title: Adaptive response of Group B streptococcus to high glucose conditions: new insights on the CovRS regulation network.
abstract: Although the contribution of carbohydrate catabolism to bacterial colonization and infection is well recognized, the transcriptional changes during these processes are still unknown. In this study, we have performed comparative global gene expression analysis of GBS in sugar-free versus high glucose milieu. The analysis revealed a differential expression of genes involved in metabolism, transport and host-pathogen interaction. Many of them appeared to be among the genes previously reported to be controlled by the CovRS two-component system. Indeed, the transcription profile of a ΔcovRS strain grown in high-glucose conditions was profoundly affected. In particular, of the total genes described to be regulated by glucose, ∼27% were under CovRS control with a functional role in protein synthesis, transport, energy metabolism and regulation. Among the CovRS dependent genes, we found bibA, a recently characterized adhesin involved in bacterial serum resistance and here reported to be down-regulated by glucose. ChIP analysis revealed that in the presence of glucose, CovR binds bibA promoter in vivo, suggesting that CovR may act as a negative regulator or a repressor. We also demonstrated that, as for other target promoters, chemical phosphorylation of CovR in aspartic acid increases its affinity for the bibA promoter region. The data reported in this study contribute to the understanding of the molecular mechanisms modulating the adaptation of GBS to glucose.
authors.affiliation: Novartis Vaccines and Diagnostics, Siena, Italy.
authors.forename: Benedetta
authors.initials: B
authors.lastname: Di Palo
authors.forename: Valentina
authors.initials: V
authors.lastname: Rippa
authors.forename: Isabella
authors.initials: I
authors.lastname: Santi
authors.forename: Cecilia
authors.initials: C
authors.lastname: Brettoni
authors.forename: Alessandro
authors.initials: A
authors.lastname: Muzzi
authors.forename: Matteo Maria Emiliano
authors.initials: MM
authors.lastname: Metruccio
authors.forename: Renata
authors.initials: R
authors.lastname: Grifantini
authors.forename: John L
authors.initials: JL
authors.lastname: Telford
authors.forename: Silvia Rossi
authors.initials: SR
authors.lastname: Paccani
authors.forename: Marco
authors.initials: M
authors.lastname: Soriani
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D018829:Adhesins, Bacterial / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator; D005947:Glucose / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013292:Streptococcus agalactiae / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D018829:Adhesins, Bacterial; D011994:Recombinant Proteins; D005947:Glucose