ORGANIC ACIDS 81 



essential ions in solution or limit growth by removing ions (183); 

 which of these two opposite effects will occur is determined by the 

 solubilities of the chelate complexes and the metallic salts at the cul- 

 ture pH chosen. 



The non-fatty organic acids which are most often utilized by fungi 

 are those, e.g., citrate, succinate, and malate, which are products of 

 glucose metabolism. Most of the data are from studies on common 

 saprophytes and it appears that utilization is highly specific. Thus 

 Penicillium janczewskii grows well on succinate (23); succinate is a 

 relatively poor carbon source for P. javanicum (121) and is not utilized 

 at all by P. digitatum (65). Because of the likelihood that cells may be 

 impermeable to acids, especially hydroxy acids, nutritional data have 

 no necessary relevance to the acid metabolism of the cell. 



Tartaric acid, the utilization of which by a fungus is so important in 

 the history of both crystallography and microbiology (148), is in gen- 

 eral not a good carbon source for fungi, although it is utilized as well 

 as glucose by Memnoniella echinata (150). The growth of some com- 

 mon fungi with tartrate has been surveyed by Stadtman et al. (190); 

 an adaptive tartrate-decomposing system of Aspergillus versicolor has 

 been described (10). The dextrorotatory isomer is used preferentially 

 (70). 



Oxalic acid is used by few microorganisms, among which are Pro- 

 actinomyces sp. and a strain of Aspergillus oryzae (137), Psalliota 

 bispora (216), and a few bacteria (104). Possibly, the insolubility of 

 calcium and magnesium oxalates results in a removal of these ions 

 from solution and a consequent limitation of growth in oxalic acid 

 media. 



Malonic acid is used, although it is not a favorable carbon source, 

 by a few fungi and actinomycetes (23, 92, 99). 



Inclusive studies of polyfunctional organic acids in nutrition have 

 been reported by Camp (30), Tamiya (201), and Steinberg (195). 



The lower fatty acids — formic, acetic, propionic, etc. — are as a rule 

 poorly utilizable or even toxic. Propionic acid, in fact, is employed as 

 a fungistatic agent. Some fungi, however, do make at least some 

 growth with these acids, particularly with acetate; on a carbon basis 

 acetate is equivalent to glucose for Allomyces javanicus (124). Quali- 

 tative data (175) indicate that Leptomitus lacteus can grow with any 

 of the lower organic acids, including some that are almost uniformly 

 toxic to the higher fungi. Probably, it will be found that the lower 

 fungi utilize fatty acids better than the more extensively investigated 

 higher forms. The utilization of acetate by Penicillium chrysogenum 

 is strongly pH dependent (95). 



