departamento de Biología Molecular e Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-CSIC-IDICAN, Santander, Spain
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Abstract
Conservative site-specific recombination functions to create biological diversity in prokaryotes. Simple site-specific recombination systems consist of two recombination sites and a recombinase gene. The plasmid R64 shufflon contains seven recombination sites, which flank and separate four DNA segments. Site-specific recombinations mediated by the product of the rci gene between any two inverted recombination sites result in the inversion of four DNA segments independently or in groups. The shufflon functions as a biological switch to select one of seven C-terminal segments of the PilV proteins, which is a minor component of R64 thin pilus. The shufflon determines the recipient specificity in liquid matings of plasmid R64. Other multiple inversion systems as well as integrons, which are multiple insertion systems, are also described in this review.
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Affiliation(s)
- T Komano
- Department of Biology, Tokyo Metropolitan University, Japan.
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Komano T, Kim SR, Yoshida T. Mating variation by DNA inversions of shufflon in plasmid R64. ADVANCES IN BIOPHYSICS 1995; 31:181-93. [PMID: 7625273 DOI: 10.1016/0065-227x(95)99391-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Gene organization of the 54-kb transfer region of IncI1 plasmid R64 was deduced from the DNA sequence. Forty-eight ORFs were found in this region. A unique DNA rearrangement designated shufflon is located at the downstream region of an operon responsible for synthesis of thin pilus. The shufflon of R64 consists of four DNA segments, designated as A, B, C, and D, which are flanked and separated by seven 19-bp repeat sequences. Site-specific recombination mediated by the product of the rci gene between any two inverted repeats results in a complex DNA rearrangement. An analysis of open reading frames revealed that the shufflon is a biological switch to select one of seven C-terminal segments of the pilV genes. The products of pilV genes were shown to be components of thin pilus which was required for liquid mating. Seven R64 derivatives where the pilV genes were fixed in the seven C-terminal segments were constructed and their transfer frequencies in liquid mating were measured using various bacterial strains as recipients. Transfer frequencies of R64 in liquid mating strongly depended on the combination of C-terminal segments of the pilV genes in donor cells and bacterial strains of recipient cells, suggesting that the shufflon determines the recipient specificity in liquid mating of plasmid R64.
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Affiliation(s)
- T Komano
- Department of Biology, Tokyo Metropolitan University, Japan
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Abstract
The shufflon is a DNA region that undergoes complex rearrangement mediated by the product of a putative site-specific recombinase gene, rci. The DNA sequences of the shufflon region and the rci gene of IncI2 plasmid R721 were determined. The R721 shufflon consists of three invertible DNA segments that are homologous to the shufflon segments found in IncI1 plasmid R64. Structural analysis of open reading frames indicated that the R721 shufflon possibly functions as a biological switch for selecting one of the six pilV genes in which the N-terminal region is constant and the C-terminal region is variable. The R721 rci gene was shown to encode a basic protein of 374 amino acid residues.
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Affiliation(s)
- S R Kim
- Department of Biology, Tokyo Metropolitan University, Japan
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