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

Abstract

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). Sppphase 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 Sppcells was due to differences in adhesiveness, adhesion between washed, [3lHlthymidine-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 Sppcells 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. 4301 on August 2, 2020 by guest http://iai.asm.org/ Downloaded from 508-514. INFECT. IMMUN. on August 2, 2020 by guest http://iai.asm.org/ Downloaded from

Sucrose‐dependent accumulation of oral streptococci and their adhesion‐defective mutants on saliva‐coated hydroxyapatite

“…These may include interactions of several types; for example, bacterial cell surface components such as glucosyltransferase may interact with water-soluble polymers (14,33). Sucrose is also known to affect complexes between glucans and the hpoteichoic acid or other cell surface amphipathic molecules (5) and to influence accumulation (42). Finally, carbohydrate-inducible genes such as those described in mutans streptococci that are related to ^(/"expression (15) and carbohydrate metabolism (36) may influence properties involved in accumulation.…”

“…Lipoteichoic acid was measured by enzyme-linked immunosorbent assay (ELISA) as previously described (42). Parent and mutant strains were grown anaerobically in FMC medium until cultures reached the same ^520 at the mid-to late-log phase of growth.…”

“…The dialyzed extracts were adsorbed to polyvinyl plates (Dynatech Laboratories, Alexandria, VA) and the lipoteichoic acid detected with polyclonal rabbit antibody specific for the glycerolphosphate moiety of lipoteichoic acid (17), (a gift from R. E. Kessler), horseradish conjugated goat anit-rabbit immunoglobulin (Bio-Rad Laboratories, Richmond, CA) and hydrogen peroxide/TMB (3,3',5,5'tetramethylbenzidine) substrate (Kirkegaard and Perry Laboratories, Gaithersburg, MD). Column-purified lipoteichoic acid from strain Challis (a gift from R. E. Kessler) was used to construct standard curves over the concentration range of 50 ng/ml to 0.8 ng/ ml (42 were calculated from least squares regression analyses.…”

“…Lipoteichoic acid may contribute to the hydrophobicity of oral streptococci and to their adhesive properties (6,29) and has been implicated in S. gordonii accumulation (42). Since the 3 mutant strains were all relatively hydrophilic, cellular lipoteichoic acid concentrations were measured to determine whether this cell surface property was related to the adhesive changes in our mutants.…”

“…Glucan polymers that have been synthesized from dietary sucrose via the bacterial extracellular enzyme glucosyltransferase may facilitate bacterial accumulation. Bacteria may bind directly to the enzyme and its glucan products (8,14,33) or may bind to amphipathic molecules such as lipoteichoic acids that are complexed to glucans (29,42). Although sucrose-associated accumulation mechanisms are best defined for mutans streptococci (24), recent evidence suggests that sucrose and resulting glucan synthesis may be important in the accumulation of 5. gordonii strain Challis (40).…”