Transcriptomic analysis of the major regulator of virulence CovR in Group B Streptococcus strains BM110 and NEM16.

To define the transcriptional response associated to a CovR inactivation we performed RNA-Seq in GBS strains BM110 and NEM316. We used mutants in which CovR is inactivated following a two base-pairs chromosomal substitution (AT->CC) resulting in the translation of a CovRD53A variant unable to be phosphorylated by the histidine kinase CovS. We also used a ∆covR mutant in strain BM110 in which the covR sequence is deleted from the chromosome. We have perfomed two experiments. Th first experiment includes the transcriptomes of BM110 and NEM316 wild-type and the correspondent CovRD53A mutant strains, whom cultures, RNA preparation and sequencing were done in parallel to allow a quantitative comparison. The second experiment includes the transcriptomes of BM110 wild-type and ∆covR mutant. For both experiments, three triplicates were done for each sample and each replicate was done in a different day to take into account the replica biases during statistical analysis.