72 PHYSIOLOGY OF BACTERIA 



B. In the oxidation of organic compounds 



Kg. calories 



Methane 3.20 



Acetic acid 3 . 272 



OxaHc acid 3 . 80 



Palmitic acid 3 . 259 



Dextrose 3.508 



Maltose 3.520 



Starch 3.530 



Asparagin 3.218 



Uric acid 3 . 198 



Legumin 3.291 



Elastin 3.240 



Fat (animal) 3.293 



Glycerine 3.5 



Alcohol 3.4 



acceptors if we consider only the energy viewpoint. 

 The best is doubtless hydrogen peroxide because energy 

 could be gained by reducing it, i.e. by adding hydrogen 

 to it. The other compounds offer a certain resistance to 

 reduction. The energy required to remove 1 gm. of 

 oxygen from these compounds is lowest in the nitrates. 

 Let us assume a bacterium under anaerobic conditions 

 in a medium containing oxalic acid and nitrate. Nitrate 

 could act as hydrogen acceptor, oxalic acid as hydrogen 

 donator. 



C2O4H2 -^ 2CO2 + 2H + 3.80 cal. per gram oxygen 



HNO3 +2H -^HN02 +H2O - 1.16 cal. per gram oxygen 



C2O4H2 + HNO3 -^ 2CO2 + H2O + HNO2 + 2.64 cal. per gram oxygen 



Such an oxido-reduction is possible because it leaves 

 a positive energy balance. The energy required to fix 

 the hydrogen to the acceptor is less than the energy 

 gained by dehydrogenation. This latter value (energy 

 from dehydrogenation) is quite uniformly 3.3 cal. per 

 gram of oxygen added (or for Ke gm. of hydrogen 

 removed), provided that the oxidation is complete. 



