Abstracts (first author)
The gut microbiome of fungus-growing termites expresses two orders of magniture more decomposition genes than the termites of their fungus-garden symbiont
Fungus-growing termites (Macrotermitinae, Blattodea) live in mutualistic symbiosis with a Termitomyces fungus (Tricholomataceae, Basidiomycotina), which aids in the degradation of plant material and is reared on a special substrate (the fungus comb) maintained by the termites through the incorporation of plant material after passage through the termite guts. The association with crop fungi has made this termite sub-family one of the major decomposers in the Old World tropics. It has been suggested that also termite gut microbes may contribute carbohydrate-active enzymes (CAZymes) that aid in the breakdown of plant substrate, but verification of this contention has only recently become technically feasible. We have sequenced a Macrotermes natalensis genome (1.3 GB), the associated Termitomyces fungal genome, and a set of caste-specific gut microbiomes of termites to characterize bacterial CAZymes contributions of microbiomes relative to the potential of termites and fungus. We identified 86 termite and 211 Termitomyces CAZyme genes, but found surprisingly high numbers of bacterial CAZyme genes in the worker and soldier gut microbiomes (13903 and 11902, respectively). The CAZymes of bacteria and Termitomyces appear to be complementary, suggesting division of labour between the fungal and bacterial symbionts, with gut bacteria decomposing mostly short chain sugars after Termitomyces has broken down the recalcitrant larger carbohydrates. The gut microbiome of the queen was markedly different and almost completely devoid of plant decomposition enzymes, suggesting a high-nutrient diet consisting of only Termitomyces fungus material. These results shed completely new light on the fungus-growing termite symbiosis, reducing the role of termites to being merely the managers of multicomponent microbial/fungal bioreactor systems in their gardens and guts.