Electrophoretic analysis of ureases in Streptococcus salivarius and in saliva

Experimental conditions were established for the extraction, electrophoresis and detection of urease isoenzymes from Streptococcus salivarius. Thiol concentrations were critical and ureases from different strains varied in ease of dissociation. A characteristic pattern was obtained for 30 ureolytic S. salivarius strains isolated from; saliva (6), dental plaque (12), artificial dental plaque (6) and non-oral sources (6), and also for a ureolytic Streptococcus bovis from artificial plaque. One non-oral S. salivarius strain had ureases with slightly slower mobility. The electrophoretic pattern and mobility of ureases extracted from human mixed salivary bacteria were identical to those from S. salivarius except for an additional set of urease bands from unknown species of bacteria. There were no ureases from saliva matching those from Staphylococcus epidermidis--a contributor to ureolysis in artificial plaque. We conclude that there is considerable biochemical homogeneity among S. salivarius ureases and possibly other ureolytic streptococci. In saliva, urea is metabolized mainly by streptococcal ureases.