Equine anaerobic fungi: Key taxa of central importance to dietary fibre degradation

The hindgut microbiota of equines enables the degradation of dietary fibre, as the equine host lacks this enzymatic capability. The hindgut microbiota is comprised of five main groups of microbes: bacteria, anaerobic fungi, protozoa, archaea and viruses (Julliand & Grimm, 2016). Despite this, however, only bacteria tend to be routinely studied when analysis of the hindgut microbiota is undertaken. This is short-sighted, as anaerobic fungi play a unique role in fibre degradation. This is due to their combined invasive growth and potent enzymatic activity enabling them to disrupt plant structural barriers and access internal areas of the plant tissue that other microbes cannot (Orpin, 1975; Ho et al., 1988; Solomon et al., 2016). In addition to being the most effective fibre degraders in the herbivore gut (Lee et al., 2000), they also benefit other gut microbes by increasing the plant surface area available for them to colonise.