Their ability to degrade lignocellulose gives termites an important place in the carbon cycle. This ability relies on their partnership with a diverse community of bacterial, archaeal and eukaryotic gut symbionts, which break down the plant fibre and ferment the products to acetate and variable amounts of methane, with hydrogen as a central intermediate. In addition, termites rely on the biosynthetic capacities of their gut microbiota as a nutritional resource. The mineralization of humus components in the guts of soil-feeding species also contributes to nitrogen cycling in tropical soils. Lastly, the high efficiency of their minute intestinal bioreactors makes termites promising models for the industrial conversion of lignocellulose into microbial products and the production of biofuels.