Viability of Clostridial Spores and the Requirements of Damaged Organisms

Abstract

Summary. A method for counting viable anaerobic spores by roll tubes incubated in an atmosphere of hydrogen compared favourably with other techniques. Reproduction of environmental conditions in individual anaerobic jars did not significantly contribute to the overall error (Coefficient of Variation of viable count, 6·7%). Colony counts did not show a Poissonian distribution, and the significance of this is discussed. Optima for some conditions for counting 4 species of Clostridium and for suspensions of spores of Cl. welchii damaged by heat, γ‐rays or ethylene oxide have been established. Damaged spores were more exacting in their cultural requirements than were control organisms, and considerable variation in incubation temperature optima was found according to the sublethal treatment employed.