| Summary: | Strain MS-P2<sup>T</sup> was isolated from microbial mats associated with Mushroom Spring, an alkaline siliceous hot spring in Yellowstone National Park, WY, USA. The isolate grows chemoheterotrophically by oxygen-dependent respiration, and light stimulates photoheterotrophic growth under strictly oxic conditions. Strain MS-P2<sup>T</sup> synthesizes bacteriochlorophyll <i>a</i> and the carotenoid spirilloxanthin. However, photoautotrophic growth did not occur under oxic or anoxic conditions, suggesting that this strain should be classified as an aerobic anoxygenic phototrophic bacterium. Strain MS-P2<sup>T</sup> cells are motile, curved rods about 0.5 to 1.0 μm wide and 1.0 to 1.5 μm long. The optimum growth temperature is 45–50 °C, and the optimum pH for growth is circum-neutral (pH 7.0–7.5). Sequence analysis of the 16S rRNA gene revealed that strain MS-P2<sup>T</sup> is closely related to <i>Elioraea</i> species, members of the class <i>Alphaproteobacteria</i>, with a sequence identity of 96.58 to 98%. The genome of strain MS-P2<sup>T</sup> is a single circular DNA molecule of 3,367,643 bp with a mol% guanine-plus-cytosine content of 70.6%. Based on phylogenetic, physiological, biochemical, and genomic characteristics, we propose this bacteriochlorophyll <i>a</i>-containing isolate is a new species belonging to the genus <i>Elioraea</i>, with the suggested name <i>Elioraea</i><i>tepida</i>. The type-strain is strain MS-P2<sup>T</sup> (= JCM33060<sup>T</sup> = ATCC TSD-174<sup>T</sup>).
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