Sulfurifustis variabilis gen. nov., sp. nov., a sulfur oxidizer isolated from a lake, and proposal of Acidiferrobacteraceae fam. nov. and Acidiferrobacterales ord. nov. A novel autotrophic bacterium, strain skN76 T , was isolated from sediment of a lake in Japan. As sole electron donor to support chemolithoautotrophic growth, the strain oxidized thiosulfate, tetrathionate and elemental sulfur. For growth, the optimum temperature was 42-45 8C and the optimum pH was 6.8-8.2. The cells were Gram-stain-negative, catalase-positive and oxidasepositive. The strain exhibited changes in morphology depending on growth temperature. Cells grown at the optimum temperature were rod-shaped (0.9-3.0 mm long and 0.3-0.5 mm wide), whereas a filamentous form was observed when the strain was cultured at the lowest permissive growth temperatures. The G+C content of genomic DNA was 69 mol%. The major components in the fatty acid profile were C 16 : 0 , summed feature 3 (C 16 : 1 v7c and/or C 16 : 1 v6c) and summed feature 9 (iso-C 17 : 1 v9c and/or 10-methyl C 16 : 0 ). Phylogenetic analysis based on 16S rRNA gene sequences indicated that the closest cultivated relative of strain skN76 T was Acidiferrobacter thiooxydans m-1 T , with sequence similarity of 93 %. On the basis of its phylogenetic and phenotypic properties, strain skN76 T (5DSM 100313 T 5 NBRC 110942 T ) is proposed as the type strain of a novel species of a novel genus, Sulfurifustis variabilis gen. nov., sp. nov. Novel taxa, Acidiferrobacteraceae fam. nov. and Acidiferrobacterales ord. nov., are also proposed to accommodate the genera Acidiferrobacter and Sulfurifustis gen. nov.

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A novel sulfur oxidizer, strain wk12 T , was isolated from an industrially synthesized lead (II) sulfide. The G+C content of the genomic DNA was around 58.5 mol%. The major components in the cellular fatty acid profile were summed feature 3 (C 16 : 1 v7c and/or C 16 : 1 v6c), C 16 : 0 and summed feature 8 (C 18 : 1 v7c and/or C 18 : 1 v6c). The strain oxidized lead sulfide, thiosulfate and tetrathionate as electron donors to support autotrophic growth. Cells of strain wk12 T were motile, rod-shaped (0.5-1.060.7-2.2 mm), and Gram-stain-negative. For growth, the temperature range was 5-37 8C, and optimum growth was observed at 28-32 8C. The pH range for growth was 5.8-8.7, with optimum growth at pH 6.4-7.1. Optimum growth of the isolate was observed in medium without NaCl, and no growth was observed in the medium containing 0.5 M or more NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate belongs to the class Acidithiobacillia. The closest relative with a validly published name was Thermithiobacillus tepidarius DSM 3134 T , with a 16S rRNA gene sequence similarity of 96 %. On the basis of phylogenetic and phenotypic properties, strain wk12 T represents a novel species of the genus Thermithiobacillus, for which the name Thermithiobacillus plumbiphilus sp. nov. is proposed. The type strain is wk12 T (5NBRC 111508 T 5DSM 101799 T ).

A novel sulfur-oxidizing bacterium, designated strain BiS0 T , was isolated from a sediment sample collected from a freshwater lake in Japan. The cells were rod-shaped, 1.