Detection of Proteobacteria from the rumen by PCR using methanotroph-specific primers

To detect Proteobacteria, including methanotrophs, from the rumen fluid and the bacteria inhabiting the rumen epithelium.

Proteobacteria inhabiting the rumen were detected by PCR using methanotroph-specific primers. The detected Proteobacteria were divided into clusters A, B, and C in addition to one clone, which was distinct from the clusters and closely related to Nitrosomonas sp. The clusters A, B, and C were close to Succinivibrio dextrinosolvens, Enterobacter cloacae, and Actinobacillus minor, respectively. The clones obtained from the rumen fluid each belonged to cluster A or B. The clones obtained from the rumen epithelium belonged to cluster B or C or to Nitrosomonas sp.

It has been assumed that the rumen fluid and the rumen epithelium host different populations of Proteobacteria. Moreover, detection of Nitrosomonas from the rumen epithelium would indicate the possibility that the bacterium oxidizes ammonia and methane on the rumen surface.

These findings suggest that the rumen fluid and the epithelium support different microbial populations, which would play specific roles in rumen function. Future study should focus on the relationship between these communities and physiological functions in the rumen.