Mixotricha paradoxa is not a bacterium. Like many of the microbes in termite guts, it is a large protozoan, half a millimetre long or more, and large enough to contain hundreds of thousands of bacteria inside itself—as we shall see. It lives nowhere except in the gut of Darwin’s termite, where it is a member of the mixed community of microbes that thrive on the wood chips milled by the termite’s jaws.
