Halomonas rifensis sp. nov., an exopolysaccharide-producing, halophilic bacterium isolated from a solar saltern

Abstract

A polyphasic taxonomic study was conducted on strain HK31T, a moderately halophilic bacterium isolated from a solar saltern in Chefchaouen, Morocco. The strain was a Gram-reaction-negative, oxidase-positive rod, which was motile by means of peritrichous flagella. The strain required NaCl for growth and grew in salt concentrations (mixture of sea salts) of 0.5–20 % (w/v) (optimum 5–7.5 %, w/v), at 25–45 °C (optimum 32 °C) and at pH 5–10 (optimum pH 6–9). Strain HK31T did not produce acids from sugars and its metabolism was respiratory, using oxygen as terminal electron acceptor. The strain was positive for the accumulation of poly-β-hydroxyalkanoate granules and formed mucoid colonies due to the excretion of an exopolysaccharide. The DNA G+C content was 61.5 mol%. 16S rRNA gene sequence analysis indicated that it belonged to the genus Halomonas in the class Gammaproteobacteria. The most phylogenetically related species was Halomonas anticariensis, with which strain HK31T showed a 16S rRNA gene sequence similarity of 96.48 %. Its major fatty acids were C18 : 1ω7c, C16 : 0, C19 : 0 cyclo ω8c , C16 : 1ω7c/iso-C15 : 0 2-OH and C12 : 0 3-OH and the predominant respiratory lipoquinone was ubiquinone with nine isoprene units (Q-9). Based on the evidence provided in this study, strain HK31T ( = CECT 7698T  = LMG 25695T) represents a novel species of the genus Halomonas, for which the name Halomonas rifensis is proposed.