Ecology of Prokaryotic Microbes in the Guts of Wood- and Litter-Feeding Termites

Abstract

The gut of wood-and litter-feeding tennites harbors a dense and diverse community of prokaryotes that contribute to the carbon, nitrogen and energy requirements of the insects. Acetogenesis from H 2 plus CO 2 by hindgut prokaryotes supports up to 1/3 of the respiratory requirement of some termite species; and Nrfixing and uric acid-degrading microbes can have a significant impact on termite N economy. Microclcctrode studies reveal that hindguts consist of an anoxic lumen surrounded by a mierooxic periphery ~ a finding consistent with the occurrence of both anaerobic and Oz-dependent microbial melabolism in hindguts. They also suggest that the enigmatic dominance of acetogens over l11cthanogens as an H 2 "sink" reflects a spatial separation of these Hrconsuming populations, with the former being closer to sources of H 2 production. Isolation of a number of the prokaryotes (including spirochetes, which have proven to be H2/COz-acetogens) reveals that termite guts are a souree of novel microbial diversity. However, molecular biological analyses indicate that much of that diversity is still poorly represented. in culture.