ChIP-seq of the response regulator CovR in Group B Streptococcus (GBS)

We report the characterization of the major regulator of virulence gene expression (CovR) in Group B Streptococcus. The ChIP-seq experiments define the binding of CovR on the chromosome of the BM110 strain, a representative of the hypervirulent GBS lineage responsible of neonatal meningitis. Regulatory evolution of CovR signaling was investigated by comparing ChIP-seq done in parallel in a second GBS clinical isolate (NEM316) not belonging to the hypervirulent lineage. In order to define the CovR binding regions along the genome of the GBS, we expressed an ectopic flagged variant of CovR (CovR-3XFLAG) under the control of a anhydrotetracycline (aTc) inducible promoter in a ∆covR background. This functional FLAG-CovR variant was used for ChIP-sequencing with immunoprecipitations done on exponentially growing bacteria in THY + Hepes 50 mM. Two independent replicates were done for each sample (Rep1 and Rep2). CovR-FLAG were induced with 50 and 200 ng/ml aTc in the cultures. The controls are the non-induced condition (no-aTc) and the non-epitope tagged CovR strain (no-TAG). Experiments were done in the BM110 and NEM316 strains.