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Santoro F, Fox V, Romeo A, Lazzeri E, Pozzi G, Iannelli F. Chromosomal integration of Tn5253 occurs downstream of a conserved 11-bp sequence of the rbgA gene in Streptococcus pneumoniae and in all the other known hosts of this integrative conjugative element (ICE). Mob DNA 2021; 12:25. [PMID: 34740368 PMCID: PMC8571831 DOI: 10.1186/s13100-021-00253-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 10/20/2021] [Indexed: 01/07/2023] Open
Abstract
Background Tn5253, a composite Integrative Conjugative Element (ICE) of Streptococcus pneumoniae carrying tet(M) and cat resistance determinants, was found to (i) integrate at specific 83-bp integration site (attB), (ii) produce circular forms joined by a 84-bp sequence (attTn), and (iii) restore the chromosomal integration site. The purpose of this study is to functionally characterize the attB in S. pneumoniae strains with different genetic backgrounds and in other bacterial species, and to investigate the presence of Tn5253 attB site into bacterial genomes. Results Analysis of representative Tn5253-carryng transconjugants obtained in S. pneumoniae strains with different genetic backgrounds and in other bacterial species, namely Streptococcus agalactiae, Streptococcus gordonii, Streptococcus pyogenes, and Enterococcus faecalis showed that: (i) Tn5253 integrates in rbgA of S. pneumoniae and in orthologous rbgA genes of other bacterial species, (ii) integration occurs always downstream of a 11-bp sequence conserved among streptococcal and enterococcal hosts, (iii) length of the attB site corresponds to length of the duplication after Tn5253 integration, (iv) attB duplication restores rbgA CDS, (v) Tn5253 produced circular forms containing the attTn site at a concentration ranging between 2.0 × 10−5 to 1.2 × 10−2 copies per chromosome depending on bacterial species and strain, (vi) reconstitution of attB sites occurred at 3.7 × 10−5 to 1.7 × 10−2 copies per chromosome. A database search of complete microbial genomes using Tn5253 attB as a probe showed that (i) thirteen attB variants were present in the 85 complete pneumococcal genomes, (ii) in 75 pneumococcal genomes (88.3 %), the attB site was 83 or 84 nucleotides in length, while in 10 (11.7 %) it was 41 nucleotides, (iii) in other 19 bacterial species attB was located in orthologous rbgA genes and its size ranged between 17 and 84 nucleotides, (iv) the 11-bp sequence, which correspond to the last 11 nucleotides of attB sites, is conserved among the different bacterial species and can be considered the core of the Tn5253 integration site. Conclusions A functional characterization of the Tn5253 attB integration site combined with genome analysis contributed to elucidating the potential of Tn5253 horizontal gene transfer among different bacterial species. Supplementary Information The online version contains supplementary material available at 10.1186/s13100-021-00253-z.
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Affiliation(s)
- Francesco Santoro
- Laboratory of Molecular Microbiology and Biotechnology (LAMMB), Department of Medical Biotechnologies, University of Siena, Siena, Italy
| | - Valeria Fox
- Laboratory of Molecular Microbiology and Biotechnology (LAMMB), Department of Medical Biotechnologies, University of Siena, Siena, Italy
| | - Alessandra Romeo
- Laboratory of Molecular Microbiology and Biotechnology (LAMMB), Department of Medical Biotechnologies, University of Siena, Siena, Italy
| | - Elisa Lazzeri
- Laboratory of Molecular Microbiology and Biotechnology (LAMMB), Department of Medical Biotechnologies, University of Siena, Siena, Italy
| | - Gianni Pozzi
- Laboratory of Molecular Microbiology and Biotechnology (LAMMB), Department of Medical Biotechnologies, University of Siena, Siena, Italy
| | - Francesco Iannelli
- Laboratory of Molecular Microbiology and Biotechnology (LAMMB), Department of Medical Biotechnologies, University of Siena, Siena, Italy.
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Santoro F, Romeo A, Pozzi G, Iannelli F. Excision and Circularization of Integrative Conjugative Element Tn 5253 of Streptococcus pneumoniae. Front Microbiol 2018; 9:1779. [PMID: 30108581 PMCID: PMC6079316 DOI: 10.3389/fmicb.2018.01779] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 07/16/2018] [Indexed: 11/13/2022] Open
Abstract
The integrative conjugative element (ICE) Tn5253 of Streptococcus pneumoniae, conferring resistance to tetracycline and chloramphenicol, was found integrated at a 83-bp specific target site (attB) located in the rbgA gene of the pneumococcal chromosome. PCR analysis of Tn5253-carrying strains showed evidence of precise excision of Tn5253 from the pneumococcal chromosome with production of (i) circular forms of the ICE in which the ends were joined by a 84-bp sequence (attTn), and (ii) reconstituted chromosomal attB. When integrated into the chromosome, Tn5253 was flanked by attL, identical to attB, and attR, identical to attTn. Circular forms of Tn5253 were present at a concentration of 3.8 × 10-4 copies per chromosome, whereas reconstituted attB sites were at 3.0 × 10-4 copies per chromosome. Deletion of int-xis of Tn5253 abolished production of circular forms (<7.1 × 10-6 copies per chromosome) and was associated to the lack of Tn5253 conjugal transfer suggesting, as expected, that Tn5253 circular form acts as a conjugation intermediate.
