How often have you heard of two or more bacterial species coexisting within the same cell of a host? It’s known to happen with some frequency in some amebas, insects and other invertebrates (including the strange case of the mealybug bacteria, which have an endosymbiotic bacterium that carries another bacterium inside it.) But how widespread are such ménages a trois/quatre/cinq or more outside these groups? One new example is the recently published account of two bacterial species coexisting within a single spore of a fungus. I’m talking about an arbuscular mycorrhizal fungus, Gigaspora margarita, whose cells carry a rod shaped bacterium of Burkholderia group called Candidatus Glomeribacter gigasporarum (CaGg) and coccoid one as yet nameless, related to the Mycoplasma. Neither bacterium has been cultivated.
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