64 CLARENCE F. SCHMIDT 



to the conclusion that we are gathering data which, up to the present time at 

 least, do not lend themselvs to many overall generalizations. There are, 

 however, certain factors which seem to be necessary in the majority of cases, 

 in order for germination to proceed rapidly and completely. The most obvi- 

 ous of these factors are heat activation, the presence of L-alanine, and a 

 riboside. 



The heat activation of spores prior to incubation with various chemical 

 stimulants often results in a more complete or more rapid germination. This 

 characteristic response seems to be more common among the aerobic spore 

 formers than among the anaerobes. Six out of nine species of aerobic spore 

 formers, for which optimal germination conditions have been recorded, have 

 been reported in at least one instance to require heat activation. Furthermore, 

 in some cases where heat activation was either not used or not required, the 

 spore suspensions tested had been pasteurized during their preparation. 

 Although Dr. Schmidt and several others have reported that the effect of 

 heat activation is lost rapidly, it may be possible that pasteurization of spores 

 of some species may produce a more permanent change which makes sub- 

 sequent heating unnecessary. In other cases where heat activation was not 

 used, the spore suspensions were cleaned of vegetative cells by exposure to 

 sonic oscillation ( Heiligman, Desrosier, and Broumand, 1956). The effect 

 of sonic oscillation on these spores has apparently not been reported, but in 

 view of the reports which were reviewed by Rahn (1945), that sonic oscilla- 

 tion is an effective lethal agent, it may be that mild sonic treatment sufficient 

 to destroy vegetative cells, but not spores, has an effect similar or even iden- 

 tical to that of mild heat treatments. 



The stimulatory action of mild heat on germination is apparently not a 

 permanent characteristic. Church and Halvorson (1956) reported that fresh 

 spores of Bacillus cereus var. terminalis, after heat activation, germinated 

 in the presence of L-alanine and adenosine. After 5 years of aging, however, 

 these spores germinated rapidly and completely without heating in the pres- 

 ence of either L-alanine or adenosine, or after heat activation alone. 



Heat activation, in addition to providing more rapid and complete germi- 

 nation, may also alter the germination requirements. Levinson and Sevag 

 (1953) found that spores of Bacillus megaterium germinated without heating 

 in a L-alanine-adenosine-glucose-glutamate-salts medium, but after heat activa- 

 tion only glucose and L-alanine were required. Powell and Hunter (1955) 

 reported that unheated spores of Bacillus subtilis required L-alanine. adeno- 

 sine, glucose, and tyrosine for optimum germination, while heated spores 

 required only glucose and adenosine. In addition to those cases reported in 

 the literature where heating is not beneficial, in our laboratory Amaha ( 1956) 

 found that unheated spores of B. coagulans germinated rapidly and completely 



