title: A collagen-binding adhesin, Acb, and ten other putative MSCRAMM and pilus family proteins of Streptococcus gallolyticus subsp. gallolyticus (Streptococcus bovis Group, biotype I).
abstract: Members of the Streptococcus bovis group are important causes of endocarditis. However, factors associated with their pathogenicity, such as adhesins, remain uncharacterized. We recently demonstrated that endocarditis-derived Streptococcus gallolyticus subsp. gallolyticus isolates frequently adhere to extracellular matrix (ECM) proteins. Here, we generated a draft genome sequence of an ECM protein-adherent S. gallolyticus subsp. gallolyticus strain and found, by genome-wide analyses, 11 predicted LPXTG-type cell wall-anchored proteins with characteristics of MSCRAMMs, including a modular architecture of domains predicted to adopt immunoglobulin (Ig)-like folding. A recombinant segment of one of these, Acb, showed high-affinity binding to immobilized collagen, and cell surface expression of Acb correlated with the presence of acb and collagen adherence of isolates. Three of the 11 proteins have similarities to major pilus subunits and are organized in separate clusters, each including a second Ig-fold-containing MSCRAMM and a class C sortase, suggesting that the sequenced strain encodes three distinct types of pili. Reverse transcription-PCR demonstrated that all three genes of one cluster, acb-sbs7-srtC1, are cotranscribed, consistent with pilus operons of other gram-positive bacteria. Further analysis detected expression of all 11 genes in cells grown to mid to late exponential growth phases. Wide distribution of 9 of the 11 genes was observed among S. gallolyticus subsp. gallolyticus isolates with fewer genes present in other S. bovis group species/subspecies. The high prevalence of genes encoding putative MSCRAMMs and pili, including a collagen-binding MSCRAMM, among S. gallolyticus subsp. gallolyticus isolates may play an important role in the predominance of this subspecies in S. bovis endocarditis.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas 77030, USA.
authors.forename: Jouko
authors.initials: J
authors.lastname: Sillanpää
authors.forename: Sreedhar R
authors.initials: SR
authors.lastname: Nallapareddy
authors.forename: Xiang
authors.initials: X
authors.lastname: Qin
authors.forename: Kavindra V
authors.initials: KV
authors.lastname: Singh
authors.forename: Donna M
authors.initials: DM
authors.lastname: Muzny
authors.forename: Christie L
authors.initials: CL
authors.lastname: Kovar
authors.forename: Lynne V
authors.initials: LV
authors.lastname: Nazareth
authors.forename: Richard A
authors.initials: RA
authors.lastname: Gibbs
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Ferraro
authors.forename: James M
authors.initials: JM
authors.lastname: Steckelberg
authors.forename: George M
authors.initials: GM
authors.lastname: Weinstock
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Murray
mesh_terms: D018829:Adhesins, Bacterial / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D016680:Genome, Bacterial; D005810:Multigene Family; D013291:Streptococcus / Q000145:classification / Q000235:genetics / Q000378:metabolism*
chemical_list: D018829:Adhesins, Bacterial