Anaerobic fungi (phylumNeocallimastigomycota): advances in understanding their taxonomy, life cycle, ecology, role and biotechnological potential

Abstract

Anaerobic fungi (phylum Neocallimastigomycota) inhabit the gastrointestinal tract of mammalian herbivores, where they play an important role in the degradation of plant material. The Neocallimastigomycota represent the earliest diverging lineage of the zoosporic fungi; however, understanding of the relationships of the different taxa (both genera and species) within this phylum is in need of revision. Issues exist with the current approaches used for their identification and classification, and recent evidence suggests the presence of several novel taxa (potential candidate genera) that remain to be characterised. The life cycle and role of anaerobic fungi has been well characterised in the rumen, but not elsewhere in the ruminant alimentary tract. Greater understanding of the 'resistant' phase(s) of their life cycle is needed, as is study of their role and significance in other herbivores. Biotechnological application of anaerobic fungi, and their highly active cellulolytic and hemi-cellulolytic enzymes, has been a rapidly increasing area of research and development in the last decade. The move towards understanding of anaerobic fungi using -omics based (genomic, transcriptomic and proteomic) approaches is starting to yield valuable insights into the unique cellular processes, evolutionary history, metabolic capabilities and adaptations that exist within the Neocallimastigomycota.

The Enigmatic Universe of the Herbivore Gut

“…The anaerobic fungi found in the herbivore gut are members of a basal group of fungi (Neocallimastigomycota) and are characterized by forming zoospores (motile asexual spores) and rhizoids ( Figure 1). They also lack mitochondria but contain hydrogenosomes, where ATP is synthesized [2]. In the environment of the gut, these anaerobic fungi partner with methanogenic archaea to synergistically deconstruct lignocellulose.…”

“…Although anaerobic fungi comprise only a fraction of the gut microbiome in herbivores ( 8%), they are believed to be important players in the deconstruction of plant biomass, through a combination of enzymatic deconstruction and physical disruption via invasive growth of the rhizoids [2] (Figure 1). However, unlike many of the prokaryotic species identified in the herbivore gut by metagenomic analyses [4], most of these anaerobic fungi are cultivatable.…”

In Silico Identification of Microbial Partners to Form Consortia with Anaerobic Fungi

“…Moreover, they possess the highest diversity of lignocellulolytic enzymes, largely untapped, within the fungal kingdom [13]. These organisms play a pivotal role in the digestion of plant biomass in herbivores, due to the physical and chemical way in which they degrade plant biomass [14]. Recent work highlights the bounty of biotechnological applications of these fungi [15].…”

Buwchfawromyces eastonii gen. nov., sp. nov.: a new anaerobic fungus (Neocallimastigomycota) isolated from buffalo faeces

“…At present six genera of anaerobic fungi are recognised, differentiated by thallus morphology and zoospore flagellation (Gruninger et al 2014). However, the lack of other reliable morphological features, combined with difficulties in the cultivation of these fungi, exchange of cultures between different labs and their morphological variability in culture, has hindered more definitive study of their diversity.…”