In the master thesis, we characterized 11 strictly anaerobic strains isolated from the sheep rumen in Slovenia during a two-month period. The studied strains belonged to the genus Prevotella and formed six putative species. One of the species, comprising six studied strains and two other strains isolated in Japan, was selected for a formal species description. Using whole genome sequences, we found that two strains, isolated at two time points, were identical. The other strains formed clearly diverged intraspecies lineages. Other studied strains belonged to five new Prevotella species, which we confirmed by comparison with all known gut and ruminal strains of the genus. We examined the ability of all six species to degrade plant polysaccharides and discovered that each putative species utilizes a different set of polysaccharides. The capability of polysaccharide utilization is predicted to be one of the essential Prevotella adaptations. The diversity of nutrient usage likely contributes to decreasing the competition between species. The strains from the new species degraded xylans and pectins but not starch, which is unexpected for Prevotella. One of the strains lost its ability to degrade inulin, which was explained also by genomic analysis. The strains of the new species produced succinate and acetic acid fermentatively and did not grow in presence of bile acids, as is typical for Prevotella. We used API tests and the membrane long chain fatty acids profiles to describe differential markers that clearly distinguish the new Prevotella species from the previously described species. The new species was common in the rumen, as it was found in all studied metagenome samples of cattle and sheep. With the thesis, we aimed to expand the collection of cultured and characterized ruminal Prevotella species, because despite their abundance, there are currently only 5 published isolated rumen species.
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