CHAPER VI 



THE NUTRITION OF THE AUTOTROPHIC 

 BACTERIA 



THE autotrophic bacteria are tho.se which thrive on 

 the simplest of inorganic compounds as sources of 

 energy, carbon and nitrogen. Like plants they are 

 independent of other organic matter for their growth-. 

 They derive their carbon from carbon dioxide and their 

 nitrogen from ammonia, nitrates or nitrites. The energy 

 necessary for their groAvth and reproduction is obtained 

 in one of two ways. The photosynthetic autotrophs 

 utilise radiant energy from the sun. The chemosynthetic 

 autotrophs are able to grow in the dark and obtain the 

 energy required for the assimilation of carbon and 

 nitrogen by means of certain simple chemical reactions. 



The autotrophs and the metabolically closely related 

 blue -green algae and unicellular green plants may be 

 grouped as shown in Table 4 (p. 68). 



It has been suggested that, as these organisms use 

 very simple substances for their metabolism, they are 

 the primitive types of bacteria which were first developed 

 on the Earth before more complex organic nutrients 

 were available, and that the bacteria which have more 

 complicated requirements have been gradually evolved 

 from them as a result of changing conditions. 



The autotrophic bacteria contain protoplasm and other 

 cell constituents very similar to those found in what 

 we regard as being ordinary bacteria. Obviously, then, 

 they must be capable of very complex synthetic reactions 

 in order to build up such compounds from the simple 

 raw materials carbon dioxide and ammonia, 



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