Diversity of alkaliphilic halobacteria: proposals for transfer of Natronobacterium vacuolatum, Natronobacterium magadii, and Natronobacterium pharaonis to Halorubrum, Natrialba, and Natronomonas gen. nov., respectively, as Halorubrum vacuolatum comb. nov., Natrialba magadii comb. nov., and Natronomonas pharaonis comb. nov., respectively

Abstract

The 16S rRNA genes of three species of the genus Natronobacterium (Natronobacterium gregoryi, Natronobacterium pharaonis, and Natronobacterium vacuolatum) were sequenced and compared to that of the previously sequenced species Natronobacterium magadii. The sequences revealed that Natronobacterium pharaonis was phylogenetically distinct from the other members of the genus and also from other recognized genera of the family Halobacteriaceae. However, Natronobacterium vacuolatum and Natronobacterium magadii were found to be most closely related to the genera Halorubrum and Natrialba, respectively. An unidentified haloalkaliphile, strain SSL1, was also closely related to Natronobacterium magadii and Natrialba asiatica. On the basis of phylogenetic tree reconstructions, signature bases specific for individual genera, and sequences of spacer regions between 16 and 23S rRNA genes, we propose the following changes: Natronobacterium pharaonis to be transferred to Natronomonas gen. nov. as Natronomonas pharaonis gen. nov., comb. nov.; Natronobacterium vacuolatum to be transferred to the genus Halorubrum as Halorubrum vacuolatum comb. nov.; and Natronobacterium magadii to be transferred to the genus Natrialba as Natrialba magadii.