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Affiliation(s)
- Francesco Santoro
- Laboratory of Molecular Microbiology and Biotechnology, Department of Medical Biotechnologies, University of Siena, Siena, Italy
| | - Alessandra Romeo
- Laboratory of Molecular Microbiology and Biotechnology, Department of Medical Biotechnologies, University of Siena, Siena, Italy
| | - Gianni Pozzi
- Laboratory of Molecular Microbiology and Biotechnology, Department of Medical Biotechnologies, University of Siena, Siena, Italy
| | - Francesco Iannelli
- Laboratory of Molecular Microbiology and Biotechnology, Department of Medical Biotechnologies, University of Siena, Siena, Italy
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Polyvalent Proteins, a Pervasive Theme in the Intergenomic Biological Conflicts of Bacteriophages and Conjugative Elements. J Bacteriol 2017; 199:JB.00245-17. [PMID: 28559295 PMCID: PMC5512222 DOI: 10.1128/jb.00245-17] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 05/17/2017] [Indexed: 12/29/2022] Open
Abstract
Intense biological conflicts between prokaryotic genomes and their genomic parasites have resulted in an arms race in terms of the molecular “weaponry” deployed on both sides. Using a recursive computational approach, we uncovered a remarkable class of multidomain proteins with 2 to 15 domains in the same polypeptide deployed by viruses and plasmids in such conflicts. Domain architectures and genomic contexts indicate that they are part of a widespread conflict strategy involving proteins injected into the host cell along with parasite DNA during the earliest phase of infection. Their unique feature is the combination of domains with highly disparate biochemical activities in the same polypeptide; accordingly, we term them polyvalent proteins. Of the 131 domains in polyvalent proteins, a large fraction are enzymatic domains predicted to modify proteins, target nucleic acids, alter nucleotide signaling/metabolism, and attack peptidoglycan or cytoskeletal components. They further contain nucleic acid-binding domains, virion structural domains, and 40 novel uncharacterized domains. Analysis of their architectural network reveals both pervasive common themes and specialized strategies for conjugative elements and plasmids or (pro)phages. The themes include likely processing of multidomain polypeptides by zincin-like metallopeptidases and mechanisms to counter restriction or CRISPR/Cas systems and jump-start transcription or replication. DNA-binding domains acquired by eukaryotes from such systems have been reused in XPC/RAD4-dependent DNA repair and mitochondrial genome replication in kinetoplastids. Characterization of the novel domains discovered here, such as RNases and peptidases, are likely to aid in the development of new reagents and elucidation of the spread of antibiotic resistance. IMPORTANCE This is the first report of the widespread presence of large proteins, termed polyvalent proteins, predicted to be transmitted by genomic parasites such as conjugative elements, plasmids, and phages during the initial phase of infection along with their DNA. They are typified by the presence of multiple domains with disparate activities combined in the same protein. While some of these domains are predicted to assist the invasive element in replication, transcription, or protection of their DNA, several are likely to target various host defense systems or modify the host to favor the parasite's life cycle. Notably, DNA-binding domains from these systems have been transferred to eukaryotes, where they have been incorporated into DNA repair and mitochondrial genome replication systems.
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Wright LD, Grossman AD. Autonomous Replication of the Conjugative Transposon Tn916. J Bacteriol 2016; 198:3355-3366. [PMID: 27698087 PMCID: PMC5116939 DOI: 10.1128/jb.00639-16] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 09/29/2016] [Indexed: 01/14/2023] Open
Abstract
Integrative and conjugative elements (ICEs), also known as conjugative transposons, are self-transferable elements that are widely distributed among bacterial phyla and are important drivers of horizontal gene transfer. Many ICEs carry genes that confer antibiotic resistances to their host cells and are involved in the dissemination of these resistance genes. ICEs reside in host chromosomes but under certain conditions can excise to form a plasmid that is typically the substrate for transfer. A few ICEs are known to undergo autonomous replication following activation. However, it is not clear if autonomous replication is a general property of many ICEs. We found that Tn916, the first conjugative transposon identified, replicates autonomously via a rolling-circle mechanism. Replication of Tn916 was dependent on the relaxase encoded by orf20 of Tn916 The origin of transfer of Tn916, oriT(916), also functioned as an origin of replication. Using immunoprecipitation and mass spectrometry, we found that the relaxase (Orf20) and the two putative helicase processivity factors (Orf22 and Orf23) encoded by Tn916 likely interact in a complex and that the Tn916 relaxase contains a previously unidentified conserved helix-turn-helix domain in its N-terminal region that is required for relaxase function and replication. Lastly, we identified a functional single-strand origin of replication (sso) in Tn916 that we predict primes second-strand synthesis during rolling-circle replication. Together these results add to the emerging data that show that several ICEs replicate via a conserved, rolling-circle mechanism. IMPORTANCE Integrative and conjugative elements (ICEs) drive horizontal gene transfer and the spread of antibiotic resistances in bacteria. ICEs reside integrated in a host genome but can excise to create a plasmid that is the substrate for transfer to other cells. Here we show that Tn916, an ICE with broad host range, undergoes autonomous rolling-circle replication when in the plasmid form. We found that the origin of transfer functions as a double-stranded origin of replication and identified a single-stranded origin of replication. It was long thought that ICEs do not undergo autonomous replication. Our work adds to the evidence that ICEs replicate autonomously as part of their normal life cycle and indicates that diverse ICEs use the same replicative mechanism.
