Ruminants symbiosis

Recall that the original development of eukaryotic creatures may have started with a symbiotic relationship between two prokaryotes and that symbiosis between algae and nonphotosynthetic organisms may have led to development of higher plants. Associations between species are still important today. For example, the bacteria in the protozoa of the digestive tract of ruminant animals are essential to production of meat. Our own bodies play host to bacteria, fungi,... 

Not all animals obtain the essential amino acids from plants. Some (the ruminants) can by-pass the main route by direct assimilation of the amino acids produced by symbiotic bacteria in the gut. These bacteria can break down cellulose, the main structural carbohydrate of plants, and can also synthesise all the amino acids, required for their growth and development, from a simple fixed-nitrogen source. The ruminant obtains its more complex nitrogen requirements by digestion of dead bacteria. (Goats, for example, can survive on a diet of hay and ammonia.) This may appear to be a somewhat one-sided symbiosis, with the bacteria carrying out all the important functions but, in return, the bacteria obtain from the animal a copious supply of carbohydrate and are maintained in a favourable environment with respect to temperature and medium composition. 

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