Fibrolytic Bacterium Isolated From Buffalo Rumen Phylogenetically Closely Related to Butyrivibrios and Pseudobutyrivibrios

Abstract

Butyrivibrios and Pseudobutyrivibrios represent a significant proportion of ruminal bacteria and large culturable Butyrivibrio strains that contribute to fiber degradation and the utilization of various substrates. Butyrivibrio and Pseudobutyrivibrio are highly adaptable to ruminal conditions and play an important role in fiber fermentation. This study isolated the high potential fibrolytic and non-fibrolytic bacteria Butyrivibrio and Pseudobutyrivibrio from buffalo rumen and studied synergism between fibrolytic and non-fibrolytic bacteria in co-culture. Two mature, rumen-fistulated swamp buffaloes were fed roughage of either rice straw or rice straw plus concentrate. Roughage suspended in the rumen was used as the source of isolates. Six hours after feeding, roughage from the rumen was serially diluted and used for pure culture isolation by the roll tube technique under anaerobic conditions. Fiber degrading and cellobiose utilizing bacteria were collected and screened for further characterization, consisting of Gram-staining, 16S rDNA sequencing, utilization of different carbon sources, digestibility on fiber powders, intracellular fibrolytic enzyme activities, volatile fatty acid production and co-culture digestibility between fibrolytic Butyrivibrio and non-fibrolytic bacteria. A total of 165 Gram-negative fibrolytic bacteria were obtained from 1,125 colonies and then 21 fibrolytic and 20 non-fibrolytic strains were selected that could utilize cellobiose efficiently. Fibrolytic bacteria were identified as 10 strains of Butyrivibrio sp. and 4 strains of Pseudobutyrivibrio spp. and non-fibrolytic bacteria were identified as 4 strains of Butyrivibrio sp. and 3 strains of Pseudobutyrivibrio spp. Isolates of fibrolytic Butyrivibrios sp. and Pseudobutyrivibrios spp., especially B. fibrisolvens KU-F83, showed high digestibility of fiber powder and high intracellular fibrolytic enzyme activity. Co-culture of fibrolytic B. fibrisolvens KU-F83 and non-fibrolytic Butyrivibrios, Pseudobutyrivibrios and S. ruminantium S137 could ehance rice straw digestibility and the propionate portion while reducing cellulose digestibility.