Aim We explored in silico and in vitro the complete bacteriocin profile of the oral probiotic Streptococcus oralis subsp. dentisani strain 7746 with the primary objective of providing a descriptive analysis of bacteriocin genomic organization, regulatory context, and transcriptional expression.Methods The recently closed genome of 7746 was subjected to genome mining searches for bacteriocin biosynthetic gene clusters with BAGEL4 and antiSMASH. Orthology conservation analyses were performed to distinguish between bacteriocin-like peptides (Blp) and competence (Com) related peptides. We assessed bacteriocins’ transcription by non-quantitative cross-gene RT-PCR.Results Three new bacteriocin-coding genes were identified, which increased to 14 the number of bacteriocins encoded by S. dentisani 7746. We proved that all 14 identified bacteriocins are transcriptionally expressed. We have assigned names to bacteriocins with unnamed orthologs in other species, proposing the name Denticins (from Denticin A to Denticin H). Our analysis led us to propose a model for competence and bacteriocin regulation in this strain, ruled by complete sets of Com and Blp-like quorum sensing systems.Conclusion Our results suggest that S. dentisani 7746 is the bacterial isolate with the largest repertoire of bacteriocin genes known to date and that part of its blp-like region might have been acquired by horizontal gene transfer from pneumococci.
Revilla-Guarinos et al. (Tue,) studied this question.