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Affiliation(s)
- Laurel D Wright
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Alan D Grossman
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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Molecular Epidemiology of Streptococcus pneumoniae Isolates from Children with Recurrent Upper Respiratory Tract Infections. PLoS One 2016; 11:e0158909. [PMID: 27415833 PMCID: PMC4945090 DOI: 10.1371/journal.pone.0158909] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 06/23/2016] [Indexed: 11/23/2022] Open
Abstract
A total of 125 isolates were recovered from adenoids and/or nasopharynx of 170 children aged 2 to 5 from south-east Poland; they had undergone adenoidectomy for recurrent and/or persistent symptoms of upper respiratory tract infections. Pneumococcal isolates were analyzed by phenotyping (serotyping and antimicrobial resistance tests) and genotyping together with the clonality of the pneumococcal isolates based on resistance determinants, transposon distribution and multilocus sequence typing (MLST). Serotypes 19F, 6B and 23F constituted 44.8% of the isolates. Among all of the strains, 44.8% showed decreased susceptibility to penicillin and resistance to co-trimoxazole (52.8%), tetracycline (38.4%), erythromycin (53.6%), clindamycin (52.8%) and chloramphenicol (27.2%) was observed. Tn6002 was found in 34.8% of erythromycin-resistant isolates while composite Tn2010—in 16.7% of erm(B)-carrying isolates that harboured also mef(E) gene. Tn3872-related elements were detected in 27.3% of erythromycin-resistant strains. In the majority of chloramphenicol-resistant catpC194-carrying isolates (79.4%), ICESp23FST81-family elements were detected. The genotyping showed that pneumococcal population was very heterogeneous; 82 sequence types (STs) were identified, and the most frequent contributed to not more than 8% of the isolates. Nearly 44% STs were novel, each of them was recovered only from one child. Four STs belonged to one of the 43 worldwide spread resistant pneumococcal clones currently accepted by Pneumococcal Molecular Epidemiology Network (PMEN), i.e. Spain 9V-3, Spain 23F-1, Norway NT-42 and Poland 6B-20, accounting for 12 (16.7%) of the 75 nonususceptible isolates, and five STs were single-locus variants of PMEN resistant clones (England 14–9, Spain 9V-3, Spain 23F-1, Greece 21–30, Denmark 14–32), accounting 9 (12%) of nonsusceptible isolates. A few MDR clones belonging to 6B and 19F serotypes found among preschool children emphasizes rather the role of clonal dissemination of local strains in the community than international clones spreading in the increase of resistance among pneumococcal strains.
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Resistance determinants and their association with different transposons in the antibiotic-resistant Streptococcus pneumoniae. BIOMED RESEARCH INTERNATIONAL 2015; 2015:836496. [PMID: 25883976 PMCID: PMC4391698 DOI: 10.1155/2015/836496] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 03/16/2015] [Accepted: 03/16/2015] [Indexed: 11/18/2022]
Abstract
Multiple resistance of Streptococcus pneumoniae is generally associated with their unique recombination-mediated genetic plasticity and possessing the mobile genetic elements. The aim of our study was to detect antibiotic resistance determinants and conjugative transposons in 138 antibiotic-resistant pneumococcal strains isolated from nasopharynx of healthy young children from Lublin, Poland. These strains resistant to tetracycline and/or to chloramphenicol/erythromycin/clindamycin were tested by PCR using the specific genes as markers. The presence of Tn916 family transposons, carrying tet(M) and int/xisTn916, was observed in all of the tested strains. Tn916 was detected in 16 strains resistant only to tetracycline. Tn6002 and Tn3872-related element were found among 99 erm(B)-carrying strains (83.8% and 3.0%, resp.). Eight strains harbouring mef(E) and erm(B) genes were detected, suggesting the presence of Tn2010 and Tn2017 transposons. Among 101 chloramphenicol-resistant strains, two variants of Tn5252-related transposon were distinguished depending on the presence of int/xis5252 genes specific for cat gene-containing Tn5252 (75.2% of strains) or int Sp23FST81 gene, specific for cat-containing ICESp23FST81 element (24.8% of strains). In 6 strains Tn916-like and Tn5252-like elements formed a Tn5253-like structure. Besides clonal dissemination of resistant strains of pneumococci in the population, horizontal transfer of conjugative transposons is an important factor of the high prevalence of antibiotic resistance.
