THE BACTERIAL ENDOSPORE 33 



mental factors upon germination. It is necessary, at this point, 

 to indicate that germination is used here in a somewhat different 

 sense than it has commonly been employed in the past. In older 

 literature the word has been used to describe all of the changes 

 taking place during the development from spore to fully grown 

 vegetative cell. The changes observed by Hills and later by 

 Powell and other workers occur very early in the process, and 

 bacteriologists have come to use the term to encompass these 

 early changes only, and to use the word outgrowth to represent 

 all the other changes. 



A number of investigators have shown that many species of 

 spores require a heat shock as a sensitizing mechanism before 

 they will respond to germination nutrients. The length of the 

 time of heating and the temperature required vary with different 

 species, the age of the spores, and the conditions of storage. 

 Freshly grown spores of Bacillus cereus can be adequately 

 sensitized by heating to 65' for about 15 min. On the other hand, 

 spores of Bacillus stearothermophilus have to be heated to 100° 

 or more for an equivalent length of time". Most workers in the 

 field believe that this heat sensitization initiates biochemical 

 reactions that either release compounds to stimulate germina- 

 tion or alter the permeability of the spore wall. In any event, 

 precise information as to what actually does happen is not 

 available. 



The rate of germination is notably influenced by the tempera- 

 ture. Most of the investigators have been observing germination 

 at room temperature, and it has been their common observation 

 that it will not take place in a refrigerator or at a lower tempera- 

 ture, nor will it occur at 60''^. On the other hand, Wynne^ 

 claimed that spores from some species of anaerobes germinated 

 at 75° when they were suspended in a solution containing 

 glucose that had been autoclaved in an alkaline medium. 

 Recently, Foster^ reported that Bacillus megatherium spores 

 will germinate at temperatures between 70' and 100 . In our 

 own laboratories, we find spores of B. cereus will germinate 

 rapidly in the presence of L-alanine and adenosine at room 



References p. 59 



