Isolation and characterization of glycerol-fermenting bacteria from the rumen of red deer

Abstract

The rumen contents of juvenile red deer (Cervus elaphus) were used as a source for the enrichment of obligately anaerobic glycerol-fermenting bacteria. Three bacterial strains were isolated from the 10−4 dilution (isolates DR6A and DR6B) and 10−9 dilution (isolate DR7) of the deer rumen contents. The isolates DR6A, DR6B, and DR7 produced ethanol (42 mM) and acetate (5 mM), propionate (31 mM) and acetate (42 mM), and formate (25 mM) and ethanol (38 mM), respectively, as the major glycerol fermentation products. Interestingly, acetate, propionate, and formate were observed to be the major glycerol fermentation products in mixed cultures obtained from the deer rumen. The three isolates were all shown to be related phylogenetically to the ruminal species Clostridium clostridiiforme, Clostridium celerecrescens, and Clostridium aerotolerans within the clostridial taxonomic cluster XIVa, on the basis of 16S rRNA gene sequence comparisons. But, because of phenotypic differences, each isolate is considered to be a new species within the genus Clostridium, which has not been previously described or isolated from the rumen ecosystem.Key words: red deer, ecology, glycerol fermentation, Clostridium, rumen, 16S rRNA.