Syntrophomonas zehnderi sp. nov., an anaerobe that degrades long-chain fatty acids in co-culture with Methanobacterium formicicum

摘要

An anaerobic, mesophilic, syntrophic fatty-acid-oxidizing bacterium, designated strain OL-4T, was isolated as a co-culture with Methanobacterium formicicum DSM 1535NT from an anaerobic expanded granular sludge bed reactor used to treat an oleate-based effluent. Strain OL-4T degraded oleate, a mono-unsaturated fatty acid, and straight-chain fatty acids C4 : 0–C18 : 0 insyntrophic association with Methanobacterium formicicum DSM 1535NT. Even-numbered fatty acids were degraded to acetate and methane whereas odd-numbered fatty acids were degraded to acetate, propionate and methane. Branched-chain fatty acids were not degraded. The bacteriumcould not grow axenically with any other substrate tested and therefore is considered to be obligately syntrophic. Fumarate, sulfate, thiosulfate, sulfur and nitrate could not serve as electron acceptors for strain OL-4T to degrade oleate or butyrate. Cells of strain OL-4T were curved rods, formed spores and showed a variable response to Gram staining. Phylogenetic analysis basedon 16S rRNA gene sequences revealed that strain OL-4T was most closely related to thefatty-acid-oxidizing, syntrophic bacterium Syntrophomonas sp. TB-6 (95% similarity),Syntrophomonas wolfei subsp. wolfei DSM 2245T (94% similarity) and Syntrophomonaserecta DSM 16215T (93% similarity). In addition to this moderate similarity, phenotypic and physiological characteristics, such as obligate syntrophy, spore formation and utilization of a broader substrate range, differentiated strain OL-4T from these Syntrophomonas species.Therefore strain OL-4T represents a novel species, for which the name yntrophomonas zehnderi sp. nov. is proposed. The type strain is OL-4T (=DSM 17840T=JCM 13948T).