COMPARISON OF EXTRACELLULAR PROTEASES PRODUCED BY AEROMONAS-SALMONICIDA STRAINS, ISOLATED FROM VARIOUS FISH SPECIES

Extracellular products (ECPs) of five typical and 25 atypical Aeromona s salmonicida isolates from various fish species and geographical loca tions were analysed by substrate specificity, inhibition of proteolyti c activity and substrate SDS-PAGE. The type strains of Aer. salmonicid a subsp. salmonicida and Aer. salmonicida subsp. achromogenes were inc luded for comparison. The results indicated that the strains formed si x protease groups. The proteases produced by the two type strains were of a different nature. All the typical strains belonged to one group and showed proteolytic activities comparable to P1 and P2 proteases. T hree atypical (oxidase-negative) strains secreted a protease comparabl e to P1. With the exception of these three, all strains produced metal lo-gelatinases. A metallo-caseinase (AsaP1) was detected in the ECP of subsp, achromogenes type strain and 10 of the atypical strains. A num ber of proteolytic components with different apparent molecular weight s (AMWs) were identified. These include caseinases with AMWs of > 100, 80, 60 and 30 kDa and gelatinolytic components with different AMWs, i ncluding some with AMW higher than P1 and lower than P2. The protease production of the isolates was not found to be host specific.