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Chancey ST, Agrawal S, Schroeder MR, Farley MM, Tettelin H, Stephens DS. Composite mobile genetic elements disseminating macrolide resistance in Streptococcus pneumoniae. Front Microbiol 2015; 6:26. [PMID: 25709602 PMCID: PMC4321634 DOI: 10.3389/fmicb.2015.00026] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 01/08/2015] [Indexed: 01/17/2023] Open
Abstract
Macrolide resistance in Streptococcus pneumoniae emerged in the U.S. and globally during the early 1990's. The RNA methylase encoded by erm(B) and the macrolide efflux genes mef(E) and mel were identified as the resistance determining factors. These genes are disseminated in the pneumococcus on mobile, often chimeric elements consisting of multiple smaller elements. To better understand the variety of elements encoding macrolide resistance and how they have evolved in the pre- and post-conjugate vaccine eras, the genomes of 121 invasive and ten carriage isolates from Atlanta from 1994 to 2011 were analyzed for mobile elements involved in the dissemination of macrolide resistance. The isolates were selected to provide broad coverage of the genetic variability of antibiotic resistant pneumococci and included 100 invasive isolates resistant to macrolides. Tn916-like elements carrying mef(E) and mel on the Macrolide Genetic Assembly (Mega) and erm(B) on the erm(B) element and Tn917 were integrated into the pneumococcal chromosome backbone and into larger Tn5253-like composite elements. The results reported here include identification of novel insertion sites for Mega and characterization of the insertion sites of Tn916-like elements in the pneumococcal chromosome and in larger composite elements. The data indicate that integration of elements by conjugation was infrequent compared to recombination. Thus, it appears that conjugative mobile elements allow the pneumococcus to acquire DNA from distantly related bacteria, but once integrated into a pneumococcal genome, transformation and recombination is the primary mechanism for transmission of novel DNA throughout the pneumococcal population.
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Affiliation(s)
- Scott T Chancey
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine Atlanta, GA, USA ; Laboratories of Microbial Pathogenesis, Department of Veterans Affairs Medical Center Atlanta, GA, USA
| | - Sonia Agrawal
- Institute for Genome Sciences, University of Maryland School of Medicine Baltimore, MD, USA
| | - Max R Schroeder
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine Atlanta, GA, USA ; Laboratories of Microbial Pathogenesis, Department of Veterans Affairs Medical Center Atlanta, GA, USA
| | - Monica M Farley
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine Atlanta, GA, USA ; Laboratories of Microbial Pathogenesis, Department of Veterans Affairs Medical Center Atlanta, GA, USA
| | - Hervé Tettelin
- Institute for Genome Sciences, University of Maryland School of Medicine Baltimore, MD, USA ; Department of Microbiology and Immunology, University of Maryland School of Medicine Baltimore, MD, USA
| | - David S Stephens
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine Atlanta, GA, USA ; Laboratories of Microbial Pathogenesis, Department of Veterans Affairs Medical Center Atlanta, GA, USA
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Brown-Jaque M, Calero-Cáceres W, Muniesa M. Transfer of antibiotic-resistance genes via phage-related mobile elements. Plasmid 2015; 79:1-7. [PMID: 25597519 DOI: 10.1016/j.plasmid.2015.01.001] [Citation(s) in RCA: 144] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 01/12/2015] [Accepted: 01/13/2015] [Indexed: 11/29/2022]
Abstract
Antibiotic resistance is a major concern for society because it threatens the effective prevention of infectious diseases. While some bacterial strains display intrinsic resistance, others achieve antibiotic resistance by mutation, by the recombination of foreign DNA into the chromosome or by horizontal gene acquisition. In many cases, these three mechanisms operate together. Several mobile genetic elements (MGEs) have been reported to mobilize different types of resistance genes and despite sharing common features, they are often considered and studied separately. Bacteriophages and phage-related particles have recently been highlighted as MGEs that transfer antibiotic resistance. This review focuses on phages, phage-related elements and on composite MGEs (phages-MGEs) involved in antibiotic resistance mobility. We review common features of these elements, rather than differences, and provide a broad overview of the antibiotic resistance transfer mechanisms observed in nature, which is a necessary first step to controlling them.
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Affiliation(s)
- Maryury Brown-Jaque
- Department of Microbiology, Faculty of Biology, University of Barcelona, Barcelona, Spain
| | - William Calero-Cáceres
- Department of Microbiology, Faculty of Biology, University of Barcelona, Barcelona, Spain
| | - Maite Muniesa
- Department of Microbiology, Faculty of Biology, University of Barcelona, Barcelona, Spain.
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Mingoia M, Morici E, Brenciani A, Giovanetti E, Varaldo PE. Genetic basis of the association of resistance genes mef(I) (macrolides) and catQ (chloramphenicol) in streptococci. Front Microbiol 2015; 5:747. [PMID: 25610433 PMCID: PMC4285128 DOI: 10.3389/fmicb.2014.00747] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 12/09/2014] [Indexed: 12/26/2022] Open
Abstract
In streptococci mef(I) and catQ, two relatively uncommon macrolide and chloramphenicol resistance genes, respectively, are typically linked in a genetic module designated IQ module. Though variable, the module consistently encompasses, and is sometimes reduced to, a conserved ∼5.8-kb mef(I)-catQ fragment. The prototype IQ module was described in Streptococcus pneumoniae. IQ-like modules have subsequently been detected in Streptococcus pyogenes and in different species of viridans group streptococci, where mef(E) may be found instead of mef(I). Three genetic elements, one carrying the prototype IQ module from S. pneumoniae and two carrying different, defective IQ modules from S. pyogenes, have recently been characterized. All are integrative and conjugative elements (ICEs) belonging to the Tn5253 family, and have been designated ICESpn529IQ, ICESpy029IQ and ICESpy005IQ, respectively. ICESpy029IQ and ICESpy005IQ were the first Tn5253 family ICEs to be described in S. pyogenes. A wealth of new information has been obtained by comparing their genetic organization, chromosomal integration, and transferability. The origin of the IQ module is unknown. The mechanism by which it spreads in streptococci is discussed.
