Diversity of extracellular proteases among Aeromonas determined by zymogram analysis.

AIMS

The current research was aimed at comparing extracellular proteolytic activities and zymogram profiles among Aeromonas spp.

METHODS AND RESULTS

Extracellular proteases of 47 strains of Aeromonas were analyzed by substrate (casein and gelatin) co-polymerized SDS-PAGE, and caseinolytic activity was determined using azocasein. Large variation on caseinolytic activity was evidenced. In general, the caseinolytic activity of Aeromonas hydrophila strains was significantly higher than that of other Aeromonas species. Several caseinolytic and gelatinolytic profiles were detected in Aeromonas. Cluster analysis allowed separating Aeromonas strains in four and three groups, based on their caseinolytic and gelatinolytic profiles, respectively. Although not specific patterns were evident, most Aer. hydrophila strains were clustered together and differed from Aeromonas caviae strains. The main caseinases of Aer. hydrophila were a serine protease with an apparent molecular weight (AMW) of 56 kDa and a metalloprotease with AMW of 22 kDa. Gelatinase profiles were characterized by the presence of high molecular weight metalloproteases (84 and 93 kDa), although the most active enzyme was a serine protease with AMW of 56 kDa. Other new caseinases and gelatinases were detected in specific Aeromonas strains.

CONCLUSIONS

Aeromonas strains exhibited several extracellular proteolytic profiles, with a larger inter than intraspecific variation. Moreover, zymogram analyses allowed identifying new caseinases and gelatinases in Aeromonas.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report on the intra- and interspecific variation of proteolytic profiles in Aeromonas determined by zymogram analysis, including the detection of new caseinases and gelatinases in this genus.