ENERGY TRANSFORMATION 4l9 



containing 0.5 per cent asparagine, as a source of carbon and nitrogen. 

 These two elements were accounted for as follows: 



Assimilated by the bacteria. 



Given off as CO* or NH 3 



Non- volatile products 



Kruse calculated from these data that 19 per cent of the energy that was 

 made available from the decomposition of the asparagine had been 

 utilized by the bacteria for the synthesis of bacterial protoplasm. 

 According to Rubner, 72 the relative energy utilization of bacteria is 

 independent of temperature. The total amount of energy transformed 

 depends, however, largely on the temperature of growth, as shown in 

 table 29. The data were obtained by growing Bad. vulgare in 500 cc. 

 portions of 6 per cent meat extract solution. Rubner found that aerobic 

 bacteria are capable of utilizing 30.8 to 11.6 per cent of the energy 

 transformed, pathogenic bacteria the least. The thermophilic bac- 

 teria utilized 24.9 per cent of the energy. 



Linhart 73 calculated that only about 1 per cent of the total available 

 energy in mannite is utilized by Azotobacter for the fixation of nitrogen. 

 This was based upon the assumption that Azotobacter fixes 10 grams 

 of nitrogen for every gram of mannite decomposed and that all the 

 mannite is converted into C0 2 . No allowance was made for the forma- 

 tion of intermediary products or the synthesis of microbial protoplasm. 



When amino acids are used as sources of energy, the process of 

 synthesizing microbial protoplasm is a very economical one in which 

 little energy is wasted. This is true for fungi 74 and bacteria. Bad. 

 coli was found 76 to be able to utilize the energy of amino acids three to 

 eight times more effectively than that of glucose. According to Czapek 



72 Rubner, M. Energieverbrauch im Leben der Mikroorganismen. Arch. 

 Hyg., 48: 260-311. 1903; Die Beziehungen zwischen Bakterienwachstum und 

 Konzentration der Nahrung (Stickstoff und Schwefelumsatz). Ibid., 67: 161— 

 192. 1906; Energieumsatz im Leben einiger Spaltpilze. Ibid., 57: 193-243. 



73 Linhart, G. A. The free energy of biological processes. Jour. Gen. 

 Physiol., 2: 247-251. 1920. 



74 Czapek, 1902 (p. 502). 



76 Shearer, C. On the amount of heat liberated by B. coli when grown in the 

 presence of free amino acids. Jour. Physiol., 55: 50-60. 1921. 



