Characterization of proteins critical to fungal cellulosome assembly for Anaeromyces robustus, Neocallimastix californiae and Piromyces finnis (cellulosomes are multi-protein complexes that tether plant biomass degrading enzymes together). These findings suggest that the fungal cellulosome is an independently evolved fungal complex that co-opted useful activities from bacterial neighbors within the herbivore rumen microbiome.