Costilow, Ralph N. (Michigan State University, East Lansing). Fermentative activities of control and radiation-"killed" spores of Clostridium botulinum. J. Bacteriol. 84:1268-1273. 1962.-Spores of Clostridium botulinum 62-A exposed to high levels of ionizing radiation will undergo the initial steps in germination as rapidly as control spores. Manometric experiments demonstrated that these irradiated nonviable spores would ferment a tryptic digest of casein (Trypticase) at an increasing rate during germination, with the production of CO(2) and H(2). There was, however, an increasing lag in the development of rapid rates of fermentation as the radiation level was increased. Such a lag could be simulated by the addition of chloramphenicol, and the two effects were additive. By using high spore concentrations (about 8 mg/ml), it was possible to detect the fermentation of a number of individual amino acids and of glucose. Irradiation of spores at 8.3 x 10(5) rads had no measurable effect on the fermentation of l-arginine or glucose, or on the endogenous rate, but it partially inhibited the Stickland reaction with l-alanine and l-proline as substrates. The endogenous activity and the l-alanine, l-proline fermentation were also inhibited by chloramphenicol to basic levels which were the same in both control and irradiated spores. Neither the l-arginine nor glucose fermentation was inhibited by this antibiotic. The data indicate that spores of C. botulinum 62-A contain basic levels of the enzymes required for their primary catabolic processes, and that, as expected, ionizing radiation levels sufficient to render the spores nonviable do not significantly affect these enzymes. Furthermore, it is indicated that spores exposed to radiation levels of up to 1.25 x 10(6) rads retain the ability to synthesize new protein, although it appears to be somewhat impaired.