Study of the gelatinolytic activities of Escherichia coli cells before and after starvation in seawater by substrate gel electrophoresis

Abstract

Previous work has shown that clinical Escherichia coli strains, starved in seawater, are able to present residual growth, with subsequent alterations to their enzymatic activities and metabolism. Gelatinolytic activity of starved cells is of importance because it appears and increases gradually with time. In this work, several forms of gelatinolytic activity were detected by SDS-polyacrylamide gel electrophoresis, differing in molecular masses and appearance, before and after starvation of E. coli cells. The enzymic forms are classified into 4 categories according to the effect of certain inhibitors on the appearance of gelatinolytic activity: a. those whose appearance is inhibited by the chelating factors EDTA, 1, 10-phenanthroline and whose presence is also inhibited by N-ethylmaleimide (metalloproteinases with thiol group active); b. those affected by the presence of chelators, N-ethylmaleimide and Ca 2+ (Ca 2+-dependent metalloproteinases with thiol group active); c. those inhibited by chelators and activated in the presence of Ca 2+ (Ca 2+-dependent metalloproteinases) and d. those whose appearance is independent of the presence of inhibitors used. The forms of gelatinolytic activity of the fourth category coincide with enzyme forms that can also use cascin as substrate in electrophoresis. These data suggest that there are considerable differences in the gelatinolytic pattern of clinical strains of E. coli cells before and after starvation in seawater.