The Problem of “Dormancy” in Bacterial Spores

Our experience with the germination of spores of various species of clostridia, especially Clostridium botutinum, has led to conclusions that we believe warrant the consideration of investigators of this group of organisms and of the aerobic sporeformers as well. Pertinent observations have been made by previous authors, but it appears that all the recent available evidence on, and various aspects of, the dormancy problem have not hitherto been crystallized into one comprehensive concept. The essential points already established (Morrison and Rettger, 1930a,b, for review of previous literature; Curran and Evans, 1937; Olsen and Scott, 1946; Wynne and Foster, 1948a; -Foster and Wynne, 1948) are these: (1) Colony counts from a spore suspension may be submaximum in a few days' incubation, and increase with time over prolonged periods. This indicates delayed germination and is a well-known phenomenon for both aerobic and anaerobic spores. This is the characteristic feature of classical dormancy. (2) The effect depends on the medium used, being marked in some and nonexistent in others. (3) The final spore counts of a given suspension depend greatly upon the medium employed, though in each medium counts are at the maximum obtainable in it. (4) Certain substances, notably soluble starch (0.1 per cent), eliminate the delayed germination in some media. In others the starch increases the final maximum count, whereas in strn others it has no apparent effect. In general, all complex media preferred for counting spores show the starch effect. Data exemplifying all these points may be found in table 1. From the information in the literature, as well as in table 1, the following points may be made: (a) The so-called "dormancy" in these organisms is not an inherent function of the spores, but rather of the medium in which the spores are placed to germinate. (b) Even when "dormancy" occurred, or in media with low final counts, the large size of colonies speaks against a nutritional inadequacy.