Why Sequence Microbes in a Termite's Gut?

A long-standing mission for DOE is to replace fossil fuels with renewable sources of cleaner energy, such as hydrogen produced from plant biomass fermentations. Termites efficiently transform the more abundant fractions of plant biomass (lignocellulose) as well as the more recalcitrant fractions of organic-rich soils (humic acids) to valuable metabolites (e.g. hydrogen and methane). They are able to do so by exploiting the diverse metabolic capabilities of microbial symbionts inhabiting their hindguts. A refined understanding of the microorganisms and the biochemical pathways they use within in the termite hindgut may therefore lead to more efficient strategies for converting biomass to useful fuels and chemicals. Similarly, an ability to harness the pathways directly involved in, or impacting upon hydrogen production in the termite gut may one day make biological production of this alternative energy source a viable application. This is a particularly attractive avenue to explore because many termite hindgut microbes appear to be hardwired for the conversion of plant-derived sugars into molecular hydrogen, even when operating in the background of high local hydrogen partial pressures. For perspective, the efficiency of termite hindgut microorganisms is such that they are capable of producing about 2 liters of hydrogen from fermentation of a typical sheet of (cellulose) printer paper.

These microbial ecosystems are simple in an unusual sense of the word, inasmuch as they are tiny (often less than one microliter in volume) and have distinct, concrete boundaries (the gut lining of their host insect). Yet, because of the huge reach and great abundances of their insect hosts globally, together these microbial ecosystems become major sites of catalysis of reactions that ultimately exert a huge impact on global carbon and nitrogen biogeochemistry, especially in tropical rainforests and similar biomes. Despite their mutually obligate interactions with their host, 80 years of study have revealed only a meager (albeit quite significant) understanding of the roles, functions, and identities of the majority of termite hindgut microbes. This project aims to make major inroads into achieving a better understanding of lignocellulose-processing termite gut microbiota.

CSP project participants: Jared R. Leadbetter (proposer, Caltech); Eric Mathur (Diversa); and Philip Hugenholtz, Natalia Ivanova, and Eddy Rubin (JGI).