182 PHYSIOLOGY OF BACTERIA 



mol of sugar has not the full benefit of the 685,800 calories, but can 

 use only 98.3% of that amount. In the oxidation of methane to 

 COo and H2O, the loss is 9%. 



While these losses towards the entropy may eventually 

 be fairly large in inorganic processes, it seems that they 

 are rather small in the organic reactions ordinarily met 

 with in biological processes. Thus, the error in assuming 

 the free energy to equal the differences of combustion 

 heats between substrate and products is not very great, 

 and amounts perhaps to a few per cents of the total 

 energy liberated. For most fermentations, this per- 

 centage is not known. A good survey on the autotrophic 

 bacteria in their energy requirements is given by Baas- 

 Becking and Parks (1927) and a detailed discussion of 

 the theory is offered by Buchanan and Fulmer (1928- 

 30). 



Realizing that the energy liberated is not identical 

 with the available energy for construction purposes, 

 but in most cases approximately so, the next question 

 will be that of efficiency: how much of the available 

 energy is actually used for growth? This has been 

 computed for some of the autotrophic bacteria by Baas- 

 Becking and Parks (1927). The percentage of the 

 available energy stored in the new growth is the efficiency. 

 This efficiency seems very low. The following maximum 

 efficiencies were found by Baas-Becking and Parks : 



Table 43. — Amount of Available Energy Utilized for Growth 



Per cent 



Hydrogenomonas 26 



Methanomonas (maximum efficiency) 33 . 8 and 25 . 5 



Methanomonas (minimum) 0.6 



Nitrohacter and Nitrosohacter 6 



Thiobacillus denitrificans 9 



Sulfur bacteria, probably about 8 



