Halonotius pteroides gen. nov., sp. nov., an extremely halophilic archaeon recovered from a saltern crystallizer

Strains 1.15.5(T), 2.27.5, 5.24.4 and 6.14.5 were isolated from a solar saltern. They have flattened, rod-shaped cells and are aerobic, extremely halophilic members of the domain Archaea and family Halobacteriaceae. Cells stained Gram-negative and grew optimally in media around neutral pH and containing 20-24 % (w/v) (strains 1.15.5(T) and 2.27.5) or 22-24 % (w/v) (5.24.4 and 6.14.5) salts. Mg(2+) was not required. The DNA G+C contents of these isolates were all close to 58 mol%, and DNA-DNA cross-hybridization showed a mean relatedness of 77 %. Their 16S rRNA gene sequences differed by no more than 1.6 % from each other. Phylogenetic tree reconstructions with other recognized members of the Halobacteriaceae indicated that they formed a distinct clade, with the closest relative being Halorubrum saccharovorum (86.6-87.6 % 16S rRNA gene sequence similarity to the type strain). The only major polar lipid of all four isolates was the sulfated diglycosyl diether lipid S-DGD-1. By phase-contrast microscopy, the long, flattened cells of these strains often displayed a 'wing-like' shape. The phenotypic and phylogenetic data support the placement of these isolates into a novel species in a new genus within the Halobacteriaceae, for which we propose the name Halonotius pteroides gen. nov., sp. nov. The type strain of Halonotius pteroides is 1.15.5(T) (=JCM 14355(T) =CECT 7525(T) =DSM 18729(T)), with the additional reference strains 2.27.5 (=JCM 14356 =DSM 18671), 5.24.4 (=JCM 14357 =DSM 18673) and 6.14.5 (=JCM 14358 =DSM 18692).