Syntrophomonas palmitatica sp. nov., an anaerobic, syntrophic, long-chain fatty-acid-oxidizing bacterium isolated from methanogenic sludge.

A mesophilic, syntrophic, fatty-acid-oxidizing anaerobic strain, designated MPA(T), was isolated from granular sludge in a mesophilic upflow anaerobic sludge blanket reactor used to treat palm oil mill effluent. Cells were slightly curved, non-motile rods. Spore formation was not observed. The optimal temperature for growth was around 37 degrees C and optimal pH for growth was 7.0. Strain MPA(T) was able to grow on crotonate or pentenoate plus butyrate in pure culture. In co-culture with the hydrogenotrophic methanogen Methanospirillum hungatei, strain MPA(T) was able to oxidize straight-chain saturated fatty acids with carbon chain lengths of C4-C18. The strain was unable to utilize sulfate, sulfite, thiosulfate, nitrate, fumarate, iron(III) or DMSO as an electron acceptor. The G+C content of the DNA was 45.0 mol%. Based on comparative 16S rRNA gene sequence analysis, strain MPA(T) was found to be a member of the genus Syntrophomonas and was most closely related to the type strains of Syntrophomonas curvata and Syntrophomonas sapovorans (sequence similarities of 94 %). Genetic and phenotypic characteristics demonstrated that strain MPA(T) represents a novel species, for which the name Syntrophomonas palmitatica sp. nov. is proposed. The type strain is MPA(T) (=JCM 14374(T)=NBRC 102128(T)=DSM 18709(T)).