(785a) Bottom-up Construction of Synthetic Microbial Pairs Inspired By Nature

Anaerobic fungi in the hindgut of large herbivores are among the most robust organisms at degrading crude lignocellulose. Though gut fungi have been characterized in isolation, such growth does not accurately mimic their native environment. Anaerobic fungi exist in nature as part of much larger consortia, which include archaea, bacteria, and protozoa. In particular fungi form a tight interaction with methane producing archaea (methanogens), which siphon hydrogen and other metabolites from the fungi. This syntrophic partnership allows the fungi to more efficiently produce energy by increasing the flux through their hydrogenosomes. In addition to greatly increasing biomass degradation, fungi-methanogen co-cultures are capable of directly converting crude biomass into methane. Elucidating this specific interaction using â??OMICS-based approaches will allow for the design of stable consortia capable of efficiently converting biomass to value-added products.

In this work, native co-cultures of anaerobic fungi and methanogenic archaea were isolated from herbivore fecal materials. These co-evolved consortia demonstrated approximately 2-3 fold increased accumulation of fermentation gases and degradation of biomass compared to cultures with the methanogens removed. Natural consortia were remarkably stable in batch culture, surviving together for over 18 months and 150 transfers. Genomic sequencing of the methanogens in this consortia revealed two distinct species of methanogens in the genera Methanosphaera and Methanocorpusculum. The sequences were assembled and analyzed using the Kbase platform, and then binned into separate genomes. Synthetic co-cultures were created using well-characterized anaerobic fungi and methanogens inspired by the genomic analysis of the native mixture and capable of converting a range of different substrates to methane. The synthetic co-cultures were tested for substrate consumption and stability on a variety of substrates including reed canary grass, avicel, xylan, and pectin. Synthetic co-cultures displayed accelerated growth and degradation of substrates, on par with the native consortia, and enabled fungi to metabolize an expanded array of substrates (e.g. pectin and xylan) that the fungi could not metabolize in isolation. This work demonstrates that mixed-and-matched microbial pairs can perform equally well at converting crude biomass into syngas products as those co-evolved in nature.