Alkalispirillum mobile gen. nov., spec. nov., an alkaliphilic non-phototrophic member of the Ectothiorhodospiraceae

Abstract.

From cultures of the anoxygenic phototroph Halorhodospira halophila SL-1, an aerobic, gram-negative spirillum was isolated. This moderately halophilic, alkaliphilic bacterium was motile by means of a single polar flagellum. It is described here as Alkalispirillum mobile gen. nov., spec. nov. Phylogenetic analysis of the Alkalispirillum mobile 16S rRNA gene led to its classification in the γ-subclass of the Proteobacteria, as it appears closely related to phototrophic purple sulfur bacteria of the genera Ectothiorhodospira and Halorhodospira. Surprisingly, A. mobile is an obligate aerobe. The organism grows optimally with a number of carboxylic acids (such as sodium acetate) as carbon source, at 2% (i.e. approximately 0.34 M) sodium chloride, at pH 9–10, and at temperatures ranging from 35 to 38 °C. The dominant cellular fatty acids of Alkalispirillum mobile are C_12:0, C_16:0, C_{18:1 cis 11}, and C_18:0; its G+C content is 66.2±0.5 mol%.