Tepidibacillus decaturensis sp. nov., a microaerophilic, moderately thermophilic iron-reducing bacterium isolated from 1.7 km depth groundwater

A Gram-stain-negative, microaerophilic rod-shaped organism designated as strain Z9^T was isolated from groundwater of 1.7 km depth from the Mt. Simon Sandstone of the Illinois Basin, Illinois, USA. Cells of strain Z9^T were rod shaped with dimensions of 0.3×(1–10) μm and stained Gram-negative. Strain Z9^T grew within the temperature range 20–60 °C (optimum at 30–40 °C), between pH 5 and 8 (optimum 5.2–5.8) and under salt concentrations of 1–5% (w/v) NaCl (optimum 2.5% NaCl). In addition to growth by fermentation and nitrate reduction, this strain was able to reduce Fe(III), Mn(IV), Co(III) and Cr(VI) when H₂ or organic carbon was available as the electron donor, but did not actively reduce oxidized sulfur compounds (e.g. sulfate, thiosulfate or S⁰). The G+C content of the DNA from strain Z9^T was 36.1 mol%. Phylogenetic analysis of the 16S rRNA gene from strain Z9^T showed that it belongs to the class Bacilli and shares 97% sequence similarity with the only currently characterized member of the genus Tepidibacillus, T. fermentans. Based on the physiological distinctness and phylogenetic information, strain Z9^T represents a novel species within the genus Tepidibacillus, for which the name Tepidibacillus decaturensis sp. nov. is proposed. The type strain is Z9^T (=ATCC BAA-2644^T=DSM 103037^T).