Electrophoretic detection of proteases from different Flexibacter columnaris strains and assessment of their variability

Proteases with apparent molecular weights of 47, 40, 34 and 32 kD were identified in cell-free extracellular products (ECP) of Flexibacter columnaris by using substrate SDS-polyacrylamide gel electrophoresis. Similar protease profiles were associated with ECP collected at intervals during several days in culture. Furthermore, the proteases produced by a collection of 13 F. columnaris isolates from a variety of fish species and geographic sources showed great uniformity but differed markedly from the protease profiles of 7 other gliding bacteria examined. The 13 F. columnaris isolates degraded gelatin, casein, hemoglobin, fibrinogen and elastin. Results of experiments with protease inhibitors indicated that zinc metalloproteases constitute a major component of the extracellular proteases of F. columnaris .