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TEMPERATURE-SENSITIVE FORMIC HYDROGENLYASE IN A PSYCHROPHILIC BACTERIUM

Department of Bacteriology and Public Health, Washington State University, Pullman, Washington

ABSTRACT

UPADHYAY, J. (Washington State University, Pullman) AND J. L. STOKES. Temperature-sensitive formic hydrogenlyase in a psychrophilic bacterium. J. Bacteriol. 85:177–185. 1963.—A temperature-sensitive formic hydrogenlyase has been found in a psychrophilic bacterium, strain 82. The enzyme was most active at 30 C, but completely inactive at 45 C. In contrast, formic hydrogenlyase in mesophilic Escherichia coli was most active at 45 C, and completely inactivated only at 70 C. The hydrogenlyase-forming system in psychrophile strain 82 also was unusually heat-sensitive. It was inactivated at temperatures above 20 C; whereas, in mesophilic E. coli, Proteus vulgaris, and Salmonella oranienburg, hydrogenlyase was formed even at 45 C. This heat sensitivity of the enzyme-forming system accounted fully for the inability of strain 82 to produce gas from carbohydrates above 20 C. Psychrophile hydrogenlyase resembled the mesophilic variety in several respects. It was most active at pH 5.0. It was not formed by cells grown aerobically. It could be induced in resting-cell suspensions by use of glucose, formate, and casein hydrolysate as supplements, although several times as much glucose was required as for enzyme induction in strains of E. coli and Salmonella. The enzyme was formed best at pH 7.5, which was somewhat higher than the pH of 6 to 7 for mesophile hydrogenlyase, and by cells taken from the beginning of the stationary phase of growth.