Halomicroarcula pellucida gen. nov., sp nov., a non-pigmented, transparent-colony-forming, halophilic archaeon isolated from solar salt

A novel halophilic strain, BNERC31(T), was isolated from solar salt, 'Sel marin de Guerande', imported from France. Colonies on agar medium containing soluble starch, sodium citrate, sodium glutamate and inorganic salts were non-pigmented and transparent, while cells obtained by centrifuging liquid cultures were red-pigmented. Cells of strain BNERC31(T) were non-motile, pleomorphic, stained Gram-negative and lysed in distilled water. Growth occurred with 20-30 % (w/v) NaCl (optimum, 25%, w/v), with 0-500 mM MgCl2 (optimum, 10 mM), at pH 6.0-8.5 (optimum, pH 7.0) and at 25-55 degrees C (optimum, 40 degrees C). Growth was dependent on soluble starch, and inhibited completely by 0.50% organic nutrients, such as Casamino acids or yeast extract. The DNA G+C content was 64.1 mol%. Strain BNERC31(T) possessed at least two heterogeneous 16S rRNA genes, and the sequence of the orthologous gene (preceded by the dihydroorotate oxidase gene, pyrD) showed the highest similarity (96.5%) to that of Haloarcula marismortui JCM 8966(T). The RNA polymerase subunit B' gene sequence showed the highest similarity (91.7%) to that of Haloarcula amylolytica JCM 13557(T). The polar lipids of strain BNERC31(T) were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate, diglycosyl diether and sulfated diglycosyl diether, similar to those of species of the genus Halomicrobium. The phenotypic and phylogenetic characteristics showed that strain BNERC31(T) differed from species of the genera Haloarcula and Halomicrobium and indicated that it represents a novel species in a new genus, for which the name Halomicroarcula pellucida gen. nov., sp. nov. is proposed. The type strain of the type species is BNERC31(T) (=JCM 17820(T)=CECT 7537(T)).