Molecular profiling and identification of methanogenic archaeal species from rabbit caecum

During a comparison of 16S rDNA PCR-denaturant gradient gel electrophoresis (DGGE) profiles of methanogenic archaea from rumen fluid, rabbit caecum and pig feces, a unique band common to all rabbit caecum samples was observed. DGGE profiling also showed that the methanogen community from the New Zealand White adult rabbits is different and less complex than the methanogen communities from the rumen and pig feces. Small subunit ribosomal gene sequences of methanogenic archaea were subsequently retrieved from the constructed rabbit caecum 16S rDNA gene library. Results of the phylogenetic analysis indicated that rabbit caecum is inhabited by members of the genus Methanobrevibacter and is possibly one-species dominated, because all the retrieved sequences exhibited similarity values of 99% or higher. This species may well be a novel species of the genus Methanobrevibacter. It belongs to a distinct phylogenetic group containing Methanobrevibacter woesei, Methanobrevibacter thaueri and Methanobrevibacter gottschalkii strains isolated from animal feces, and Methanobrevibacter smithii from the predominating methanogen population of the human large bowel.