Diversity of putative Tn5253-like elements in Streptococcus pneumoniae

Henderson-Begg, Stephanie; Roberts, Adam P.; Hall, Lucinda M. C.

doi:10.1016/j.ijantimicag.2008.10.002

Cited by 23 publications

(25 citation statements)

References 16 publications

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“…The only correlation between typing data and particular composite elements was the fact that four of the five isolates harboring Tn6058 belonged to serotype 3 and PFGE type A. Such heterogeneity confirms and affords further insights into the diversity of putative Tn5253-like pneumococcal elements, which has recently been reported by Henderson-Begg et al (14) on the basis of combined analysis of selected genes and antibiogram data. Remarkably, that study also underscored that these composite elements appear to be prevalent among internationally recognized pandemic clones of S. pneumoniae.…”

Section: Vol 55 2011 Heterogeneity Of Tn5253-like Elements In S Pnsupporting

confidence: 79%

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Heterogeneity of Tn 5253 -Like Composite Elements in Clinical Streptococcus pneumoniae Isolates

Mingoia¹,

Tili²,

Manso³

et al. 2011

Antimicrob Agents Chemother

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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 (ϳ65.5 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 (ϳ47.5 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.A unique recombination-mediated genetic plasticity is a distinctive feature of Streptococcus pneumoniae (3) and a key to its success as a pathogen. In this context, a cause for serious concern is the emergence and increasing spread of multidrugresistant clinical pneumococci (28), where multiple resistance is generally associated with mobile genetic elements. Although the nomenclature for such elements is evolving, they are often referred to as transposons or as integrative and conjugative elements (ICEs) (21, 33). Pneumococcal mobile elements (which are also found in other streptococci and Gram-positive cocci) can be loosely subdivided into two major groups of smaller (18-to 27-kb) and larger (Ͼ50-kb) elements (2, 23).The smaller genetic elements form the widespread Tn916 family, so called from the prototype, Tn916, an 18-kb transposon originally detected in Enterococcus faecalis when it was still regarded as a Streptococcus species (12). Tn916 family elements typically contain integrase (int 916 ) and excisionase (xis 916 ) genes and carry the tetracycline (TET) resistance determinant tet(M). These elements have been widely investigated, leading to the discovery of a variety of Tn916 ...

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Section: Vol 55 2011 Heterogeneity Of Tn5253-like Elements In S Pnsupporting

confidence: 79%

“…Recently, variability of some genes of the Tn5252 LT region in clinical isolates of pneumococci has been reported (14). Moreover, analysis of the complete chromosome sequences of multiresistant S. pneumoniae isolates has disclosed new larger genetic elements, such as ICESp23FST81 (ϳ81 kb; accession no.…”

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confidence: 99%

Heterogeneity of Tn 5253 -Like Composite Elements in Clinical Streptococcus pneumoniae Isolates

Mingoia¹,

Tili²,

Manso³

et al. 2011

Antimicrob Agents Chemother

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“…The XRE-like helix-turn-helix domain is conserved in many homologues of the orf20-encoded relaxase (see Materials and Methods), including the relaxases of Tn916-related elements present in multidrug-resistant C. difficile strain 630 (CTn7) and in pathogenic strains of S. pneumoniae (Tn5253), and in relaxases present in putative mobile elements from several Gram-positive species (6,26,68) (Fig. 4).…”

Section: Rationalementioning

confidence: 99%

Autonomous Replication of the Conjugative Transposon Tn916

2016

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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. Integrative and conjugative elements (ICEs), also called conjugative transposons, are mobile genetic elements that encode proteins that mediate transfer of the element from the host cell (donor) to a recipient by conjugation. ICEs often contain additional (cargo) genes that can provide a selective advantage to the host cells (reviewed in references 1 and 2). Most ICEs have been identified based on their cargo genes and the phenotypes conferred. For example, many ICEs carry genes encoding antibiotic resistances. The horizontal dissemination of ICEs and their associated cargo genes is a major driver of bacterial genome plasticity and evolution and the s...

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“…In recent years, considerable progress has been made in the understanding of those large genetic elements, a distinct family of ICEs, whose prototype is Tn5253, a conjugative composite structure resulting from the insertion of Tn5251 (virtually identical to Tn916) into Tn5252 (10). The complete sequence of Tn5253 has become available and has lately been analyzed (11), and several studies have recently stressed the heterogeneity of Tn5253-like composite elements and their integrase genes (int 5252 or int Sp23FST81 ) (12)(13)(14)(15)(16)(17).…”

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Tn 5253 Family Integrative and Conjugative Elements Carrying mef (I) and catQ Determinants in Streptococcus pneumoniae and Streptococcus pyogenes

Mingoia

Morici

Morroni

et al. 2014

Antimicrob Agents Chemother

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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 int Sp23FST81 integrase gene and an identical Tn916 fragment, whereas ICESpy005IQ has int 5252 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 (int Sp23FST81 or int 5252 ). 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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Diversity of putative Tn5253-like elements in Streptococcus pneumoniae

Cited by 23 publications

References 16 publications

Heterogeneity of Tn 5253 -Like Composite Elements in Clinical Streptococcus pneumoniae Isolates

Heterogeneity of Tn 5253 -Like Composite Elements in Clinical Streptococcus pneumoniae Isolates

Autonomous Replication of the Conjugative Transposon Tn916

Tn 5253 Family Integrative and Conjugative Elements Carrying mef (I) and catQ Determinants in Streptococcus pneumoniae and Streptococcus pyogenes

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