Streptococcal group B integrative and mobilizable element IMESag-rpsI encodes a functional relaxase involved in its transfer
Streptococcus agalactiae or Group B Streptococcus (GBS) are opportunistic bacteria that can cause lethal sepsis in children and immuno-compromised patients. Their genome is a reservoir of mobile genetic elements that can be horizontally transferred. Among them, integrative and conjugative elements (...
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| Format: | Article |
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The Royal Society
2016-01-01
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| Series: | Open Biology |
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| Online Access: | https://royalsocietypublishing.org/doi/pdf/10.1098/rsob.160084 |
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| author | Fabian Lorenzo-Diaz Cris Fernández-Lopez Pierre-Emmanuel Douarre Adrian Baez-Ortega Carlos Flores Philippe Glaser Manuel Espinosa |
| author_facet | Fabian Lorenzo-Diaz Cris Fernández-Lopez Pierre-Emmanuel Douarre Adrian Baez-Ortega Carlos Flores Philippe Glaser Manuel Espinosa |
| author_sort | Fabian Lorenzo-Diaz |
| collection | DOAJ |
| description | Streptococcus agalactiae or Group B Streptococcus (GBS) are opportunistic bacteria that can cause lethal sepsis in children and immuno-compromised patients. Their genome is a reservoir of mobile genetic elements that can be horizontally transferred. Among them, integrative and conjugative elements (ICEs) and the smaller integrative and mobilizable elements (IMEs) primarily reside in the bacterial chromosome, yet have the ability to be transferred between cells by conjugation. ICEs and IMEs are therefore a source of genetic variability that participates in the spread of antibiotic resistance. Although IMEs seem to be the most prevalent class of elements transferable by conjugation, they are poorly known. Here, we have studied a GBS-IME, termed IMESag-rpsI, which is widely distributed in GBS despite not carrying any apparent virulence trait. Analyses of 240 whole genomes showed that IMESag-rpsI is present in approximately 47% of the genomes, has a roughly constant size (approx. 9 kb) and is always integrated at a single location, the 3′-end of the gene encoding the ribosomal protein S9 (rpsI). Based on their genetic variation, several IMESag-rpsI types were defined (A–J) and classified in clonal complexes (CCs). CC1 was the most populated by IMESag-rpsI (more than 95%), mostly of type-A (71%). One CC1 strain (S. agalactiae HRC) was deep-sequenced to understand the rationale underlying type-A IMESag-rpsI enrichment in GBS. Thirteen open reading frames were identified, one of them encoding a protein (MobSag) belonging to the broadly distributed family of relaxases MOBV1. Protein MobSag was purified and, by a newly developed method, shown to cleave DNA at a specific dinucleotide. The S. agalactiae HRC-IMESag-rpsI is able to excise from the chromosome, as shown by the presence of circular intermediates, and it harbours a fully functional mobilization module. Further, the mobSag gene encoded by this mobile element is able to promote plasmid transfer among pneumococcal strains, suggesting that MobSag facilitates the spread of IMESag-rpsI and that this spread would explain the presence of the same IMESag-rpsI type in GBS strains belonging to different CCs. |
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| institution | Directory Open Access Journal |
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| language | English |
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| publishDate | 2016-01-01 |
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| spelling | doaj.art-50469300873f4fa193649314daff84942022-12-21T19:50:30ZengThe Royal SocietyOpen Biology2046-24412016-01-0161010.1098/rsob.160084160084Streptococcal group B integrative and mobilizable element IMESag-rpsI encodes a functional relaxase involved in its transferFabian Lorenzo-DiazCris Fernández-LopezPierre-Emmanuel DouarreAdrian Baez-OrtegaCarlos FloresPhilippe GlaserManuel EspinosaStreptococcus agalactiae or Group B Streptococcus (GBS) are opportunistic bacteria that can cause lethal sepsis in children and immuno-compromised patients. Their genome is a reservoir of mobile genetic elements that can be horizontally transferred. Among them, integrative and conjugative elements (ICEs) and the smaller integrative and mobilizable elements (IMEs) primarily reside in the bacterial chromosome, yet have the ability to be transferred between cells by conjugation. ICEs and IMEs are therefore a source of genetic variability that participates in the spread of antibiotic resistance. Although IMEs seem to be the most prevalent class of elements transferable by conjugation, they are poorly known. Here, we have studied a GBS-IME, termed IMESag-rpsI, which is widely distributed in GBS despite not carrying any apparent virulence trait. Analyses of 240 whole genomes showed that IMESag-rpsI is present in approximately 47% of the genomes, has a roughly constant size (approx. 9 kb) and is always integrated at a single location, the 3′-end of the gene encoding the ribosomal protein S9 (rpsI). Based on their genetic variation, several IMESag-rpsI types were defined (A–J) and classified in clonal complexes (CCs). CC1 was the most populated by IMESag-rpsI (more than 95%), mostly of type-A (71%). One CC1 strain (S. agalactiae HRC) was deep-sequenced to understand the rationale underlying type-A IMESag-rpsI enrichment in GBS. Thirteen open reading frames were identified, one of them encoding a protein (MobSag) belonging to the broadly distributed family of relaxases MOBV1. Protein MobSag was purified and, by a newly developed method, shown to cleave DNA at a specific dinucleotide. The S. agalactiae HRC-IMESag-rpsI is able to excise from the chromosome, as shown by the presence of circular intermediates, and it harbours a fully functional mobilization module. Further, the mobSag gene encoded by this mobile element is able to promote plasmid transfer among pneumococcal strains, suggesting that MobSag facilitates the spread of IMESag-rpsI and that this spread would explain the presence of the same IMESag-rpsI type in GBS strains belonging to different CCs.https://royalsocietypublishing.org/doi/pdf/10.1098/rsob.160084conjugationhorizontal gene transferintegrative and mobilizable elements mobilizationrelaxasesstreptococcus |
| spellingShingle | Fabian Lorenzo-Diaz Cris Fernández-Lopez Pierre-Emmanuel Douarre Adrian Baez-Ortega Carlos Flores Philippe Glaser Manuel Espinosa Streptococcal group B integrative and mobilizable element IMESag-rpsI encodes a functional relaxase involved in its transfer Open Biology conjugation horizontal gene transfer integrative and mobilizable elements mobilization relaxases streptococcus |
| title | Streptococcal group B integrative and mobilizable element IMESag-rpsI encodes a functional relaxase involved in its transfer |
| title_full | Streptococcal group B integrative and mobilizable element IMESag-rpsI encodes a functional relaxase involved in its transfer |
| title_fullStr | Streptococcal group B integrative and mobilizable element IMESag-rpsI encodes a functional relaxase involved in its transfer |
| title_full_unstemmed | Streptococcal group B integrative and mobilizable element IMESag-rpsI encodes a functional relaxase involved in its transfer |
| title_short | Streptococcal group B integrative and mobilizable element IMESag-rpsI encodes a functional relaxase involved in its transfer |
| title_sort | streptococcal group b integrative and mobilizable element imesag rpsi encodes a functional relaxase involved in its transfer |
| topic | conjugation horizontal gene transfer integrative and mobilizable elements mobilization relaxases streptococcus |
| url | https://royalsocietypublishing.org/doi/pdf/10.1098/rsob.160084 |
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