Isolation and Partial Characterization of Extracellular Proteases Produced by Isolates of Flavobacterium columnare Derived from Channel Catfish |
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| Abstract: | Abstract Proteases of 23 isolates of Flavobacterium columnare derived primarily from channel catfish Ictalurus punctatus raised in the southeastern United States were isolated and partially characterized. The bacterial isolates were divided into two groups according to the apparent molecular masses of proteases after zymographic resolution by nonreducing, nondenaturing sodium dodccyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) with gelatin as the protease substrate. The 15 isolates in group 1 had two proteases with apparent molecular masses of 58 and 53.5 kilodaltons (kDa). Eight group-2 isolates produced three proteases with apparent molecular masses of 59.5, 48, and 44.5 kDa. Culture medium had an effect on the amount of protease produced by F. columnare LA 88–173. More protease was produced in a medium with low nutrients and salt (Ordal's medium) than in media with higher concentrations of nutrients or salts (TYES, Hsu-Shotts, modified Shieh's media). No differences were observed in the apparent molecular masses of the two proteases of F. columnare LA 88–173 produced in the various media or with different incubation times. Two proteases with apparent molecular masses of 58 and 53.5 kDa were seen as early as I d after inoculation, and these molecular masses did not change during the 7-d experiment. A sharp increase in protease production occurred during the first 24 h of incubation with minimal increase during the remaining 7 d of the experiment. All 23 isolates of F. columnare degraded the gelatin and casein incorporated into TYES agar medium but only 7 of the 23 isolates degraded elastin. |
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