Haloferax

Abstract

Ha.lo.fe' rax . Gr. n. hals, halos salt; L. neut. adj. ferax fertile; M.L. neut. n. Haloferax salt (requiring) and fertile. Euryarchaeota / Halobacteria / Haloferacales / Haloferacaceae / Haloferax Cells extremely pleomorphic, most commonly flattened disks or cups (1–3 × 2–3 µm). Resting stages are not known. Gram negative. Nonmotile or motile; motility often difficult to observe . One species is gas vacuolate. Colonies have a mucoid appearance. Strictly aerobic. Nitrate can be reduced under anaerobic conditions. Oxidase and catalase positive. Extremely halophilic, with growth occurring in media containing 1.5–4.5 M NaCl ; optimum concentration: 2.5 M NaCl. Temperature range for growth: 30–55°C; optimum temperature: ~35°C. pH range for growth: 5–8; optimum pH: 7. Minimal Mg 2+ requirement for growth: 0.01–0.04 M. Chemoorganotrophic, utilizing many substrates as sources of carbon and energy. Acid is produced from sugars. Amino acids are not required. Polyhydroxyalkanoates are accumulated under certain conditions. The polar lipids are characterized by the presence of C 20 C 20 derivatives of S‐DGD‐1 and the absence of PGS . The mol % G + C of the DNA is : 59.1–65.5. A minor DNA component may be present. Type species : Haloferax volcanii (Mullakhanbhai and Larsen 1 9 7 5) Torreblanca, Rodriguez‐Valera, Juez, Ventosa, Kamekura and Kates 1986b, 573 (Effective publication: Torreblanca, Rodriguez‐Valera, Juez, Ventosa, Kamekura and Kates 1986a, 98) ( Halobacterium volcanii Mullakhanbhai and Larsen 1975, 213.)