THE GERMINABILITY OF SPORES OF A PSYCHROTOLERANT, NONPROTEOLYTIC STRAIN OF CLOSTRIDIUM-BOTULINUM IS INFLUENCED BY THEIR FORMATION AND STORAGE-TEMPERATURE

The formation and storage temperatures of Clostridium botulinum spores are shown to influence their subsequent ability to germinate. Spores were formed at 10 degrees, 20 degrees, 30 degrees and 37 degrees C and following harvest were stared as aqueous suspensions at 20 degrees C (ambient temperature), 4 degrees C (refrigerated) or -20 degrees C (fr ozen) for periods of up to 1 month. The spores formed at 20 degrees C germinated most rapidly and to the greatest extent. When the spores we re germinated immediately after harvest (fresh), there was no differen ce in the germinability of those spores formed at 20 degrees or 30 deg rees C, whether or not they had been heat-shocked before use. However, following storage overnight or longer, differences in the relative ge rminabilities of the different spore samples were seen. Spores which h ad been stored at ambient temperature overnight germinated significant ly faster and to a greater extent than did those which had been stored for up to 1 month. Similar differences were also observed between spo res germinated fresh and those stored overnight, when the spores were stored refrigerated or frozen. Germinability tvas also influenced by t he temperature of storage, since there were differences between spores formed at the same temperature but stored at different temperatures f or the same period of time: for example, when spores which had been fo rmed at 20 degrees C were germinated at 10 degrees C following a heat- shock, those which had been stored at ambient temperature germinated f aster and to a greater extent than did those which had been stored ref rigerated or frozen. It is concluded that there is a complex interacti on between formation, storage and germination temperatures, which dete rmines spore germinability. The fact that the changes are time-depende nt and can occur in the frozen state is taken to mean that they are ph ysico-chemical rather than metabolic. It is also significant in relati on to refrigerated foods which are at risk from Cl. botulinum in that changes which occur during cool or frozen storage can enhance the germ inability of spores if the temperature rises above that of chill cabin ets.