Regulation of PI-2b Pilus Expression in Hypervirulent Streptococcus agalactiae ST-17 BM110.
The widely spread Streptococcus agalactiae (also known as Group B Streptococcus, GBS) "hypervirulent" ST17 clone is strongly associated with neonatal meningitis. The PI-2b locus is mainly found in ST17 strains but is also present in a few non ST17 human isolates such as the ST-7 prototype...
| Main Authors: | , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Public Library of Science (PLoS)
2017-01-01
|
| Series: | PLoS ONE |
| Online Access: | http://europepmc.org/articles/PMC5249243?pdf=render |
| _version_ | 1811273246685790208 |
|---|---|
| author | Bruno Périchon Noémi Szili Laurence du Merle Isabelle Rosinski-Chupin Myriam Gominet Samuel Bellais Claire Poyart Patrick Trieu-Cuot Shaynoor Dramsi |
| author_facet | Bruno Périchon Noémi Szili Laurence du Merle Isabelle Rosinski-Chupin Myriam Gominet Samuel Bellais Claire Poyart Patrick Trieu-Cuot Shaynoor Dramsi |
| author_sort | Bruno Périchon |
| collection | DOAJ |
| description | The widely spread Streptococcus agalactiae (also known as Group B Streptococcus, GBS) "hypervirulent" ST17 clone is strongly associated with neonatal meningitis. The PI-2b locus is mainly found in ST17 strains but is also present in a few non ST17 human isolates such as the ST-7 prototype strain A909. Here, we analysed the expression of the PI-2b pilus in the ST17 strain BM110 as compared to the non ST17 A909. Comparative genome analyses revealed the presence of a 43-base pair (bp) hairpin-like structure in the upstream region of PI-2b operon in all 26 ST17 genomes, which was absent in the 8 non-ST17 strains carrying the PI-2b locus. Deletion of this 43-bp sequence in strain BM110 resulted in a 3- to 5-fold increased transcription of PI-2b. Characterization of PI-2b promoter region in A909 and BM110 strains was carried out by RNAseq, primer extension, qRT-PCR and transcriptional fusions with gfp as reporter gene. Our results indicate the presence of a single promoter (Ppi2b) with a transcriptional start site (TSS) mapped 37 bases upstream of the start codon of the first PI-2b gene. The large operon of 16 genes located upstream of PI-2b codes for the group B carbohydrate (also known as antigen B), a major constituent of the bacterial cell wall. We showed that the hairpin sequence located between antigen B and PI-2b operons is a transcriptional terminator. In A909, increased expression of PI-2b probably results from read-through transcription from antigen B operon. In addition, we showed that an extended 5' promoter region is required for maximal transcription of gfp as a reporter gene in S. agalactiae from Ppi2b promoter. Gene reporter assays performed in Lactococcus lactis strain NZ9000, a related non-pathogenic Gram-positive species, revealed that GBS-specific regulatory factors are required to drive PI-2b transcription. PI-2b expression is up-regulated in the BM110ΔcovR mutant as compared to the parental BM110 strain, but this effect is probably indirect. Collectively, our results indicate that PI-2b expression is regulated in GBS ST17 strains, which may confer a selective advantage in the human host either by reducing host immune responses and/or increasing their dissemination potential. |
| first_indexed | 2024-04-12T22:55:40Z |
| format | Article |
| id | doaj.art-64adb5379d6541ac9ae7cda0cde337a5 |
| institution | Directory Open Access Journal |
| issn | 1932-6203 |
| language | English |
| last_indexed | 2024-04-12T22:55:40Z |
| publishDate | 2017-01-01 |
| publisher | Public Library of Science (PLoS) |
| record_format | Article |
| series | PLoS ONE |
