BIOGRAPHICAL MEMORANDA 



priate experiments led to the conclusion that the conversion of carbon 

 monoxide by these organisms, Methanosarcina barken and Methano- 

 bacterium formicicum, proceeds in two stages, viz-, an initial conversion 

 of carbon monoxide and water to carbon dioxide and hydrogen, fol- 

 lowed by a reduction of carbon dioxide with the hydrogen liberated 

 in the first reaction; the fermentation can thus be expressed by the 

 equations: 4 CO + 4 H 2 ^ 4 C0 2+4 H 2 



C0 2 + 4 H 2 -> CH 4 +2H 2 

 4 CO +2H 2 -> 3C0 2 + CH 4 



Ms. barkeri could accomplish this conversion in an atmosphere of pure 

 carbon monoxide ; Mb. formicicum appeared somewhat sensitive to this 

 gas, tolerating it in concentrations up to about 12 per cent. 



While investigating the methane fermentation in ethanol-calcium 

 carbonate media, Barker [1937a] had also observed the formation of 

 higher fatty acids, especially butyric and caproic acids, in those crude 

 cultures that contained, besides the methane producing organisms, 

 an anaerobic sporeforming bacterium. This organism was subsequent- 

 ly isolated in pure culture and described as Clostridium kluyveri ; this 

 became the starting point for the highly important studies of Barker 

 and Stadtman on the mechanism of fatty acid synthesis. 



In the meantime it had also become apparent from studies in other 

 laboratories that carbon dioxide could no longer be considered as a 

 mere end product of the metabolic activities of non-photosynthetic or- 

 ganisms acting on organic substrates. For simultaneously with the 

 demonstration that the methane fermentation represents a process of 

 carbon dioxide reduction, three other metabolic reactions had become 

 known that involve carbon dioxide as one of the participating molec- 

 ular species. These were : 

 /. The synthesis of formic acid from carbon dioxide and hydrogen 



under the influence of B. coli, which Woods had shown to catalyze 



the reversible reaction, 



HCOOH^C0 2 +H 2 



This must have come as a severe shock to Kluyver who, some ten 

 years earlier, had strenuously maintained that such a formation of 

 formic acid, postulated by De Graaff, was too improbable to be 

 taken seriously. 



118 



