syn·tro·phism 
(sĭn-trōfĭz′əm) also syn·tro·phy (sĭntrə-fē)
(sĭn-trōfĭz′əm) also syn·tro·phy (sĭntrə-fē)n.
A biological relationship in which microorganisms of two different species or strains are mutually dependent on one another for nutritional requirements.