These results suggest the predominance of uncultured Treponema th

These results suggest the predominance of uncultured Treponema that appear to have distinct members related to the digestion of either selleck inhibitor hay or concentrate diet. The distribution of spiral-shaped bacteria (spirochetes) and their role in the degradation

of plant material in the rumen have been reported by different workers (Bryant, 1952; Stanton & Canale-Parola, 1979; Ziolecki & Wojciechowicz, 1980). Direct microscopic enumeration of spirochetes showed up to 2.0 × 108 cells mL−1 of bovine rumen fluid (Stanton & Canale-Parola, 1979), which is comparable to the population density of common rumen bacterial species (Bryant & Burkey, 1953). All strains of spirochetes isolated from the rumen have been classified in the genus Treponema, comprised of three described species: Treponema bryantii (Stanton & Canale-Parola, 1980), Treponema saccharophilum (Paster & Canale-Parola, 1985) and Treponema zioleckii (Piknova et al., 2008). Rumen Treponema strains are able to degrade plant polysaccharides (Ziolecki, 1979), and in vitro studies have shown a beneficial interaction of T. bryantii with the cellulolytic bacterium Fibrobacter succinogenes (Stanton & Canale-Parola, 1980). Recent application of molecular techniques in the study of microbial ecology demonstrated the existence of a considerable proportion of diverse uncultivated spirochetes involved in chronic disease in the human oral cavity and in degradation of lignocellulose materials in the termite gut (Paster et al., 1996, 2001; Dewhirst et al., 2000). For example, 16S rRNA gene-based clone library analysis of samples from the oral cavity of a human subject and from the hindgut of a single

termite species, respectively, suggested some 20 and 23 new species of spirochetes (Choi et al., 1994; Lilburn et al., 1999). Considering the individuality of human microbiota and the existence of ∼280 termite genera, these observations suggest the presence of a selleck kinase inhibitor considerable diversity of spirochetes, particularly uncultured members. In contrast to the above digestive tract environments, our knowledge of the uncultured Treponema community in the rumen is very limited. The current understanding of the rumen Treponema diversity is mainly based on earlier cultivation-based studies that showed morphological and physiological variations in rumen spirochetes (Paster et al., 1991; Piknova et al., 2008). A comprehensive analysis of 16S rRNA gene sequences derived from the rumen showed that rumen Treponema were not detected frequently (Edwards et al., 2004; Yang et al., 2010). However, we had previously retrieved a number of Treponema clones related to both cultured and uncultured members from a fiber-associated community (Koike et al., 2003; Shinkai et al., 2010). Based on these data, we speculated that rumen Treponema diversity has been underestimated and members of this group may play a metabolic role in fiber degradation.

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