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Affiliation(s)
- Marina Mingoia
- Unit of Microbiology, Department of Biomedical Sciences and Public Health, School of Medicine, Polytechnic University of Marche Ancona, Italy
| | - Eleonora Morici
- Unit of Microbiology, Department of Biomedical Sciences and Public Health, School of Medicine, Polytechnic University of Marche Ancona, Italy
| | - Andrea Brenciani
- Unit of Microbiology, Department of Biomedical Sciences and Public Health, School of Medicine, Polytechnic University of Marche Ancona, Italy
| | - Eleonora Giovanetti
- Unit of Microbiology, Department of Life and Environmental Sciences, Polytechnic University of Marche Ancona, Italy
| | - Pietro E Varaldo
- Unit of Microbiology, Department of Biomedical Sciences and Public Health, School of Medicine, Polytechnic University of Marche Ancona, Italy
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Andam CP, Hanage WP. Mechanisms of genome evolution of Streptococcus. INFECTION GENETICS AND EVOLUTION 2014; 33:334-42. [PMID: 25461843 DOI: 10.1016/j.meegid.2014.11.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 11/05/2014] [Accepted: 11/07/2014] [Indexed: 10/24/2022]
Abstract
The genus Streptococcus contains 104 recognized species, many of which are associated with human or animal hosts. A globally prevalent human pathogen in this group is Streptococcus pneumoniae (the pneumococcus). While being a common resident of the upper respiratory tract, it is also a major cause of otitis media, pneumonia, bacteremia and meningitis, accounting for a high burden of morbidity and mortality worldwide. Recent findings demonstrate the importance of recombination and selection in driving the population dynamics and evolution of different pneumococcal lineages, allowing them to successfully evade the impacts of selective pressures such as vaccination and antibiotic treatment. We highlight the ability of pneumococci to respond to these pressures through processes including serotype replacement, capsular switching and horizontal gene transfer (HGT) of antibiotic resistance genes. The challenge in controlling this pathogen also lies in the exceptional genetic and phenotypic variation among different pneumococcal lineages, particularly in terms of their pathogenicity and resistance to current therapeutic strategies. The widespread use of pneumococcal conjugate vaccines, which target only a small subset of the more than 90 pneumococcal serotypes, provides us with a unique opportunity to elucidate how the processes of selection and recombination interact to generate a remarkable level of plasticity and heterogeneity in the pneumococcal genome. These processes also play an important role in the emergence and spread of multi-resistant strains, which continues to pose a challenge in disease control and/or eradication. The application of population of genomic approaches at different spatial and temporal scales will help improve strategies to control this global pathogen, and potentially other pathogenic streptococci.
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Affiliation(s)
- Cheryl P Andam
- Department of Epidemiology, Harvard School of Public Health, Boston, MA 02115, USA
| | - William P Hanage
- Department of Epidemiology, Harvard School of Public Health, Boston, MA 02115, USA.
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Santoro F, Vianna ME, Roberts AP. Variation on a theme; an overview of the Tn916/Tn1545 family of mobile genetic elements in the oral and nasopharyngeal streptococci. Front Microbiol 2014; 5:535. [PMID: 25368607 PMCID: PMC4202715 DOI: 10.3389/fmicb.2014.00535] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 09/25/2014] [Indexed: 11/17/2022] Open
Abstract
The oral and nasopharyngeal streptococci are a major part of the normal microbiota in humans. Most human associated streptococci are considered commensals, however, a small number of them are pathogenic, causing a wide range of diseases including oral infections such as dental caries and periodontitis and diseases at other body sites including sinusitis and endocarditis, and in the case of Streptococcus pneumoniae, meningitis. Both phenotypic and sequence based studies have shown that the human associated streptococci from the mouth and nasopharynx harbor a large number of antibiotic resistance genes and these are often located on mobile genetic elements (MGEs) known as conjugative transposons or integrative and conjugative elements of the Tn916/Tn1545 family. These MGEs are responsible for the spread of the resistance genes between streptococci and also between streptococci and other bacteria. In this review we describe the resistances conferred by, and the genetic variations between the many different Tn916-like elements found in recent studies of oral and nasopharyngeal streptococci and show that Tn916-like elements are important mediators of antibiotic resistance genes within this genus. We will also discuss the role of the oral environment and how this is conducive to the transfer of these elements and discuss the contribution of both transformation and conjugation on the transfer and evolution of these elements in different streptococci.
