(a) Macrotermes natalensis fungus-growing termite colony. (b) A close up of the fungus comb (courtesy of Duur K. Aanen), generated by the termites through a mix of plant biomass and Termitomyces spores after termite gut passage, likely allowing for gut bacteria to control what enters the fungus comb. (c) In the absence of termites, the fungus comb is rapidly over-grown by Pseudoxylaria. (d–f) In vitro growth characteristics of three fungi isolated from M. natalensis fungus combs: (d) Pseudoxylaria, (e) Trichoderma and (f) Coriolopsis ((e) and (f), courtesy of Saria Otani).