NUTRITIONAL AND ENVIRONMENTAL CONDITIONS 



19 



= NO MnSO, 

 Q — D = 1 ppm MnSO, 



O O = 10 ppm MnSOi 



100 ppm MnSO 



distinguished between conditions which favor vegetative growth and con- 

 ditions which specifically favor sporulation. The technique of replacement 

 cultures, i.e., the procedure of producing the vegetative cells in a medium 

 favorable for growth and then suspending these cells in distilled water or 

 in a second modified medium for sporulation, provides a means of parti- 

 ally separating growth from sporulation. Using this technique, Foster and 

 his colleagues, Grelet (1951, 1955), Tinelli (1955), and others have col- 

 lected data which have been helpful to our understanding of this phe- 

 nomenon. 



Environmental factors affecting sporulation 



/. Physical factors 



(a) Temperature. There seems to be a general agreement that the opti- 

 mum temperature for sporulation is close to that for growth, but the range 

 is narrower. 



(b) pH. Likewise the optimum pH for sporulation is similar to that for 

 growth^ but the range is narrower. Some of our own data substantiate this, 

 as shown in Figs. 1 and 2. Bacillus coagulans [NCA strain 43P] was cul- 

 tured on an agar slant medium, which, except for the agar, was chemically 