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Affiliation(s)
- Francesco Santoro
- Laboratory of Molecular Microbiology and Biotechnology, Department of Medical Biotechnologies, University of SienaSiena, Italy
| | - Morgana E. Vianna
- Unit of Endodontology, UCL Eastman Dental Institute, University College LondonLondon, UK
| | - Adam P. Roberts
- Department of Microbial Diseases, UCL Eastman Dental Institute, University College LondonLondon, UK
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Tn5253 family integrative and conjugative elements carrying mef(I) and catQ determinants in Streptococcus pneumoniae and Streptococcus pyogenes. Antimicrob Agents Chemother 2014; 58:5886-93. [PMID: 25070090 DOI: 10.1128/aac.03638-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The linkage between the macrolide efflux gene mef(I) and the chloramphenicol inactivation gene catQ was first described in Streptococcus pneumoniae (strain Spn529), where the two genes are located in a module designated IQ element. Subsequently, two different defective IQ elements were detected in Streptococcus pyogenes (strains Spy029 and Spy005). The genetic elements carrying the three IQ elements were characterized, and all were found to be Tn5253 family integrative and conjugative elements (ICEs). The ICE from S. pneumoniae (ICESpn529IQ) was sequenced, whereas the ICEs from S. pyogenes (ICESpy029IQ and ICESpy005IQ, the first Tn5253-like ICEs reported in this species) were characterized by PCR mapping, partial sequencing, and restriction analysis. ICESpn529IQ and ICESpy029IQ were found to share the intSp 23FST81 integrase gene and an identical Tn916 fragment, whereas ICESpy005IQ has int5252 and lacks Tn916. All three ICEs were found to lack the linearized pC194 plasmid that is usually associated with Tn5253-like ICEs, and all displayed a single copy of a toxin-antitoxin operon that is typically contained in the direct repeats flanking the excisable pC194 region when this region is present. Two different insertion sites of the IQ elements were detected, one in ICESpn529IQ and ICESpy029IQ, and another in ICESpy005IQ. The chromosomal integration of the three ICEs was site specific, depending on the integrase (intSp 23FST81 or int5252). Only ICESpy005IQ was excised in circular form and transferred by conjugation. By transformation, mef(I) and catQ were cotransferred at a high frequency from S. pyogenes Spy005 and at very low frequencies from S. pneumoniae Spn529 and S. pyogenes Spy029.
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Donkor ES, Badoe EV. Insights into Pneumococcal Pathogenesis and Antibiotic Resistance. ACTA ACUST UNITED AC 2014. [DOI: 10.4236/aim.2014.410069] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Wyres KL, van Tonder A, Lambertsen LM, Hakenbeck R, Parkhill J, Bentley SD, Brueggemann AB. Evidence of antimicrobial resistance-conferring genetic elements among pneumococci isolated prior to 1974. BMC Genomics 2013; 14:500. [PMID: 23879707 PMCID: PMC3726389 DOI: 10.1186/1471-2164-14-500] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 07/23/2013] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Antimicrobial resistance among pneumococci has greatly increased over the past two to three decades. Resistance to tetracycline (tet(M)), chloramphenicol (cat) and macrolides (erm(B) and/or mef(A/E)) is generally conferred by acquisition of specific genes that are associated with mobile genetic elements, including those of the Tn916 and Tn5252 families. The first tetracycline-, chloramphenicol- and macrolide-resistant pneumococci were detected between 1962 and 1970; however, until now the oldest pneumococcus shown to harbour Tn916 and/or Tn5252 was isolated in 1974. In this study the genomes of 38 pneumococci isolated prior to 1974 were probed for the presence of tet(M), cat, erm(B), mef(A/E) and int (integrase) to indicate the presence of Tn916/Tn5252-like elements. RESULTS Two Tn916-like, tet(M)-containing, elements were identified among pneumococci dated 1967 and 1968. The former element was highly similar to that of the PMEN1 multidrug-resistant, globally-distributed pneumococcal reference strain, which was isolated in 1984. The latter element was associated with a streptococcal phage. A third, novel genetic element, designated ICESpPN1, was identified in the genome of an isolate dated 1972. ICESpPN1 contained a region of similarity to Tn5252, a region of similarity to a pneumococcal pathogenicity island and novel lantibiotic synthesis/export-associated genes. CONCLUSIONS These data confirm the existence of pneumococcal Tn916 elements in the first decade within which pneumococcal tetracycline resistance was described. Furthermore, the discovery of ICESpPN1 demonstrates the dynamic variability of pneumococcal genetic elements and is contrasted with the evidence for Tn916 stability.
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Affiliation(s)
- Kelly L Wyres
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, United Kingdom
| | - Andries van Tonder
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, United Kingdom
| | - Lotte M Lambertsen
- Department of Microbiology Surveillance and Research, Statens Serum Institut, 5 Artillerivej, Copenhagen 2300, Denmark
| | - Regine Hakenbeck
- Department of Microbiology, University Kaiserslautern, Kaiserslautern, Germany
| | - Julian Parkhill
- Pathogen Genomics Team, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, United Kingdom
| | - Stephen D Bentley
- Pathogen Genomics Team, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, United Kingdom
| | - Angela B Brueggemann
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, United Kingdom
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15
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Bhatty M, Laverde Gomez JA, Christie PJ. The expanding bacterial type IV secretion lexicon. Res Microbiol 2013; 164:620-39. [PMID: 23542405 DOI: 10.1016/j.resmic.2013.03.012] [Citation(s) in RCA: 121] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 12/01/2012] [Accepted: 02/05/2013] [Indexed: 02/06/2023]
Abstract
The bacterial type IV secretion systems (T4SSs) comprise a biologically diverse group of translocation systems functioning to deliver DNA or protein substrates from donor to target cells generally by a mechanism dependent on establishment of direct cell-to-cell contact. Members of one T4SS subfamily, the conjugation systems, mediate the widespread and rapid dissemination of antibiotic resistance and virulence traits among bacterial pathogens. Members of a second subfamily, the effector translocators, are used by often medically-important pathogens to deliver effector proteins to eukaryotic target cells during the course of infection. Here we summarize our current understanding of the structural and functional diversity of T4SSs and of the evolutionary processes shaping this diversity. We compare mechanistic and architectural features of T4SSs from Gram-negative and -positive species. Finally, we introduce the concept of the 'minimized' T4SSs; these are systems composed of a conserved set of 5-6 subunits that are distributed among many Gram-positive and some Gram-negative species.
