Syntrophaceticus schinkii gen. nov., sp. nov., an anaerobic, syntrophic acetate-oxidizing bacterium isolated from a mesophilic anaerobic filter

A mesophilic, syntrophic acetate-oxidizing bacterium, designated strain Sp3T, was isolated from sludge from a mesophilic methanogenic digestor operating at a high ammonium concentration (6.4 g L⁻¹ NH₄⁺-N). The strain showed acetate-oxidizing ability in cocultivation with a hydrogen-consuming methanogen. Comparative 16S rRNA gene sequence analysis confirmed that strain Sp3T belonged to the Firmicutes-Clostridia class. The most closely related species was Thermacetogenium phaeum (16S rRNA gene sequence identity 92%). Strain Sp3T used ethanol, betaine and lactate as carbon and electron sources and showed growth between 25 and 40 °C and pH 6.0 and 8.0. Based on the phylogenetic position and the physiological characteristics of strain Sp3T, this new syntrophic, acetate-oxidizing bacterium is proposed as the new genus and species Syntrophaceticus schinkii, with Sp3T (=JCM 16669T) as the type strain. An isolate (strain Esp=JCM 16670) with high 16S rRNA gene sequence identity (99%) to syntrophic acetate-oxidizing Clostridium ultunense was also retrieved from the methanogenic digestor.