Adhesion of glucosyltransferase phase variants to Streptococcus gordonii bacterium-glucan substrata may involve lipoteichoic acid

Growing Streptococcus gordonii Spp⁺ phase variants, which have normal levels of glucosyltransferase (GTF) activity, use sucrose to promote their accumulation on surfaces by forming a cohesive bacterium-insoluble glucan polymer mass (BPM). Spp^- phase variants, which have lower levels of GTF activity, do not form BPMs and do not remain in BPMs formed by Spp⁺ cells when grown in mixed cultures. To test the hypothesis that segregation of attached Spp⁺ and unattached Spp^- cells was due to differences in adhesiveness, adhesion between washed, [³H]thymidine-labeled cells and preformed BPM substrata was measured. Unexpectedly, the results showed that cells of both phenotypes, as well as GTF-negative cells, attached equally well to preformed BPMs, indicating that attachment to BPMs was independent of cell surface GTF activity. Initial characterization of this binding interaction suggested that a protease-sensitive component on the washed cells may be binding to lipoteichoic acids sequestered in the BPM, since exogenous lipoteichoic acid inhibited adhesion. Surprisingly, the adhesion of both Spp⁺ and Spp^- cells was markedly inhibited in the presence of sucrose, which also released lipoteichoic acid from the BPM. These in vitro findings suggest that, in vivo, sucrose and lipoteichoic acid may modify dental plaque development by enhancing or inhibiting the attachment of additional bacteria.