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Affiliation(s)
- Minny Bhatty
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, 6431 Fannin, Houston, TX 77030, USA
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16
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Genetic diversity of Tn916-related transposons among drug-resistant Streptococcus pneumoniae isolates colonizing healthy children in Venezuela. Antimicrob Agents Chemother 2011; 55:4930-2. [PMID: 21788464 DOI: 10.1128/aac.00242-11] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Among a collection of 48 multidrug-resistant pneumococcal strains colonizing healthy children in a small municipality of Mérida, Venezuela, we identified sequence types (STs) related to a variety of internationally spreading drug-resistant clones, as well as ST135, thus far isolated only in Europe. The clones invariably harbored one or more of the Tn916-related transposons Tn3872, Tn5253, Tn6002, Tn2009, and Tn2010. Finally, our data suggest both structural rearrangements in certain transposons and occurrence of novel transposable elements.
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17
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Roberts AP, Mullany P. Tn916-like genetic elements: a diverse group of modular mobile elements conferring antibiotic resistance. FEMS Microbiol Rev 2011; 35:856-71. [PMID: 21658082 DOI: 10.1111/j.1574-6976.2011.00283.x] [Citation(s) in RCA: 157] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Antibiotic-resistant Gram-positive bacteria are responsible for morbidity and mortality in healthcare environments. Enterococcus faecium, Enterococcus faecalis, Staphylococcus aureus and Streptococcus pneumoniae can all exhibit clinically relevant multidrug resistance phenotypes due to acquired resistance genes on mobile genetic elements. It is possible that clinically relevant multidrug-resistant Clostridium difficile strains will appear in the future, as the organism is adept at acquiring mobile genetic elements (plasmids and transposons). Conjugative transposons of the Tn916/Tn1545 family, which carry major antibiotic resistance determinants, are transmissible between these different bacteria by a conjugative mechanism during which the elements are excised by a staggered cut from donor cells, converted to a circular form, transferred by cell-cell contact and inserted into recipient cells by a site-specific recombinase. The ability of these conjugative transposons to acquire additional, clinically relevant antibiotic resistance genes importantly contributes to the emergence of multidrug resistance.
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Affiliation(s)
- Adam P Roberts
- Department of Microbial Diseases, UCL Eastman Dental Institute, University College London, London, UK
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18
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Harvey RM, Stroeher UH, Ogunniyi AD, Smith-Vaughan HC, Leach AJ, Paton JC. A variable region within the genome of Streptococcus pneumoniae contributes to strain-strain variation in virulence. PLoS One 2011; 6:e19650. [PMID: 21573186 PMCID: PMC3088708 DOI: 10.1371/journal.pone.0019650] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 04/08/2011] [Indexed: 01/12/2023] Open
Abstract
The bacterial factors responsible for the variation in invasive potential between different clones and serotypes of Streptococcus pneumoniae are largely unknown. Therefore, the isolation of rare serotype 1 carriage strains in Indigenous Australian communities provided a unique opportunity to compare the genomes of non-invasive and invasive isolates of the same serotype in order to identify such factors. The human virulence status of non-invasive, intermediately virulent and highly virulent serotype 1 isolates was reflected in mice and showed that whilst both human non-invasive and highly virulent isolates were able to colonize the murine nasopharynx equally, only the human highly virulent isolates were able to invade and survive in the murine lungs and blood. Genomic sequencing comparisons between these isolates identified 8 regions >1 kb in size that were specific to only the highly virulent isolates, and included a version of the pneumococcal pathogenicity island 1 variable region (PPI-1v), phage-associated adherence factors, transporters and metabolic enzymes. In particular, a phage-associated endolysin, a putative iron/lead permease and an operon within PPI-1v exhibited niche-specific changes in expression that suggest important roles for these genes in the lungs and blood. Moreover, in vivo competition between pneumococci carrying PPI-1v derivatives representing the two identified versions of the region showed that the version of PPI-1v in the highly virulent isolates was more competitive than the version from the less virulent isolates in the nasopharyngeal tissue, blood and lungs. This study is the first to perform genomic comparisons between serotype 1 isolates with distinct virulence profiles that correlate between mice and humans, and has highlighted the important role that hypervariable genomic loci, such as PPI-1v, play in pneumococcal disease. The findings of this study have important implications for understanding the processes that drive progression from colonization to invasive disease and will help direct the development of novel therapeutic strategies.
