From Big Medical Encyclopedia

SYMBIONTS (Greek syn together + bion, biontos living) — the organisms of different types which are in close cohabitation which cannot exist separately from each other and are closely connected by both the general house, and the derived benefit of such cohabitation. As an example of the mutual benefit brought each other two S. the lichen representing two S.' set — a mushroom and an alga can serve. Skin, perigastriums and internals of the person serve as a habital of bacteria, fungi, the elementary organisms, a part to-rykh is harmless to an organism of the owner — commensals (see. Commensalism ), a part — potential parasites (see. Parasitism ), and a part useful — producers, enzymes necessary to an organism of the owner (urease, uricase), vitamins of group B, etc. In the latter case speak about a mutualism. Nek-rye S. promote development of antibodies, napr, flora of maternal milk (Bifidus) protects newborns from infection with pathogenic microbes.

There is an assumption that nek-ry organellas of cells of eukaryotes, such as mitochondrions, chloro-layers, originally were symbiotic organisms only later, at some stage of process of evolution, entered a cell as a necessary component (see. Eukariotny organisms ).

See also Parazitotsenoz , Symbiosis .

Bibliography: See bibliogr. to St. Symbiosis .

A. N. Alekseev.