Phylogenetic analysis of yeast in the rumen contents of cattle based on the 26S rDNA sequence

Abstract

The composition of yeast communities in the rumen of cattle was investigated using comparative DNA sequence analysis of yeast 26S rDNA genes. 26S rDNA libraries were constructed from rumen fluid (FF), rumen solid (FS) and rumen epithelium (FE). A total of 97 clones, containing a partial 26S rDNA sequence of 0·6 kb length, were sequenced and subjected to an on-line similarity search.The 41 FF clones could be divided into five classes. The largest class was affiliated with Pezizomycotina class (85·4% of clones), and the remaining classes were related with the Urediniomycotina (2·4%), Hymenomycetes (4·9%), Ustilaginomycetes (4·9%) and Saccharomycotina (2·4%) classes. The 26 FE clones could be divided into three classes and the Saccharomycetes class (92·4% of clones) was the largest group. The remaining classes were related with either Pezizomycotina (3·8%) or Ustilaginomycetes (3·8%). The 30 FS clones were all affiliated with Saccharomycotina. Saccharomycotina were predominant in rumen epithelium and rumen solid while Pezizomycotina were predominant in rumen fluid. Yeast belonging to the Saccharomycotina class was predominant in the rumen as a whole (57%). One clone (FF34) had less than 90% similarity to any sequence in the database and was thus apparently unrelated to any previously described yeast.