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...
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doaj-64adb5379d6541ac9ae7cda0cde337a52020-11-25T02:08:33ZengPublic 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 |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Bruno Périchon Noémi Szili Laurence du Merle Isabelle Rosinski-Chupin Myriam Gominet Samuel Bellais Claire Poyart Patrick Trieu-Cuot Shaynoor Dramsi |
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 |
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 |
title |
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_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_sort |
regulation of pi-2b pilus expression in hypervirulent streptococcus agalactiae st-17 bm110. |
publisher |
Public Library of Science (PLoS) |
series |
PLoS ONE |
issn |
1932-6203 |
publishDate |
2017-01-01 |
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. |
url |
http://europepmc.org/articles/PMC5249243?pdf=render |
work_keys_str_mv |
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