MULTIPLE PHASE VARIATION IN HEMOLYTIC - ADHESIVE AND ANTIGENIC PROPERTIES OF STREPTOCOCCUS-GORDONII

Streptococcus gordonii gave rise to beta-haemolytic variants (Bhp(+) f or beta-haemolysin production) at frequencies of 10(-4)-10(-3) on agar medium containing washed horse erythrocytes. Bhp(+) variants reverted to the wild-type alpha-haemolytic phenotype (Bhp(-)) at the same freq uencies, There was a significant probability (greater than or equal to 0.1) that phase variation in Bhp and phase variation in the previousl y described Spp (sucrose promoted phenotype) would occur concomitantly , but there was no correlation between these phenotypes. There was evi dence also of independent phase variation in adhesion to saliva-coated hydroxyapatite (Asp for adhesion to salivary pellicles), in lactose-s ensitive coaggregation (Cls for coaggregation, lactose-sensitive) and in the concentrations of particular cell surface antigens (Cap for cel l antigen profile) in strains that had undergone phase changes in Spp and/or Bhp. Phase variation in all these phenotypes were transitions b etween high and low levels of activity and each appeared to occur as a n independent event. Significant associations (P much less than 0.0001 by contingency table analysis) between particular phenotypes such as Bhp and Asp and between Asp, Cls and Cap phenotypes, however, were app arent, The results suggest that S. gordonii cells become predisposed t o phase variation and that the resulting independent phenotypic change s may give rise to phenotypically diverse streptococcal populations ab le to accommodate rapid and transient environmental changes in the mou th.