Expression and Functional Properties of the Streptococcus intermedius Surface Protein Antigen I/II

Abstract

Streptococcus intermedius is associated with deep-seated purulent infections. In this study, we investigated expression and functional activities of antigen I/II in S. intermedius. The S. intermedius antigen I/II appeared to be cell surface associated, with a molecular mass of approximately 160 kDa. Northern blotting indicated that the S. intermedius NCTC 11324 antigen I/II gene was transcribed as a monocistronic message. Maximum expression was seen during the early exponential phase. Insertional inactivation of the antigen I/II gene resulted in reduced hydrophobicity during early exponential phase, whereas no effect was detected during midand late exponential phases. Binding to human fibronectin and laminin was reduced in the isogenic mutant, whereas binding to human collagen types I and IV and to rat collagen type I was not significant for either the wild type or the mutant. Compared to the wild type, the capacity of the isogenic mutant to induce interleukin 8 (IL-8) release by THP-1 monocytic cells was significantly reduced. The results indicate that the S. intermedius antigen I/II is involved in adhesion to human receptors and in IL-8 induction.Streptococcus intermedius belongs to the anginosus group of streptococci. Members of this group are residents of the oral cavity and gastrointestinal and urogenital tracts but are also associated with suppurative infections at various clinical sites (17,39,49). S. intermedius shows tropism for infections of the brain and liver (49). Like other oral streptococci, S. intermedius may be implicated as a causative agent of infective endocarditis (11,39,49). For both abscesses and infective endocarditis, molecular interactions with host components represent presumptive virulence factors (2, 51).Bacterial interactions with host components are most often associated with surface proteins. The oral streptococci express a family of structurally and antigenically related surface proteins termed antigen I/II. These proteins have received a variety of names according to the strains or species in which they were identified, such as antigen B (40), Sr (35), I/II (20), and PAc (37) from Streptococcus mutans; SpaA from Streptococcus sobrinus (25, 45); and SspA and SspB from two tandemly arranged genes in Streptococcus gordonii (7). Multifunctional activities are attributed to the antigen I/II family, i.e., binding to soluble extracellular matrix glycoproteins (41) and to host cell receptors (42, 47), coaggregation with other microorganisms (4, 15, 24), interactions with salivary glycoproteins (3,9,12,19,21,27,36), and activation of monocytic cells (1,5,6). Members of the antigen I/II family may, however, exhibit functional species specificity. Differences in antigen I/II binding properties, mechanisms, and affinities have, for instance, been described for S. gordonii and S. mutans (18). Enzyme-linked immunosorbent assays (32), DNA hybridization studies (30), and homologous PCR-amplified sequences (6, 30) indicate that the anginosus group of streptococci also expresses an antigen I/II-l...

Biofilm Mode of Growth of Streptococcus intermedius Favored by a Competence-Stimulating Signaling Peptide

“…In our study we investigated directly the role of the CSP signal in biofilm formation and competence development of the wildtype strain. We found that the respective synthetic CSPs favored the biofilm mode of growth for both S. intermedius and S. mutans, and we confirmed the role of CSP in S. intermedius competence development (9,19).…”

“…Initiation of a QS response during competence development is influenced by environmental conditions. For S. intermedius, conditions that support endogenous induction of competence development have been described (9,19). It appears, however, that the growth-dependent requirements for spontaneous competence can in several instances be overcome by addition of synthetic CSP (8).…”

“…After a 24-h incubation, transformants were selected by growth on THB agar plates containing the selective antibiotic. Biofilm cells grown in THB supplemented with horse serum (9,19) were included as positive controls. Cells grown in THB supplemented with horse serum showed spontaneous competence development, with a transformation yield of 40 transformants/ml, whereas growth in TSB resulted in no transformants.…”

Intermolecular Forces and Enthalpies in the Adhesion of Streptococcus mutans and an Antigen I/II-Deficient Mutant to Laminin Films

“…However, upon dental treatment the organism may enter the bloodstream, which can result in infectious endocarditis. Most oral streptococci, including S. mutans, Streptococcus sobrinus, Streptococcus gordonii, and Streptococcus intermedius, express a family of structurally and antigenically related surface proteins termed antigen I/II with molecular masses ranging from 160 to 215 kDa (13,21,23,30,32). From the N terminus, the polypeptide has an aminoterminal signal peptide, an alanine-rich repeat unit, a variable region, a proline-rich repeat region, a carboxy-terminal walland membrane-spanning region, and an LPXTG wall anchor motif (19,38).…”

Streptococcus pyogenesGlycoprotein-Binding Strepadhesin Activity Is Mediated by a Surface-Associated Carbohydrate-Degrading Enzyme, Pullulanase

“…The apparently broad binding specificity toward different glycoproteins is, however, not unusual among bacterial adhesins. For example, antigen I and II adhesins of oral streptococci mediate binding to a wide variety of molecules, such as salivary agglutinin, collagen, laminin, and fibronectin, and also to other microorganisms of the oral cavity without any apparent specificity toward a single molecular determinant (28,36,43,44,50). The increased amount of streptococcal pullulanase on the surface of the Rgg-deficient strain NZ131rgg and the increased strepadhesin activity could be due to at least two cellular mechanisms.…”