Injecting bacteria into fungal hosts establishes stable endosymbiosis

Eukaryotes often host prokaryotic cells inside their own cells. Hosts of such ‘endosymbionts’ can rely on these organisms for metabolism or the production of other necessary molecules. For example, eukaryotes usually host bacterially derived mitochondria, and many host chloroplasts, both of which enable eukaryotic metabolism. More recently evolved intracellular bacteria, such as Wolbachia and Buchnera species in insect cells, are also common. Recent endosymbioses include bacteria living inside fungal cells (endohyphal bacteria), which can have a range of effects on host fitness, including mutualism. For example, some strains of the plant pathogenic fungus Rhizopus microsporus depend on the endosymbiotic bacterium Mycetohabitans rhizoxinica to sporulate; the symbiont also produces a toxin helpful for infecting plants and deterring fungus-eating predators. Endohyphal bacteria are an emerging topic in microbiology. Open questions in bacterial–fungal endosymbioses include how bacteria first establish in fungal cells (hyphae) and how stable symbioses evolve. A recent study by Giger et al. describes techniques to manipulate bacteria in hyphae that facilitate detailed study of this interaction.