You have heard of the leaf-cutting ants1 that meticulously cultivate "their" fungi2 which provide them with nutrients, and that, in addition, host actinobacteria which prevent bacterial and fungal infections of their fungi as well as their own infection by an entomopathogenic fungus3 Metarhizium anisopliae. No big surprise, other insects stick to high standards of health care too.
One new example is the recently published account of three different genera of beewolf wasps that cultivate Streptomyces bacteria — producing at least nine antimicrobial compounds — for protection against pathogenic fungi (beewolves were intrduced to this blog way back in 2007 here). The observation that these 'Candidatus Streptomyces philanthi' (CaSP) symbionts belong to one single distinct clade but are found in three beewolf genera prompted a more detailed phylogenetic analysis, which led to the conclusion that — in all likelyhood — this symbiosis was already established in the Cretaceous period for which various fossiles of beewolves4 are known.
Click "source" to read more.