Anaerobic gut fungi are found in the digestive tract of large herbivores, where they comprise a small fraction of the rich rumen microbiome. In this niche, they have evolved to break down plant biomass through filamentous growth and the secretion of powerful enzymes (cellulases) that convert cellulose into sugar. In contrast to their native environment, fungi that are grown in isolation readily ferment sugars into ethanol and other products. We are developing new tools to control biomass degradation and endogenous ethanol production in gut fungi by tuning environmental factors that affect cellulase and cellulosome (multi-enzyme complex) production. To accomplish this goal, we have isolated a panel of anaerobic fungi from the Piromyces, Neocallimastix, and Anaeromyces genera, and have measured cellulase regulation by RNAseq and biochemical approaches for a variety of growth substrates. Overall, we have found that fungal cellulosomes are regulated at the post-transcriptional and post-translational level in the presence of simple sugars, leading to dynamic, tunable cellulosomes that optimize biomass breakdown. In addition, we have observed that nutrient-starved fungi produce unique secondary metabolites. We hypothesize that these metabolites regulate the action of other rumen microbes, which increases the residence time of fungi within the rumen.

Engineering anaerobic gut fungi for the production of fuels and bioactive compounds

247th National Meeting (2014)

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