Abstract
A total of six 16S rRNA targeted oligonucleotide probes were used to quantify Fibrobacter abundance and diversity in the gastrointestinal contents of a pony. Approximately 12% of the total 16S rRNA extracted from cecal contents hybridized with a Fibrobacter genus-specific probe and a Fibrobacter succinogenes species-specific probe. However, no significant hybridization was observed with a probe for the species. Fibrobacter intestinalis or with three probes for F. succinogenes subspecies. This suggested the presence of a previously undescribed population of F. succinogenes-like organisms. Novel lineages of F. succinogenes were subsequently identified by using PCR primers specific for the genus to amplify sequences coding for 16S rRNA from DNA extracted from cecal contents. Sequences of the cloned amplification products were shown to be affiliated with F. succinogenes but represented two distinct, and novel, lines of descent within the species.