Thauera humireducens sp. nov., a humus-reducing bacterium isolated from a microbial fuel cell

A Gram-negative, rod-shaped, non-spore-forming bacterium, designated SgZ-1(T), was isolated from the anode biofilm of a microbial fuel cell. The strain had the ability to grow under anaerobic condition via the oxidation of various organic compounds coupled to the reduction of anthraquione-2,6-disulfonate (AQDS) to anthrahydroquinone-2,6-disulfonate (AHQDS). Growth occurred in TSB in the presence of 0-5.5 % (w/v) NaCl (optimum 0-1 %), at 10-45 °C (optimum 25-37 °C) and at pH 6.0-10.0 (optimum 8.0-8.5). Based on 16S rRNA gene sequence similarity, strain SgZ-1(T) belonged to the genus Thauera. The highest level of 16S rRNA gene sequences similarity (96.7 %) was found to be with Thauera aminoaromatica S2(T) and Thauera selenatis AX(T), and lower values were obtained when compared with other recognized Thauera species. Chemotaxonomic analysis revealed that strain SgZ-1(T) contained Q-8 as the predominant quinone, and putrescine and 2-hydroxyputrescine as the major polyamines. The major cellular fatty acids (>5 %) were C16 : 1ω6c and/or C16 : 1ω7c (44.6 %), C16 : 0 (18.8 %), and C18 : 1ω6c and/or C18 : 1ω7c (12.7 %). Based on its phenotypic and phylogenetic properties, chemotaxonomic analysis and the results of physiological and biochemical tests, strain SgZ-1(T) ( = KACC 16524(T) = CCTCC M 2011497(T)) was designated the type strain of a novel species of the genus Thauera, for which the name Thauera humireducens sp. nov. was proposed.