Ectothiorhodospira abdelmalekii sp. nov., a New Halophilic and Alkaliphilic Phototrophic Bacterium

A new species of the genus Ectothiorhodospira is described isolated from alkaline soda lakes of the Wadi Natrun in Egypt. In most of its properties it resembles the recently described Ectothiorhodospira halochloris, which had been isolated from similar lakes of the same area. The new species, Ectothiorhodospira abdelmalekii, has spiral-shaped cells with 0.9-1.2 μm diameter, it is polarly flagellated with sheated flagella, has lamellar photosynthetic membrane stacks, possesses bacteriochlorophyll b as the main photosynthetic pigment, and has a DNA base composition of 63.3–63.8 mol% G + C. Photolithotrophic growth with sulfide or elemental sulfur as electron donors is the predominant mode of life. During sulfide oxidation to sulfate, elemental sulfur is accumulated outside the cells. Acetate, pyruvate, fumarate and succinate are photoassimilated. The properties of E. halochloris and E. abdelmalekii are compared.