BIOCHEMICAL CHANGES OCCURRING DURING SPORULATION OF BACILLUS CEREUS T. II. EFFECT OF ESTERS OF ORGANIC ACIDS ON SPORULATION

Gollakota, K. G. (University of Illinois, Urbana) and H. Orin Halvorson. Biochemical changes occurring during sporulation of Bacillus cereus T. II. Effect of esters of organic acids on sporulation. J. Bacteriol. 85:1386-1393. 1963.-Sporulation of Bacillus cereus T in yeast extract-glucose-minerals medium was specifically inhibited by alpha-picolinic acid (APA), if the acid was added before the pH of the culture began to rise. The effects of APA could be reversed by aspartic acid or asparagine, among the amino acids, and by intermediates of the tricarboxylic acid cycle, with the exception of alpha-ketoglutarate and fumarate. Formate, malonate, and certain other organic acids also possessed this ability. Succinate was the best reversing agent. Fluoroacetic acid (FAA) also inhibited sporulation, but had no effect on vegetative growth or germination of spores of B. cereus T. Unlike APA, FAA inhibited sporulation even when added after the pH of the culture had started to rise. Bisulfite was similar to FAA in its effects on sporulation. With the exception of pyruvate, acetate, aspartate, and malate, most of the compounds reversing the effects of APA also overcame the effects of FAA or bisulfite on sporulation. Esters of some of the acids reversing the effects of the above inhibitors were studied for their action on germination, growth, and sporulation. Ethyl pyruvate prevented germination of the spores, slowed down growth, and inhibited sporulation. Ethyl malonate and ethyl succinate inhibited only sporulation. All the above inhibitors prevented the synthesis of dipicolinic acid (DPA) also. When B. cereus T was grown in the absence of glucose (in extracted yeast extract-minerals medium), the above inhibitors had no effect on sporulation. Ethyl oxamate permitted sporulation, but the spores produced were heat-sensitive. Ethyl pimelate caused lysis when added before the pH of the culture began to rise. When added after the pH of the culture began to rise, it also permitted sporulation, and the spores were sensitive to heat. (These heat-sensitive spores were refractile and dormant, and did not stain with crystal violet. However, they germinated normally, losing refractibility and became stainable.) The effect of ethyl oxamate and ethyl pimelate could be overcome by DPA. APA, FAA, ethyl malonate, and ethyl succinate also inhibit the sporulation of a number of other bacilli.