414 PRINCIPLES OF SOIL MICROBIOLOGY 



organisms, if conditions are made favorable, as by the addition of free 

 oxygen. 



2 CH 3 • CHOH • COOH + 2 2 = 2 CH 3 COOH + 2 C0 2 + 2 H 2 + 240 Cal. 

 Lactic acid acetic acid 



2 CH 3 COOH + 3 2 = 2 HCOOH + 2 C0 2 + 2 H 2 + 294 Cal. 

 Formic acid 



2 HCOOH + 2 = 2 C0 2 + 2 H 2 + 126 Cal. 



The more recent conceptions of oxidation-reduction processes (p. 520), 

 tend to explain the mechanism of energy utilization under "anaerobic" 

 conditions. Quastel and associates 59 have shown that anaerobic growth 

 of an organism can be expected to take place when a pair of organic 

 compounds, neither of which supports anaerobic growth, fulfill the 

 following conditions: (1) both are "activated" by the organism so that 

 simultaneous oxidation and reduction may occur; (2) energy necessary 

 for growth is liberated in the interaction; (3) as a result of such an in- 

 teraction some substance is produced which is capable of entering into 

 the synthetic processes of the cell. These conditions are fulfilled for 

 Bad. coli by lactic acid or glycerol, on the one hand, and nitrate or 

 fumerate, on the other, the former contributing hydrogen and the 

 latter utilizing it. 



CH 2 OH-CH OH-CH 2 OH + COOH -CH:CH- COOH = CH 3 CH OH -COOH + 



COOH • CH 2 • CH 2 • COOH + 33 Cal. 

 glycerol Fumaric acid 



CH 2 OH • CH 2 OH + 2COOH • CH:CH • COOH = CH 3 • CO COOH + 



2COOH • CH 2 • CH 2 • COOH + 50 Cal. 



Malic and aspartic acids can also serve as weak hydrogen acceptors 

 for Bad. coli. In some cases, the same substance can serve both as 

 the hydrogen donator and acceptor, as brought out by the Cannizzaro 

 reaction, especially in the case of pyruvic acid: 



CH 3 • CO • COOH + H 2 + CH 3 • CO • COOH = 

 pyruvic acid pyruvic acid 



CH 3 • CHOH • COOH + CH 3 • COOH + C0 2 + 15 Cal. 

 lactic acid acetic acid 



69 Quastel, H., Stephenson, M., and Whetham, M. D. Some reactions of 

 resting bacteria in relation to anaerobic growth Biochem. Jour., 19: 304-317. 

 1925; Quastel, J. H., and Stephenson, M. Further observations on the anaerobic 

 growth of bacteria. Ibid., 660-666. 



