Anaerobic gut fungi Caecomyces communis, Neocallimastix frontalis and Piromyces spp. nov., have distinct effects on plant fibres during digestion.

Anaerobic gut fungi are the first colonizers of plant materialthat enters the digestive system of ruminants. However,it unclear how different fungal species contribute tothe ability of the rumen microbiome to convert feed tonutrients. Here, we isolated three species of anaerobic fungi,including the novel Piromyces edwardsiae. We investigated ifthese species have distinct roles in the digestion of fibrousfeed components, through assessment of changes caused toplant material itself. We found Neocallimastix frontalis isolateCoB3 and P. edwardsiae isolate SHC digested plant materialsmore effectively than Caecomyces communis isolate SHB. Thethree fungi had distinct effects on feed composition. N.frontalis CoB3 degraded hemicelluloses and cellulose to asimilar extent, P. edwardsiae SHC preferentially degradedhemicellulose, while C. communis SHB preference dependedon the substrate. From the panel of monosaccharides thatmay result from such degradative activity, all fungi consumedonly glucose, suggesting involvement of mechanisms morecomplex than only fungal carbon source usage. Overall,this indicates that each of these fungal species has distinctroles in the degradation of plant material and differentniches in the rumen. Exploring these roles creates afunctional understanding of the rumen microbiome, criticalfor developing more sustainable agriculture.