The occurrence of a 70‐kDa serine protease gene in typical and atypical strains of Aeromonas salmonicida

Abstract
The typical strains of Aeromonas salmonicida examined secreted a PMSF‐sensitive proteolytic activity, and with few exceptions, gave a positive colony hybridization with a 70‐kDa scrinc protease gene probe. By contrast, atypical strains produced a spectrum of responses with various combinations of (1) secreted/did not secrete PMSF‐inhibited protease, (2) colonies hybridized/did not hybridize with the gene probe, and (3) produced protease not inhibited by PMSF. It is suggested that certain strains might be reassigned as typical or atypical on the basis of the presence or absence of the protease gene.