4 HAROLD R. CURRA.N 



Apart from their utility in regulation of pH, bicarbonates may promote 

 the formation of spores by increasing COo concentration, as shown by 

 Powell and Hunter (1955). 



Proliferating vegetative cells, when centrifuged, washed, and shaken in 

 distilled water, form spores only if the prior growth medium is conducive 

 to sporulation. However, B. subtilis derived from an asporogenous medium 

 sporulates in distilled water when supplied with both yeast extract and salts, 

 but not if one of these supplements is omitted (Murrell, 1955), indicating 

 that the spore-generating mechanism is not seriously impaired by limited 

 cultivation in asporogenous media. 



The known facts, briefly surveyed, indicate that mineral salts are essen- 

 tial for the formation of bacterial spores. The fact that synthetic media with- 

 out added salts do not produce spores, and the fact that the inadequacy 

 for spore formation of many complex organic media can be corrected by the 

 addition of suitable minerals support this contention. The level of minerals 

 required for sporulation varies with the organism and with cultural condi- 

 tions such as kind and concentration of nutrients, oxygen supply, temper- 

 ature, and pH. The importance of manganese in the sporulating process is 

 conspicuously evident. It is required by a wide variety of mesophilic and 

 thermophilic aerobes, at concentrations above those needed for active vege- 

 tative growth, and, with one apparent exception, cannot be replaced by any 

 other mineral element. Manganese has been found to broaden the tempera- 

 ture and pH range over which sporulation occurs (Amaha et al, 1956). 



The specific function of the minerals in the spore-forming process is un- 

 known. It may be presumed that they exercise a catalytic role in the activa- 

 tion of many enzyme systems. They may thus expedite the complex enzy- 

 matic processes involving intracellular protein degradation and resynthesis 

 postulated by Hardwick and Foster as the basic mechanism in sporogenesis. 

 There is evidence that organic or inorganic phosphorus may supply some 

 of the energy used for the synthesis of spore constituents. The presence of 

 calcium above certain minimum levels seems to be a factor in the produc- 

 tion of thermostable spores; it may well be that calcium contributes to the 

 stability of spores by forming internal bonds with the low molecular weight 

 peptides which comprise much of the spore substance. 



References 



Amaha, M. Z., J. Ordal, and A. Touba. 1956. Sporulation requirements of 

 Bacillus coagulans var. thermoacidurans in complex media. J. Bact. 72: 

 34-41. 



Behring, E. 1889. Beitriige zur Aetiologie des Milzbrandes. Z. Hyg. Infek- 

 tionskrankh. 6: 117-144. 



Brewer, C. R., W. G. McCullough, R. C. Mills, W. G. Roessler, E. J. Herbst, 



