Symbiosis
Symbiosis is a close relationship between beings of different species; in its narrowest sense it is to the benefit of both.
A well-known example are the lichens, consisting of a fungus in close symbiosis with either a green alga or a cyanobacterium (blue-green alga). The fungus gives a protected space for living to its autotroph partner and receives from it organic substance.
French: symbiose