ARS | Publication request: An insect herbivore microbiome with high plant biomass-degrading capacity

Submitted to: PLoS Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 19, 2010
Publication Date: September 23, 2010
Repository URL: http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1001129
Citation: Suen, G., Scott, J.J., Aylward, F.O., Adams, S.M., Tringe, S.G., Pinto-Tomas, A.A., Foster, C.E., Pauly, M., Weimer, P.J., Barry, K.W., Goodwin, L.A., Bouffard, P., Osterberger, J., Harkins, T.T., Slater, S.C., Donohue, T.J., Currie, C.R. 2010. An insect herbivore microbiome with high plant biomass-degrading capacity. PLoS Genetics. 6(9):e1001129.

Interpretive Summary: Fungus-cultivating leaf-cutter ants are the major organisms processing plant biomass in Central and South America, but the way they do this is not understood. We have demonstrated that the microorganisms in the ant colonies selectively degrade the cellulose from leaf material carried in by the ants. Analysis of the combined DNA from these ant colonies has revealed that the microbial cellulose-degrading community is very diverse, and that surprisingly the enzymes responsible appear to be more closely related to those of the cow rumen than to those of any other source. The results have identified several bacterial species that contribute most of the cellulose-degrading capability, and these bacteria may be a source of improved enzymes for use in biofuels production systems.

Technical Abstract: Herbivores can gain indirect access to recalcitrant carbon present in plant cell walls through symbiotic associations with lignocellulolytic microbes. A paradigmatic example is the leaf-cutter ant (Tribe: Attini), which uses fresh leaves to cultivate a fungus for food in specialized gardens. Using a combination of sugar composition analysis, metagenomics, and whole-genome sequencing, we reveal that the fungus garden microbiome of leaf-cutter ants is composed of a diverse community of bacteria with high plant biomass degrading capacity. Comparison of this microbiome’s predicted carbohydrate-degrading enzyme profile with other metagenomes shows closest similarity to the bovine rumen, indicating evolutionary convergence of plant biomass degrading potential between two important herbivorous animals. Given the recent interest in cellulosic biofuels, understanding how large-scale and rapid plant biomass degradation occurs in a highly evolved insect herbivore is of particular relevance for bioenergy.