Isozyme and morphological characteristics of the anaerobic fungus Piromyces mae isolated from the duodenum, rumen and faeces of sheep

The role of anaerobic gut fungi in ruminants

Anaerobic chytridiomycete fungi are found in the gastrointestinal tracts of sheep, cattle and goats, as well as in many other domesticated ruminant and nonruminant herbivores and a wide variety of wild herbivorous mammals. They are principally found associated with the fibrous plant particles of digesta and as free swimming zoospores in the fluid phase. The presence of large fungal populations in animals consuming mature pasture or diets largely composed of hay or straw together with the production of highly active fibre degrading enzymes lead to' the belief that anaerobic fungi may have a significant role to play in the assimilation of fibrous feeds by ruminants. While many early studies focused on anaerobic fungi because of their unusual biology and metabolism, the large part of subsequent research has emphasized the biotechnological potential of their cellulases, xylanases and phenolic esterases. In recent years, the extent of the contribution of anaerobic fungi to the nutrition of ruminants has also been established through studies of fungal populations in the rumen and the dietary factors which influence them, as presented in this review. Further, we discuss the evidence supporting an important contribution of anaerobic fungal populations in the rumen to feed intake and digestion of poor quality feed by domesticated ruminants. In conclusion, the review explores some different methods for manipulating fungi in the rumen for increased feed intake and digestion.

Diversity of anaerobic gut fungal populations analysed using ribosomal ITS1 sequences in faeces of wild and domesticated herbivores

Gut fungal-specific PCR primers have been used to selectively amplify the ITS1 region of gut fungal rDNA recovered from faeces of domestic and wild animals to investigate population diversity. Two different gel-based methods are described for separating populations of gut fungal rDNA amplicons, namely (1) denaturing gradient gel electrophoresis (DGGE) and (2) separation according to small size differences using Spreadex, a proprietary matrix for electrophoresis. Gut fungal populations were characterised by analysis of rDNA in faeces of seventeen domesticated and ten wild herbivores. Sequences derived from these gel-based characterisations were analysed and classified using a hidden Markov model-based fingerprint matching algorithm. Faecal samples contained a broad spectrum of fungi and sequences from five of the six recognised genera were identified, including Cyllamyces, the most recently described gut fungal genus, which was found to be widely distributed in the samples. Furthermore, four other novel groupings of gut fungal sequences were identified that did not cluster with sequences from any of the previously described genera. Both gel- and sequence- based profiles for gut fungal populations suggested a lack of geographical restriction on occurrence of any individual fungal type.