title: ThesilLocus inStreptococcusAnginosus Group: Interspecies Competition and a Hotspot of Genetic Diversity.
abstract: TheStreptococcusInvasion Locus (Sil) was first described inStreptococcus pyogenesandStreptococcus pneumoniae, where it has been implicated in virulence. The two-component peptide signaling system consists of the SilA response regulator and SilB histidine kinase along with the SilCR signaling peptide and SilD/E export/processing proteins. The presence of an associated bacteriocin region suggests this system may play a role in competitive interactions with other microbes. Comparative analysis of 42StreptococcusAnginosus/Milleri Group (SAG) genomes reveals this to be a hot spot for genomic variability. A cluster of bacteriocin/immunity genes is found adjacent to thesilsystem in most SAG isolates (typically 6-10 per strain). In addition, there were two distinct SilCR peptides identified in this group, denoted here as SilCRSAG-Aand SilCRSAG-B, with corresponding alleles insilB. Our analysis of the 42silloci showed that SilCRSAG-Ais only found inStreptococcus intermediuswhile all three species can carry SilCRSAG-B. InS. intermediusB196, a putative SilA operator is located upstream of bacteriocin gene clusters, implicating thesilsystem in regulation of microbe-microbe interactions at mucosal surfaces where the group resides. We demonstrate thatS. intermediusB196 responds to its cognate SilCRSAG-A, and, less effectively, to SilCRSAG-Breleased by other Anginosus group members, to produce putative bacteriocins and inhibit the growth of a sensitive strain ofS. constellatus.
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, HamiltonON, Canada; Farncombe Family Digestive Health Research Institute, McMaster University, HamiltonON, Canada.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Mendonca
authors.affiliation: Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton ON, Canada.
authors.forename: Jake C
authors.initials: JC
authors.lastname: Szamosi
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, HamiltonON, Canada; Farncombe Family Digestive Health Research Institute, McMaster University, HamiltonON, Canada.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Lacroix
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, HamiltonON, Canada; Farncombe Family Digestive Health Research Institute, McMaster University, HamiltonON, Canada.
authors.forename: Michelle E
authors.initials: ME
authors.lastname: Fontes
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, HamiltonON, Canada; Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, HamiltonON, Canada.
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Bowdish
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, HamiltonON, Canada; Farncombe Family Digestive Health Research Institute, McMaster University, HamiltonON, Canada; Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, HamiltonON, Canada; Department of Medicine, McMaster University, HamiltonON, Canada.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Surette
keywords: Streptococcus Anginosus Group; Streptococcus Milleri Group; bacteriocins; cell–cell signaling; quorum sensing; sil system