Key components of the eight classes of type IV secretion systems involved in bacterial conjugation or protein secretion

Guglielmini, Julien; Néron, Bertrand; Abby, Sophie S.; Garcillán-Barcia, M. Pilar; Cruz, Fernando de la; Rocha, Eduardo P. C.

doi:10.1093/nar/gku194

Cited by 191 publications

(224 citation statements)

References 91 publications

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“…We scanned genomes for genes encoding components of the conjugation machinery: Relaxases, coupling proteins, and type 4 secretion systems (T4SS) (Guglielmini et al 2014). We identified 23 putative conjugation systems in the genus, of which 11 were classified as MPF F (family of the F plasmid), 4 MPF I (family of the R64 plasmid), and 8 MPF T (family of the Ti plasmid).…”

Section: Resultsmentioning

confidence: 99%

The Genomic Diversification of the Whole Acinetobacter Genus: Origins, Mechanisms, and Consequences

Touchon

Cury

Yoon

et al. 2014

Genome Biology and Evolution

238

226

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Bacterial genomics has greatly expanded our understanding of microdiversification patterns within a species, but analyses at higher taxonomical levels are necessary to understand and predict the independent rise of pathogens in a genus. We have sampled, sequenced, and assessed the diversity of genomes of validly named and tentative species of the Acinetobacter genus, a clade including major nosocomial pathogens and biotechnologically important species. We inferred a robust global phylogeny and delimited several new putative species. The genus is very ancient and extremely diverse: Genomes of highly divergent species share more orthologs than certain strains within a species. We systematically characterized elements and mechanisms driving genome diversification, such as conjugative elements, insertion sequences, and natural transformation. We found many error-prone polymerases that may play a role in resistance to toxins, antibiotics, and in the generation of genetic variation. Surprisingly, temperate phages, poorly studied in Acinetobacter, were found to account for a significant fraction of most genomes. Accordingly, many genomes encode clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems with some of the largest CRISPR-arrays found so far in bacteria. Integrons are strongly overrepresented in Acinetobacter baumannii, which correlates with its frequent resistance to antibiotics. Our data suggest that A. baumannii arose from an ancient population bottleneck followed by population expansion under strong purifying selection. The outstanding diversification of the species occurred largely by horizontal transfer, including some allelic recombination, at specific hotspots preferentially located close to the replication terminus. Our work sets a quantitative basis to understand the diversification of Acinetobacter into emerging resistant and versatile pathogens.

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Section: Resultsmentioning

confidence: 99%

The Genomic Diversification of the Whole Acinetobacter Genus: Origins, Mechanisms, and Consequences

Touchon

Cury

Yoon

et al. 2014

Genome Biology and Evolution

238

226

View full text Add to dashboard Cite

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“…Determination of the functional role and protein-protein interactions of several Tcp proteins has resulted in the development of a model of the C. perfringens transfer apparatus (20). A recent classification of T4SSs involved in conjugation identified the conjugation region from pCW3 as belonging to the MPF FA class that includes Tn916 and other integrative and conjugative elements from the Firmicutes and Actinobacteria (46). Several specific protein profiles were identified in this family, including the unique TcpE protein family, which lacked homologs to components from other conjugation T4SS classes.…”

Section: Discussionmentioning

confidence: 99%

Two Novel Membrane Proteins, TcpD and TcpE, Are Essential for Conjugative Transfer of pCW3 in Clostridium perfringens

