CHAPTER VI 



NUTRIT ION OF MICROORGANISMS AND THE ROTATION or ELEMENTS 



IN NATURE* 



All organic matter on earth is undergoing continuous change. Or- 

 ganisms grow and decay. The same carbon and nitrogen atoms which 

 constitute the organic world of to-day constituted it thousands of 

 years ago. The amount of carbon, nitrogen, hydrogen and of all 

 other elements of life on earth is limited, and the same atoms will 

 be used for the future generations of life that constitute the present. 

 There must be continuous destruction to enable new construction. 

 Construction is mainly the task of green plants, enabled by the chloro- 

 phyl to use the energy of sunlight in building up organic substances 

 from minerals, water and carbon dioxide. Destruction is caused 

 mainly by animals and other organisms which have to break down 

 organic matter in order to exist. These two factors keep the atoms of 

 the organic world in perpetual rotation. 



In this circulation of the elements it is necessary that all compounds 

 of organic nature be decomposed finally to a form available for plant 

 food. If this were not the case, the indestructible compound would 

 sooner or later accumulate in such enormous quantities that the 

 elements constituting this body would be removed entirely from 

 general circulation. Let us suppose, as an illustration, that for some 

 unknown reason, all urea bacteria on earth would die. Urea could be 

 decomposed no more, and the plants, unable to use urea as a source of 

 nitrogen in place of nitrates, would get but little benefit out of stable 

 manure. All urea would pass gradually undecomposed into rivers, 

 lakes, and finally into the ocean where it would accumulate con- 

 tinuously. The enormous quantities of nitrogen taken out of cir- 

 culation would cause a decreasing growth of plants, and life would 

 soon cease because of lack of nitrogen. For this reason all products of 

 living organismsjnust be further broken up by some other organisms, 



* Prepared by Otto Rahn. 



258 



