Butyrivibrio hungatei sp nov and Pseudobutyrivibrio xylanivorans sp nov., butyrate-producing bacteria from the rumen

Two novel Gram-negative, anaerobic, non-spore-forming, butyrate-producing bacterial species, strains Mz 5(T) and X 615(T), were isolated from the rumen fluid of cow and sheep. Both strains were curved rods that were motile by means of single polar or subpolar flagellum and common in the rumen microbial ecosystem. Strain Mz 5(T) produced high xylanase, proteinase, pectin hydrolase and DNase activities; 1,4-beta-endoglucanase was also detected in the culture medium. The bacterium utilized a wide range of carbohydrates. Glucose was fermented to formate, butyrate, lactate, succinate and ethanol. The DNA G + C content was 42-1 mol%. The complete 16S rDNA sequence was obtained and phylogenetic relationships were determined. Strain MZ 5(T) and related isolates were located in clostridial cluster XIVa and were closely related to Pseudobutyrivibrio ruminis, Butyrivibrio crossotus, Roseburia cecicola and Eubacterium rectale. The name proposed for this novel bacterium is Pseudobutyrivibrio xylanivorans; the type strain is Mz 5(T) (= DSM 14809(T) = ATCC BAA-455(T)). Strain X 615(T) produced no fibrolytic activity, but utilized a wide range of carbohydrates. Glucose was fermented to formate, acetate, butyrate and ethanol. The DNA G + C content was 44-8 mol%. The complete 16S rDNA sequence was obtained and phylogenetic relationships were determined. Strain X 615(T) was located in clostridial cluster XIVa and was closely related to Clostridium proteoclasticum, Butyrivibrio fibrisolvens and Eubacterium, halii. The name proposed for this novel bacterium is Butyrivibrio hungatei; the type strain is X 615(T) (=DSM 14810(T) =ATCC BAA-456(T)).