et al. 2015

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The anaerobic pathogen Clostridium perfringens encodes either toxin genes or antibiotic resistance determinants on a unique family of conjugative plasmids that have a novel conjugation region, the tcp locus. Studies of the paradigm conjugative plasmid from C. perfringens, the 47-kb tetracycline resistance plasmid pCW3, have identified several tcp-encoded proteins that are involved in conjugative transfer and form part of the transfer apparatus. In this study, the role of the conserved hypothetical proteins TcpD, TcpE, and TcpJ was examined. Mutation and complementation analyses showed that TcpD and TcpE were essential for the conjugative transfer of pCW3, whereas TcpJ was not required. To analyze the TcpD and TcpE proteins in C. perfringens, functional hemagglutinin (HA)-tagged derivatives were constructed. Western blots showed that TcpD and TcpE localized to the cell envelope fraction independently of the presence of other pCW3-encoded proteins. Finally, examination of the subcellular localization of TcpD and TcpE by immunofluorescence showed that these proteins were concentrated at both poles of C. perfringens donor cells, where they are postulated to form essential components of the multiprotein complex that comprises the transfer apparatus. Conjugative transfer of plasmid DNA is an important process that contributes to bacterial genome plasticity and adaption, particularly the spread of antibiotic resistance and virulence genes (1, 2). The translocation of a conjugative plasmid relies on the coupling protein, the relaxosome complex, and a type IV secretion system (T4SS), known as the mating-pair formation (Mpf) apparatus (1). For conjugation systems in Gram-negative bacteria, structural resolution of the outer membrane core complex and the inner membrane complex of the T4SS, as well as information about the pathway of DNA translocation across the T4SS in the donor cell, has been elucidated (3-11). Less is known about conjugation systems in Gram-positive bacteria, with our current understanding based primarily on comparisons to those in Gramnegative bacteria and with the systems in Gram-positive bacteria proposed to involve a "minimized" T4SS (3, 12-18).The Gram-positive, anaerobic pathogen Clostridium perfringens carries many disease-mediating toxin genes and antibiotic resistance genes on a unique family of large plasmids that have large regions of sequence identity (19)(20)(21)(22). Most of these plasmids carry the novel tcp conjugation locus (20, 23). The tcp locus has been identified on all known conjugative plasmids in C. perfringens, and proteins encoded by this locus have been shown to be required for conjugative transfer of the paradigm C. perfringens conjugative plasmid, pCW3 (20,(23)(24)(25)(26). The presence of the tcp genes on so many of these toxin plasmids suggests that the transfer of toxin genes by a shared conjugation mechanism in C. perfringens is important in disease dissemination. To this effect, several of these toxin plasmids have been shown experimentally to be conjugative (19,27,28).M...

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“…Recent studies on various ICEs of Firmicutes, carrying related conjugation modules, encoding a MOB T relaxase related to RCR replicases of plasmids (Guglielmini et al, 2014), including ICESt3 (Carraro et al, 2011), RD2 from Streptococcus suis MGAS6180 (Sitkiewicz et al, 2011) and ICEBs1 (Lee et al, 2010), strongly supported their intracellular RCR. No replication module, per se, carried by these ICEs could be identified (Bellanger et al, 2014;Carraro & Burrus, 2014c).…”

Section: Discussionmentioning

confidence: 94%

Plasmid-like replication of a minimal streptococcal integrative and conjugative element

et al. 2016

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Integrative and conjugative elements (ICEs) are mobile genetic elements encoding their own excision from a replicon of their bacterial host, transfer by conjugation to a recipient bacterium and reintegration for maintenance. The conjugation, recombination and regulation modules of ICEs of the ICESt3 family are grouped together in a region called the ICE 'core region'. In addition to this core region, elements belonging to this family carry a highly variable region including cargo genes that could be involved in bacterial adaptation or in the maintenance of the element. Although ICEs are a major class of mobile elements through bacterial genomes, the functionality of an element encoding only its excision, transfer, integration and regulation has never been demonstrated experimentally. We engineered MiniICESt3, an artificial ICE derived from ICESt3, devoid of its cargo genes and thus only harbouring the core region. The functionality of this minimal element was assessed. MiniICESt3 was found to be able to excise at a rate of 3.1 %, transfer with a frequency of 1.0610 25 transconjugants per donor cell and stably maintain by site-specific integration into the 39 end of the fda gene, the same as ICESt3. Furthermore, MiniICESt3 was found in ,10 copies per chromosome, this multicopy state likely contributing to its stability for .100 generations even in the absence of selection. Therefore, although ICEs were primarily assumed to only replicate along with the chromosome, our results uncovered extrachromosomal rolling-circle replicating plasmid-like forms of MiniICESt3.

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Key components of the eight classes of type IV secretion systems involved in bacterial conjugation or protein secretion

Cited by 191 publications

References 91 publications

The Genomic Diversification of the Whole Acinetobacter Genus: Origins, Mechanisms, and Consequences

The Genomic Diversification of the Whole Acinetobacter Genus: Origins, Mechanisms, and Consequences

Two Novel Membrane Proteins, TcpD and TcpE, Are Essential for Conjugative Transfer of pCW3 in Clostridium perfringens

Plasmid-like replication of a minimal streptococcal integrative and conjugative element

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