Fungal microbiome: what do we know about endohyphal bacteria?

Abstract

Over two decades ago the first endohyphal bacteria were described. They were observed in the hyphae of Mucoromycota representatives, an evolutionarily old fungal lineage. Since then, such interactions have been studied and new types of endohyphal bacteria are being found in various fungal groups. These relationships are as diverse as the organisms involved. They differ in evolutionary history as some partners coevolve for hundreds of millions of years while others interact spontaneously. Some of the partnerships are more mutualistic and some are classified as mild parasitism. Moreover, some endosymbionts cannot live outside of their host, others control their host’s reproduction, while others engage in fully facultative, spontaneous interactions when it is beneficial for them. We are still far from understanding this phenomenon, but the progress in molecular and microscopy techniques, as well as growing interest in the biology of these multifaceted interdomain interactions, brings us closer to achieving this goal.