NUTRITION AND METABOLISM OF MARINE BACTERIA XII

Abstract

Drapeau, Gabriel R., (Macdonald College of McGill University, Quebec, Canada) and Robert A. MacLeod . Nutrition and metabolism of marine bacteria. XII. Ion activation of adenosine triphosphatase in membranes of marine bacterial cells. J. Bacteriol. 85: 1413–1419. 1963.—Isolated membranes of two species of marine bacteria, a Pseudomonas and a Cytophaga , have been shown to possess adenosine triphosphatase activity. The optimal pH for enzyme action of both organisms was 8.8. The enzyme system was found to be capable of splitting inorganic o -phosphate from adenosine triphosphate (ATP), adenosine diphosphate, adenosine monophosphate, and inosine triphosphate but not from inorganic pyrophosphate. Mg ++ was required for enzyme activity; with the Pseudomonas species, the optimal Mg ++ to ATP ratio was 1:1. Ca ++ could not replace Mg ++ . In the presence of the optimal concentration of Mg ++ , the enzyme system was further stimulated, nonspecifically, by a number of different salts. Maximal activation was achieved at an ionic strength of 0.3 to 0.4. No evidence of an adenosine triphosphatase specifically activated by a combination of Na + and K + was obtained with either organism. No effect of ouabain on either the membrane adenosine triphosphatase activity or Na + transport by whole cells could be detected. The results suggest that the mechanism of ion regulation in marine bacterial cells is different from that in animal cells.