| spelling | doaj.art-64adb5379d6541ac9ae7cda0cde337a52022-12-22T03:13:12ZengPublic Library of Science (PLoS)PLoS ONE1932-62032017-01-01121e016984010.1371/journal.pone.0169840Regulation of PI-2b Pilus Expression in Hypervirulent Streptococcus agalactiae ST-17 BM110.Bruno PérichonNoémi SziliLaurence du MerleIsabelle Rosinski-ChupinMyriam GominetSamuel BellaisClaire PoyartPatrick Trieu-CuotShaynoor DramsiThe widely spread Streptococcus agalactiae (also known as Group B Streptococcus, GBS) "hypervirulent" ST17 clone is strongly associated with neonatal meningitis. The PI-2b locus is mainly found in ST17 strains but is also present in a few non ST17 human isolates such as the ST-7 prototype strain A909. Here, we analysed the expression of the PI-2b pilus in the ST17 strain BM110 as compared to the non ST17 A909. Comparative genome analyses revealed the presence of a 43-base pair (bp) hairpin-like structure in the upstream region of PI-2b operon in all 26 ST17 genomes, which was absent in the 8 non-ST17 strains carrying the PI-2b locus. Deletion of this 43-bp sequence in strain BM110 resulted in a 3- to 5-fold increased transcription of PI-2b. Characterization of PI-2b promoter region in A909 and BM110 strains was carried out by RNAseq, primer extension, qRT-PCR and transcriptional fusions with gfp as reporter gene. Our results indicate the presence of a single promoter (Ppi2b) with a transcriptional start site (TSS) mapped 37 bases upstream of the start codon of the first PI-2b gene. The large operon of 16 genes located upstream of PI-2b codes for the group B carbohydrate (also known as antigen B), a major constituent of the bacterial cell wall. We showed that the hairpin sequence located between antigen B and PI-2b operons is a transcriptional terminator. In A909, increased expression of PI-2b probably results from read-through transcription from antigen B operon. In addition, we showed that an extended 5' promoter region is required for maximal transcription of gfp as a reporter gene in S. agalactiae from Ppi2b promoter. Gene reporter assays performed in Lactococcus lactis strain NZ9000, a related non-pathogenic Gram-positive species, revealed that GBS-specific regulatory factors are required to drive PI-2b transcription. PI-2b expression is up-regulated in the BM110ΔcovR mutant as compared to the parental BM110 strain, but this effect is probably indirect. Collectively, our results indicate that PI-2b expression is regulated in GBS ST17 strains, which may confer a selective advantage in the human host either by reducing host immune responses and/or increasing their dissemination potential.http://europepmc.org/articles/PMC5249243?pdf=render |
| spellingShingle | Bruno Périchon Noémi Szili Laurence du Merle Isabelle Rosinski-Chupin Myriam Gominet Samuel Bellais Claire Poyart Patrick Trieu-Cuot Shaynoor Dramsi Regulation of PI-2b Pilus Expression in Hypervirulent Streptococcus agalactiae ST-17 BM110. PLoS ONE |
| title | Regulation of PI-2b Pilus Expression in Hypervirulent Streptococcus agalactiae ST-17 BM110. |
| title_full | Regulation of PI-2b Pilus Expression in Hypervirulent Streptococcus agalactiae ST-17 BM110. |
| title_fullStr | Regulation of PI-2b Pilus Expression in Hypervirulent Streptococcus agalactiae ST-17 BM110. |
| title_full_unstemmed | Regulation of PI-2b Pilus Expression in Hypervirulent Streptococcus agalactiae ST-17 BM110. |
| title_short | Regulation of PI-2b Pilus Expression in Hypervirulent Streptococcus agalactiae ST-17 BM110. |
| title_sort | regulation of pi 2b pilus expression in hypervirulent streptococcus agalactiae st 17 bm110 |
| url | http://europepmc.org/articles/PMC5249243?pdf=render |
| work_keys_str_mv | AT brunoperichon regulationofpi2bpilusexpressioninhypervirulentstreptococcusagalactiaest17bm110 AT noemiszili regulationofpi2bpilusexpressioninhypervirulentstreptococcusagalactiaest17bm110 AT laurencedumerle regulationofpi2bpilusexpressioninhypervirulentstreptococcusagalactiaest17bm110 AT isabellerosinskichupin regulationofpi2bpilusexpressioninhypervirulentstreptococcusagalactiaest17bm110 AT myriamgominet regulationofpi2bpilusexpressioninhypervirulentstreptococcusagalactiaest17bm110 AT samuelbellais regulationofpi2bpilusexpressioninhypervirulentstreptococcusagalactiaest17bm110 AT clairepoyart regulationofpi2bpilusexpressioninhypervirulentstreptococcusagalactiaest17bm110 AT patricktrieucuot regulationofpi2bpilusexpressioninhypervirulentstreptococcusagalactiaest17bm110 AT shaynoordramsi regulationofpi2bpilusexpressioninhypervirulentstreptococcusagalactiaest17bm110 |