16 NUTRITION OF FUNGI 



and Waksman and Foster (1939) with gluconic acid production 

 by Rhizopus. 



Other elements as nutrients. A lame number of other ele- 

 ments have been tested to determine whether they are essential 

 for the metabolic activities of fungi. The role of boron for 

 Penicillhnn glaucum and Aspergillus niger was investigated by 

 Boeseken and Watermann (1912). Molybdenum and gallium 

 have been found to be essential for A. niger by Steinberg (1936, 

 1937, 1938), and the same investigator (1920) determined that 

 uranium and cobalt can partly replace iron and zinc for this spe- 

 cies. Lockwood et al. (1934) found that columbium, chromium, 

 molybdenum, and tungsten are favorable for the production of 

 fats by Penicillium javanicum. Steinberg (1938) tested 76 chemi- 

 cal elements with the result that iron, zinc, copper, manganese, 

 gallium, and molybdenum comprise all that may be regarded as 

 essential for A. niger. Other extended systematic studies, espe- 

 cially those of Pirschle (1934, 1935), involve the effects upon 

 growth of many elements. Javillier (1913) concluded that co- 

 lumbium and beryllium cannot replace zinc, which, when present 

 in concentrations of 1 to 2 ppm, increased the amount of growth 

 of A. niger 58 times. 



ORGANIC NUTRIENTS OF FUNGI 



Those investigators who laid the foundations for an understand- 

 ing of the mineral requirements of fungi also contributed to the 

 establishment of bases for comprehending the organic compounds 

 utilized in the growth of these organisms. They noted that fungi 

 vary in response to the addition of different carbon compounds 

 employed to fortify synthetic media. They arrived at this con- 

 elusion by what is commonly designated the "trial and error 

 method." Apparently Pfeffer (1895) was the first to study this 

 problem with the planned purpose of determining the quantitative 

 acceptability to a particular fungus of various organic substances. 

 In nearly all subsequent studies either of two purposes has been 

 maintained: (1) to find whether the given fungus would grow 

 upon the proffered carbon compound, in order to determine its 

 enzyme-producing ability, or (2) to measure the comparative rate 

 of growth of the fungus on different substrata, using the weight 

 of the mycelial mat or the increase in diameter of colonies as a 



