Changes in relative transcript amounts caused by ?tprA, ?phrA, double ?tprA ?phrA mutation or the addition of PhrA peptide in Streptococcus pneumoniae

Lantibiotics are highly modified peptides that are part of the bacteriocin family of antimicrobial peptides. We have identified a Phr peptide quorum sensing system (TprA/PhrA) that controls the expression of a lantibiotic gene cluster in the Gram-positive human pathogen, Streptococcus pneumoniae. We have characterized the basic mechanism for a Phr peptide signaling system in S. pneumoniae D39 and found that it induces expression of the lantibiotic genes when pneumococcal cells are at high density in the presence of galactose, a main sugar of the human nasopharynx, a highly competitive microbial environment. In this study we used RNA-seq analysis to examine the changes in relative transcript amounts caused by ?tprA and ?phrA mutations or the addition of the 10-residue synthetic PhrA peptide. These analyses reveal that PhrA peptide addition induces the transcription of a cluster of lantibiotic gene that appear to process and provide immunity to a lantibiotic peptide. In addition, TprA, a transcriptional factor regulated by a Phr peptide, autoregulates its own transcription. Overall design: RNA samples were prepared from a wild-type strain, a wild-type strain treated with PhrA peptide, and three mutant strains. Three independent biological replicates of RNA were prepared for each strain or condition. cDNA libraries were sequenced and the sequencing results were used as the data base for differential expression analysis.