mRNA transcriptional profiles in Streptococcus thermophilus wild-type strain LMD-9 and 3 mutants deleted for the pptAB, eep and amiCDE genes.

In Gram-positive bacteria, the direct quorum sensing activation pathway involves sensing a autoinducing peptide (AIP) inside the cell after its maturation, export and re-internalization. Once internalized, the AIP interacts with a transcriptional regulator belonging to the RRNPP family. In Streptococcus thermophilus, AIPs are matured by a protease called Eep, exported by an ABC transporter called PptAB, and re-imported by another ABC transporter called Ami. We used a deep sequencing approach (RNAseq) to identify all genes whose expression is controlled by a quorum sensing mechanism involving the three partners PptAB, Eep and Ami. Thus, we studied the mRNA transcriptional profiles in Streptococcus thermophilus strain LMD-9 and 3 mutants deleted for the pptAB, eep and amiCDE genes. The four strains were also deleted for the comR gene in order to get rid off the genes whose expression is controlled by ComR. Indeed, ComR is a RRNPP regulator and its regulon has been already identified. The four strains were grown in a chemically defined medium and cell were harvested at the end of the exponential phase (OD600 1).