Characterization of tannin-tolerant bacterial isolates from East African ruminants

Several tannin-tolerant bacteria were isolated from enrichment cultures of rumen microflora of bush duiker, giraffe, Grant's gazelle, sheep, and goat, and established in medium containing crude tannin extracts or tannic acid. The isolates were characterized by classical and molecular methods. The isolates were also tested for the presence of tannin acylhydrolase. Characterization by restriction fragment length polymorphism of the 16S rRNA-PCR product was performed with Alu1, Dde1, Msp1, and Taq1. Amplified fragment length polymorphism analysis was performed only on the isolates that were curved rods. The nucleotide sequence of PCR products derived from the 16S rRNA genes of isolates was determined. The classical characterization suggested that, with one exception all the curved rods isolates were Selenomonas and the coccus was a Streptococcus. Only Selenomonas-like isolates had tannin acylhydrolase activities. One isolate lost the ability to completely hydrolyze tannins after prolonged storage at –70 degree C. The restriction fragment length polymorphism profiles suggested that the Selenomonas-like isolates exhibited heterogeneity in the ribosomal RNA locus. The coccus had the same profiles as Streptococcus caprinus, while the straight rods appeared to be similar to each other. Amplified fragment length polymorphism analysis suggested that the Selenomonas-like isolates clustered into two major groups. The 16S rRNA sequences of the coccus clustered with that of Streptococcus species and the Selenomonas-like isolates exhibited a high level of similarity with Selenomonas ruminantium, while the straight rods clustered with Klebsiella species accessions in the databases. A partial 16S sequence strongly indicated that one of the isolates was Butyrivibrio fibrisolvens.