82 



PHYSIOLOGY OF THE FUNGI 



Recently, a cobalt-containing vitamin (B12) was isolated. This vitamin 

 is synthesized by Streptomyces griseus (Rickes et al., 1948) and some 

 bacteria. Whether S. griseus requires cobalt as an essential element for 

 growth or reproduction is not known. The synthesis of this vitamin is 

 necessarily dependent upon a supply of cobalt. Some bacteria are known 

 to be deficient for vitamin B12. 



PERIODICITY OF BIOLOGICALLY ESSENTIAL ELEMENTS 



Steinberg (1938a), Frey-Wyssling (1935), and others have considered 

 the problem of biologically essential elements in relation to the structure 



Table 15. A Portion of the Periodic Table of Elements Based on Atomic 



Number 

 The biologically essential elements are set in italics. Those elements essential for 

 fungi are marked with an asterisk. 



and atomic number of the elements. The biologically essential elements 

 are in italics in Table 15. It is noteworthy that the essential elements 

 tend to occur in groups with consecutive atomic numbers. Atomic num- 

 ber is a fundamental property of atoms and denotes the number of excess 

 positive charges on the nucleus. Only those elements which have certain 

 configurations are required by organisms. Why some organisms require 

 certain elements not required by others is not known. 



