Two bacterial isolates, designated AF-51^T and AF-50, with an optimum growth temperature of about 45 °C and an optimum pH for growth between 6.0 and 6.5, were recovered from a hot spring in the Furnas, Área da Fonte 1825, on the Island of São Miguel in the Azores. Based on 16S rRNA gene sequence analysis, these strains were related most closely to the type strain of Hydrotalea flava at a pairwise similarity of 95.7 %. The two strains were orange-pigmented and formed non-motile, rod-shaped cells that stained Gram-negative and were aerobic and oxidase- and catalase-positive. The major fatty acids were iso-C_{15 : 0}, iso-C_{17 : 0} 3-OH and iso-C_{16 : 0}. The major respiratory quinone was menaquinone 7. Based on phylogenetic, physiological and biochemical characteristics, these strains from the Azores are considered to represent a single novel species of the genus Hydrotalea , for which the name Hydrotalea sandarakina sp. nov. is proposed. The type strain is AF-51^T ( = DSM 23241^T = LMG 25526^T). We provide emended descriptions of the genus Hydrotalea and of H. flava to reflect new results obtained in this study.