ENERGY TRANSFORMATION 407 



able to develop heterotrophically. The methane cannot be replaced 

 by hydrogen or carbon monoxide, but can be replaced by various 

 organic compounds, such as alcohols, carbohydrates, and salts of 

 organic acids. 



The utilization of carbon monoxide as a source of energy by bacteria 

 was demonstrated by Kaserer: 



CO + K0 2 ) = C0 2 + 74 Cal. 



Closely related processes to the autotrophic utilization of inorganic 

 compounds are the oxidation of simple organic compounds, of which 

 we need mention only the oxidation of alcohol to acetic acid, and the 

 utilization of hydrocarbons as sources of energy. The CO2 assimila- 

 tion of these as well as of the methane bacteria is not established. The 

 physiology of these organisms is little understood. 



The acetic acid bacteria are divided, 44 on the basis of their carbon 

 and nitrogen utilization, into two groups: (1) haplotrophic, those which 

 obtain their energy from the oxidation of alcohol, and (2) symplo- 

 trophic, or those which require organic compounds. The energy utili- 

 zation of the former is of interest here: 



CH 3 -CH 2 -OH + 2 = CH3COOH -f H 2 + 112 Cal. 



1.47 Cal. are thus liberated for every gram of alcohol oxidized. These 

 bacteria do not need any other organic matter, either as sources of 

 energy or carbon. The tendency was, therefore, to classify these 

 organisms with the autotrophic bacteria. According to Neuberg, 45 

 however, in the case of the acetic acid bacteria the ethyl alcohol is first 

 oxidized to acetaldehyde; this is either further oxidized to acetic acid 

 or is used for the synthesis of the microbial protoplasm. These or- 

 ganisms, therefore, are not autotrophic since they do not derive their 

 carbon from carbon dioxide and, in regard to energy and carbon utili- 

 zation, may both be classified with the heterotrophic organisms. 



CH 3 ■ CH 2 • OH CH 3 • CH 2 OH 



CH 3 • CH, • OH -> CH 3 • CHO CH 3 • CHO 



\ \ 



CH 3 • COOH CH 3 • COOH 



44 Janke, A. Forschungsergebnisse auf dem Gebiete der Essigbakteriologie 

 und Fortschritt der Garungsessigindustrie. Centrbl. Bakt. II, 53: 81-124. 1921. 



46 Neuberg, C, and Windisch, F. Vom Wesen der Essiggrirung und von 

 verwandten Erscheinungen. Die Naturwiss., 13: 993-996. 1925; Biochem. 

 Ztschr., 166: 454-481. 1925.< 



