THE MINERAL REQUIREMENTS FOR SPORULATION 7 



the very small amount of manganese that must be added to nutrient broth 

 to obtain spore formation: one part in twenty million. It can certainly be 

 stated without exaggeration that if such a small quantity of available man- 

 ganese had been naturally contained in nutrient and other complex broths, 

 the literature on sporulation research during the first half of this century 

 would be considerably different. 



The discovery of the manganese requirement for sporulation of aerobic 

 bacilli is a good example of a contribution made by applied research to 

 basic microbiology. As you may recall, Dr. Charney and his associates in 

 1951 were engaged in an antibiotic screening program and by chance dis- 

 covered that mycelia of a Streptomyces culture stimulate growth and spor- 

 ulation of bacilli on trypticase soy agar. Their curiosity was aroused by this 

 observation; they proceeded to find that the active principle in the mycel- 

 ium is manganese and that in trypticase soy and synthetic broths sporula- 

 tion but not growth is dependent on an external supply of this inorganic 

 ion. In the complex solid medium it is likely that constituents of the agar 

 bind the low concentration of native manganese so that only a suboptimal 

 quantity is available for growth. 



Further studies of the mineral requirements for sporulation can con- 

 tribute information that could be of immediate use in applied work. Such 

 studies might include the development of effective methods of binding or of 

 releasing essential minerals in the environment, which would result in either 

 suppression or stimulation of sporulation. Another example of an applied 

 use of inorganic nutrilite research is in analytical microbiology: at least 

 two useful methods of assay of manganese based on Charney's discovery 

 have already been published. 



Future work in this general area of basic sporulation research should 

 certainly include studies on the functions of the essential minerals. Dr. Cur- 

 ran has pointed out two types of possible functions: a structural function 

 as demonstrated by the moderate calcium requirement and a catalytic func- 

 tion as demonstrated perhaps by the small manganese requirement. We are 

 all familiar with the fact that some metals can substitute for others in the 

 activation of enzyme systems; and apparently magnesium, cobalt, or nickel 

 can, in a few cases, substitute for manganese. It would be of interest to 

 learn if such alkaline earth metals as strontium and barium can substitute 

 for calcium in its structural function. 



With respect to the catalytic function of manganese, the remote possibility 

 that the metal is involved in suppressing spore-inhibiting substances should 

 be kept in mind. Such inhibiting substances could be other metals that 

 might be antagonized by manganese or they could be organic molecules 

 that might be dissimilated by enzymes that require manganese. 



