Halobacterium pharaonis sp. nov., a New, Extremely Haloalkaliphilic Archaebacterium with Low Magnesium Requirement

Abstract

Halobacterium pharaonis sp. nov. was isolated from the alkaline brines of eutrophic desert lakes of Wadi Natrun, Egypt. The new species differs from the Halobacterium species so far described in being alkaliphilic, in its extremely low Mg²⁺ requirement for growth, and in its DNA base composition (64.3 mol% guanine + cytosine, determined by thermal decomposition; no satellite DNA). Magnesium in concentrations above 0.01 mol/1 (≈ 0.25% w/v MgSO₄·7H²O) inhibits growth. Good growth occurs between pH 7.7 and 9.3, optimal growth at pH 8.5.