The Relationship between Coaggregation Properties and Surface Structures ofBacteroides intermedius

Abstract

Seven out of 20 Bacteroides intermedius isolates coaggregated with two Actinomyces viscosus and four A. naeslundii strains. None coaggregated with seven other strains representing five Gram-positive oral species. Coaggregating ability was unrelated to B. intermedius serogroup, surface hydrophobicity, or morphology of fibrils or ruthenium red (RR) staining layers. The coaggregation adhesin on B. interrnedius isolates recognising A. viscosus and A. naeslundii was unaffected by serum, saliva, sugars and Congo red. It was inactivated by NaIO 4 , heat, proteinase K and, in 4/7 isolates, by trypsin but not by heat-inactivated enzymes. Coaggregation adhesins on serogroup I isolates were resistant to trypsin, and were less susceptible than those on other strains to heat and proteinase K. Cell surface hydrophobicity was unaltered by NaIO 4 and trypsin. RR staining matrices and capsules (detected by staining with Indian ink) were unaffected by trypsin, but NaIO 4 removed both. Capsules and fibrils were removed at different times by NaIO 4 and were therefore different structures. Coaggregating ability disappeared with removal of fibrils indicating the adhesin was associated with the fibrillar layer. All B. intermedius isolates carried two types of fibril. One was removed by trypsin treatment but was not involved in coaggregation. The other was not removed by trypsin or proteinase K. The proteinase K and heat-inactivatable coaggregation adhesin may be a non-structural component of these fibrils. Keywords: B. intermedius ; Coaggregation; Adhesins; Actiriomyces spp. ; Ultrastructure; Fibrils; Ruthenium red; Capsules; Hydrophobicity.