154 PROVISION OF energy: oxidation 



record the cycle as known in other tissues and to point out that, 

 although there is evidence accumulating that some such 

 system does exist in bacteria, its nature and occurrence in any 

 bacterium has yet to be proved. 



The oxidation process makes ATP available and this, in 

 turn, makes energy available for synthetic purposes. If we 

 follow the oxygen uptake during the oxidation of acetate by 

 Esch. coli, we find that the amount of gas taken up corresponds 

 to 60-75 per cent, of that required by the above equation for 

 complete oxidation. If the residual substrate is estimated, 

 we find that all the acetic acid has disappeared, although the 

 oxygen consumption does not correspond to 100 per cent, 

 oxidation. The portion of the acetic acid which has not been 

 oxidised is assimilated and incorporated in the cells by what is 

 called a process of ''oxidative assimilation." If we assume 

 that the material assimilated by the cells is of the nature 

 (HCOH), then the true equation for the oxidation is : 



2CH3.COOH + 3O2 > (HCOH) + 3CO2 + 3H2O. 



If the oxidation is carried out in the presence of sodium azide 

 or dinitrophenol the oxidative assimilation is prevented and 

 the oxygen consumption then corresponds to quantitative 

 oxidation according to Equation 7. 



OXIDATION BY STRICT ANAEROBES 



The methane that arises from stagnant and putrescent pools 

 is produced by bacterial action. The organisms responsible 

 belong to the genus Methanobacter, and their activities have 

 been studied in detail by Barker and his colleagues. Methano- 

 bacter omeliansJdi, like other organisms of this group, is a 

 strict anaerobe, and obtains energy by the oxidation of 

 alcohols. As it is a strict anaerobe it cannot utilise oxygen for 

 the oxidation process, but carries out an oxidation-reduction 

 process in which the H-acceptor is carbon dioxide, which is 

 reduced to methane according to the equation: 



2CH3.CH2OH + CO2 > 2CH3.COOH + CH4. 



