Potential for Nitrogen Fixation in the Fungus-Growing Termite Symbiosis.

Termites host a gut microbiota of diverse and essential symbionts that enable specialization on dead plant material; an abundant, but nutritionally imbalanced food source. To supplement the severe shortage of dietary nitrogen (N), some termite species make use of diazotrophic bacteria to fix atmospheric nitrogen (N). Fungus-growing termites (subfamily Macrotermitinae) host a fungal exosymbiont (genus ) that provides digestive services and the main food source for the termites. This has been thought to obviate the need for N-fixation by bacterial symbionts. Here, we challenge this notion by performing acetylene reduction assays of live colony material to show that N fixation is present in two major genera ( and ) of fungus-growing termites. We compare and discuss fixation rates in relation to those obtained from other termites, and suggest avenues of research that may lead to a better understanding of N fixation in fungus-growing and other termites.