The Function and Distribution of Different Fimbriae on Strains of Actinomyces viscosus and Actinomyces naeslundii

Actinomyces viscosus and Actinomyces naeslundii differ in their abilities to colonize tooth and epithelial surfaces. These differences appear to be associated with the distribution of different fimbriae on the two species and with the distinct adherence-related functions of these structures.</jats:p

Actinomyces Adsorption Mediated by Type-1 Fimbriae

Monospecific antibody against the type-1 fimbriae of Actinomyces viscosus T14V reacted with 12 strains of A. viscosus (serotype 2), 12 strains of A. naeslundii (serotype 2 or serotype 3), but not with 11 serotype 1 strains of A. naeslundii. All strains positive for the type-1 fimbrial antigen adsorbed strongly to saliva-treated hydroxyapatite, and in many instances (18 of 24 strains) this interaction was inhibited by the monospecific antibody. These findings strongly suggest that only those strains of actinomyces which possess type-1 fimbriae adhere to the tooth surfaces, and that these fimbriae constitute the principal adhesin involved in this interaction. </jats:p

ADHESION OF MUTANS STREPTOCOCCI TO GLASS WITH AND WITHOUT A SALIVARY COATING AS STUDIED IN A PARALLEL-PLATE FLOW CHAMBER

Deposition and adhesion to glass with and without a salivary coating in a parallel-plate flow chamber were studied with four strains of mutans streptococci. Stationary-state adhesion of the strains to uncoated glass ranged from 0.3 x 10(6) cm-2 (Streptococcus rattus HG218) to 12.7 x 10(6) cm-2 (Streptococcus sobrinus HG1025) and generally decreased after saliva coating of the glass. The poor adhesion found for S. rattus HG218 to both uncoated and saliva-coated glass could be due to its relatively high negative surface-charge. Deposition efficiencies of all strains were greater-than-or-equal-to 1 for uncoated glass and decreased greatly after saliva coating of the glass. Possibly, adhesion to a saliva coating is less efficient and more time-consuming than that to uncoated glass, because stereochemical groups in the pellicle and on the cell surfaces may have to re-arrange before an effective interaction can occur. Desorption rates, measured 1000 s and 5000 s after the start of an experiment, decreased by a factor of ten upon a five-fold increase in contact time, indicative of a two-phase adhesion process. Of the four strains studied, only Streptococcus cricetus HG737 showed a minor positive cooperativity on saliva-coated glass, possibly mediated by surface appendages observed by transmission electron microscopy on negatively-stained cells. Retention of adhering bacteria was strain-dependent on uncoated glass, but was identical for all strains on saliva-coated glass, which suggests that the structure and composition of the pellicle may be more important with respect to the retention of adhering cells than the cell-surface properties themselves

Coaggregation between Rhodococcus

In this study, coaggregation interactions between Rhodococcus and Acinetobacter strains isolated from food-processing surfaces were characterized. Rhodococcus sp. strain MF3727 formed intrageneric coaggregates with Rhodococcus sp. strain MF3803 and intergeneric coaggregates with 2 strains of Acinetobacter calcoaceticus (MF3293, MF3627). Stronger coaggregation between A. calcoaceticus MF3727 and Rhodococcus sp. MF3293 was observed after growth in batch culture at 30 °C than at 20 °C, after growth in tryptic soy broth than in liquid R2A medium, and between cells in exponential and early stationary phases than cells in late stationary phase. The coaggregation ability of Rhodococcus sp. MF3727 was maintained even after heat and Proteinase K treatment, suggesting its ability to coaggregate was protein independent whereas the coaggregation determinants of the other strains involved proteinaceous cell-surface-associated polymers. Coaggregation was stable at pH 5-9. The mechanisms of coaggregation among Acinetobacter and Rhodococcus strains bare similarity to those displayed by coaggregating bacteria of oral and freshwater origin, with respect to binding between proteinaceous and nonproteinaceous determinants and the effect of environmental factors on coaggregation. Coaggregation may contribute to biofilm formation on industrial food surfaces, protecting bacteria against cleaning and disinfection.submittedVersio