112 NUTRITION AND METABOLISM. 



the products of which have not yet been analyzed. The calcium salt of 

 lactic acid gives with B. bulylicus butyric acid with a little acetic acid. 



FATS are esters of glycerin with fatty acids. They can be hydrolyzed, 

 like all esters, and thus give free acids and glycerin. The following 

 equation shows the hydrolyzation (saponification) of tristearin: 



(C 18 H 35 O 2 ) CH 2 + H 2 O C 18 H 35 O 2 H CH 2 OH 



I I 



(C 18 H 35 2 ) - CH + H 2 = C 18 H 35 2 H+ CHOH 



I I 



(C 18 H 35 2 )-CH 2 +H 2 C 18 H 35 2 H CH 2 OH 



Tristearin Stearic acid Glycerin 



Only a few microogranisms are able to decompose fat to glycerin and 

 fatty acids, and these appear to be the only organisms which can destroy 

 fat. This saponification is the only known method of fat decomposition. 

 After this first step is accomplished, the glycerin and acids are open to 

 decomposition by the methods described above, either by complete 

 combustion or otherwise. The most significant change, perhaps, in 

 the decomposition of fat is a production of free acids from the neutral 

 fat molecule. 



There are still a few compounds occurring in nature which should be 

 considered, inasmuch as they are products of bacterial activity, and are 

 more or less constantly forming. The most important ones are methane 

 and hydrogen. Both of these gases are used by certain bacteria in a 

 very unusual metabolism as a source of energy. 



B. methanicus (or B. oligocarbophilus) oxidizes methane completely. 



This organism requires no other organic food. It is retarded or inhibited 

 by organic substances since it takes the carbon only hi form of methane 

 or carbon dioxide and the nitrogen only in mineral form as nitrate or 

 ammonia. In its life requirements, it resembles very much the nitrate and 

 sulphur bacteria. This bacillus is also able to oxidize carbon monoxide 

 to dioxide and to get all the necessary food and energy supply: in this way. 

 The "hydrogen" bacterium is called B. pantothropus by its discoverer 

 because it is able to live on ordinary laboratory media as well. If no 

 other substance is available, it will oxidize hydrogen. This oxidation 

 does not occur directly, as would be expected, following the equation 



