Detection of the extracellular proteases of Bacteroides nodosus in polyacrylamide gels: a rapid method of distinguishing virulent and benign ovine isolates.

The extracellular proteases of Bacteroides nodosus were separated electrophoretically on polyacrylamide slab gels at pH 8 . 8. Proteolytic activity was detected by placing the gel slab on a layer of gelatin-agar and allowing hydrolysis of the gelatin to occur. After two hours at 37 degrees C, the unhydrolysed gelatin was precipitated with mercuric chloride in acid. The proteolytic zymograms of 14 benign strains were identical. The zymograms of 10 virulent strains yielded two closely related sets of proteases. The reproducible difference observed between the respective zymograms readily provides a rapid diagnostic test to assist in the identification of benign and virulent strains of B nodosus.