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Affiliation(s)
- Richard M. Harvey
- Research Centre for Infectious Diseases, School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia, Australia
| | - Uwe H. Stroeher
- Research Centre for Infectious Diseases, School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia, Australia
| | - Abiodun D. Ogunniyi
- Research Centre for Infectious Diseases, School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia, Australia
| | - Heidi C. Smith-Vaughan
- Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia
| | - Amanda J. Leach
- Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia
| | - James C. Paton
- Research Centre for Infectious Diseases, School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia, Australia
- * E-mail:
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19
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Heterogeneity of Tn5253-like composite elements in clinical Streptococcus pneumoniae isolates. Antimicrob Agents Chemother 2011; 55:1453-9. [PMID: 21263055 DOI: 10.1128/aac.01087-10] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Several drug resistances in Streptococcus pneumoniae are associated with mobile genetic elements, which are loosely subdivided into a group of smaller (18- to 27-kb) and a group of larger (>50-kb) elements. While the elements of the former group, which typically carry the tetracycline resistance determinant tet(M) and whose prototype is Tn916 (18 kb), have been studied extensively, the larger elements, whose prototype is Tn5253 (∼65.5 kb), are not as well explored. Tn5253 is a composite structure consisting of two independent conjugative transposons, Tn5251 (which is virtually identical to Tn916) and Tn5252 (∼47.5 kb), with the former inserted into the latter. Tn5252, which so far has only partially been sequenced, carries an integrase gene, driving its site-specific insertion into the host cell genome, and the chloramphenicol resistance cat(pC194) determinant. This study investigated 20 clinical isolates of S. pneumoniae, which were selected on the basis of cat(pC194)-mediated chloramphenicol resistance. All 20 isolates harbored a Tn5253-like element. The composite elements (some of which have been completely sequenced) demonstrated considerable heterogeneity that stemmed from a dual variability: in the Tn5252-like element, due primarily to differences in the integrase gene but also to differences in cargo genes and in the overall genetic organization, and in the Tn916-like element, with the possible involvement, besides Tn916, of a number of Tn916 family pneumococcal elements carrying different erythromycin resistance genes. In mating experiments, only one composite element, containing a less typical Tn916 family element, appeared to be nonmobile. Being part of a Tn5253-like composite element may confer on some Tn916-like transposons, which are apparently nontransferable as independent genetic elements, the ability to be mobilized.
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20
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Sadowy E, Matynia B, Hryniewicz W. Population structure, virulence factors and resistance determinants of invasive, non-invasive and colonizing Streptococcus agalactiae in Poland. J Antimicrob Chemother 2010; 65:1907-14. [PMID: 20584746 DOI: 10.1093/jac/dkq230] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
OBJECTIVES To analyse Streptococcus agalactiae (group B Streptococcus; GBS) isolates collected in Poland from various human infections and carriage in respect of their clonality, distribution of virulence factors and antimicrobial resistance determinants, including the detection of transposons involved in the dissemination of antimicrobial resistance. METHODS One hundred and fourteen GBS isolates were analysed by multilocus sequence typing (MLST), serotyping and detection of alp genes of the alpha-like-protein (Alp) family. Determinants of resistance to macrolides and tetracycline, and associated transposons, were detected by PCR and analysed by sequencing. RESULTS GBS isolates represented 30 different sequence types (STs), grouped in four clonal complexes (CCs), and belonged to seven serotypes. Serotype III was predominant (36.0%), followed by Ia, V, Ib, II, IV and VI. The most common alp genes were rib (26.3%) and alp1/alp5 (23.7%). The bac gene encoding the beta-compound of the surface C-protein was present in 17.5% of isolates. Erythromycin resistance (18.4% of isolates) was found in all CCs, but was associated with serotype V and ST1. The most prevalent determinant of resistance was erm(B), usually located on the Tn3872-like transposon. Several changes were observed in the regulatory region of erm(B), some of them resulting in elevated ketolide MICs. Resistance to tetracycline was ubiquitous (91.2%) and its most common determinant was tet(M), occurring in several variants that were typically carried on Tn916-family transposons. CONCLUSIONS Analysis of bacterial serotypes, alp genes and antimicrobial resistance determinants in the background of MLST-based population structure strengthened evidence of the importance of horizontal gene transfer in GBS evolution.
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Affiliation(s)
- Ewa Sadowy
- National Medicines Institute, ul Chełmska 30/34, 00-725 Warsaw, Poland.
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21
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Santoro F, Oggioni MR, Pozzi G, Iannelli F. Nucleotide sequence and functional analysis of the tet (M)-carrying conjugative transposon Tn5251 of Streptococcus pneumoniae. FEMS Microbiol Lett 2010; 308:150-8. [PMID: 20487027 DOI: 10.1111/j.1574-6968.2010.02002.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The Tn916-like genetic element Tn5251 is part of the composite conjugative transposon (CTn) Tn5253 of Streptococcus pneumoniae, a 64.5-kb chromosomal element originally called Omega(cat-tet) BM6001. DNA sequence analysis showed that Tn5251 is 18 033-bp long and contains 22 ORFs, 20 of which have the same direction of transcription. Annotation was possible for 11 out of 22 ORFs, including the tet(M) tetracycline resistance gene and int and xis involved in the integration/excision process. Autonomous copies of Tn5251 were generated during matings of Tn5253-containing donors with S. pneumoniae and Enterococcus faecalis. Tn5251 was shown to integrate at different sites in the bacterial chromosome. It behaves as a fully functional CTn capable of independent conjugal transfer to a variety of bacterial species including S. pneumoniae, Streptococcus gordonii, Streptococcus pyogenes, Streptococcus agalactiae, E. faecalis and Bacillus subtilis. The excision of Tn5251 produces a circular intermediate and a deletion in Tn5253 at a level of 1.2 copies per 10(5) chromosomes.
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Affiliation(s)
- Francesco Santoro
- Laboratory of Molecular Microbiology and Biotechnology (LAMMB), Department of Molecular Biology, University of Siena, Siena, Italy
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