Isolation and characterization of novel sulphate-reducing Fusobacterium sp. and their effects on in vitro methane emission and digestion of wheat straw by rumen fluid from Indian riverine buffaloes

Seven isolates of sulphate-reducing bacteria were isolated from the rumen of buffalo and characterized morphologically, physiologically and phylogenically. A PCR assay and sequencing confirmed that all sulphate reducing isolates possessed the dissimilatory sulphite reductase gene. Sequencing of 16S ribosomal DNA indicated that the SRB isolates were highly homologous with Fusobacterium genus. The novel SRB isolates were evaluated for their suitability to reduce CH4 production and stimulate fibre digestion in vitro. When added to rumen fluid from buffalo, most isolates decreased (P<0.05) CH4 (mL/L) concentration, increased propionate production, but did not alter H2S production. The isolate SRBBR 5 had the highest decrease in CH4 emission compared to control, reducing it from 2.66 to 1.64 mmol CH4/g DM truly digested after 72 h of fermentation. Addition of SRBBR5 also increased (P<0.05) fibre digestion (15% in apparent digestibility and 40% in true digestibility), xylanase activity and numbers of cellulolytic bacteria in the incubation fluid with no change in the numbers of methanogens or fungi. Results show that SRBBR5 has potential as a microbial feed additive to reduce CH4 emissions and improve fibre digestibility in ruminants. rticle is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.