Thiomicrorhabdus immobilis sp. nov., a mesophilic sulfur-oxidizing bacterium isolated from sediment of a brackish lake in northern Japan

A novel sulfur-oxidizing bacterium, strain Am19(T), was isolated from sediment of a brackish lake. Strain Am19(T) grew chemolithoautotrophically on inorganic sulfur compounds, and heterotrophic growth was not observed. Cells were rod-shaped with length of 1.1-3.0 mu m and diameter of 0.5-0.8 mu m. Growth was observed at 5-37 degrees C with an optimum growth temperature of 30 degrees C. The pH range for growth was 5.6-8.5 with an optimum pH of 6.6-7.0. Major fatty acids were summed feature 3 (C-16: 1 omega 7c and/or C-16: 1 omega 6c), summed feature 8 (C-18: 1 omega 7c and/or C-18: 1 omega 6c) and C-16: 0. The sole respiratory quinone was ubiquinone-8. The complete genome of strain Am19(T) is composed of a circular chromosome with length of 2.5 Mbp and G + C content of 42.7 mol%. Phylogenetic analysis based on genomic data indicated that strain Am19(T) belongs to the genus Thiomicrorhabdus but is distinct from any existing species. Analysis of the 16S rRNA gene supported creation of a new species to accommodate strain Am19(T). On the basis of genomic and phenotypic characteristics, strain Am19(T) (= NBRC 114602( T) = BCRC 81336( T)) is proposed as the type strain of a new species, with name of Thiomicrorhabdus immobilis sp. nov.