Differential metabolic activity by dental plaque bacteria in association with two preparations of MUC5B mucins in solution and in biofilms.

Salivary mucin, MUC5B, is an oligomeric glycoprotein, heterogeneous in size and with a diverse repertoire of oligosaccharides, which differ in composition and charge. Since complex salivary glycoproteins are considered to be the major source of nutrients for the oral supragingival microbiota, the major aim of the current study was to determine whether different preparations of non-denatured MUC5B could be isolated exhibiting different biological properties in relation to the microflora associated with the surfaces of the oral cavity. Two preparations, solMUC5B and gelMUC5B, were isolated by density-gradient centrifugation and were shown to have different buoyant densities, carbohydrate content and surface-adsorbing characteristics.

Oral bacteria in biofilms exhibit slow reactivation from nutrient deprivation.

The ability of oral bacteria to enter a non-growing state is believed to be an important mechanism for survival in the starved micro-environments of the oral cavity. In this study, we examined the reactivation of nutrient-deprived cells of two oral bacteria in biofilms, Streptococcus anginosus and Lactobacillus salivarius. Non-growing cells were generated by incubation in 10 mM potassium phosphate buffer for 24 h and the results were compared to those of planktonic cultures.

Multiple stress responses in Streptococcus mutans and the induction of general and stress-specific proteins.

The authors have previously demonstrated that Streptococcus mutans shows an exponential-phase acid-tolerance response following an acid shock from pH 7.5 to 5.5 that enhances survival at pH 3.

Streptococcus mutans ffh, a gene encoding a homologue of the 54 kDa subunit of the signal recognition particle, is involved in resistance to acid stress.

The ability of Streptococcus mutans, a bacterial pathogen associated with dental caries, to tolerate rapid drops in plaque pH (acidurance), is considered an important virulence factor. To study this trait, Tn917 mutants of S. mutans strain JH1005 which display acid sensitivity have been isolated and partially characterized.