Natronospirillum operosum gen. nov., sp. nov., a haloalkaliphilic satellite isolated from decaying biomass of a laboratory culture of cyanobacterium Geitlerinema sp. and proposal of Natronospirillaceae fam. nov., Saccharospirillaceae fam. nov. and Gynuellaceae fam. nov

A novel haloalkaliphilic bacterium, designated G-116T, was isolated from the decaying biomass of a laboratory culture of cyanobacterium Geitlerinema species. Cells of strain G-116T were Gram-stain-negative, motile spirilla. Strain G-116T showed high halotolerance to 20 % (w/v) NaCl (optimum growth at 3.5–6.0 %, w/v) and obligately alkaliphilic growth within the pH range 7.3–10.4 (optimum growth at pH 8.7–8.9). The major fatty acids identified were C16:0, summed feature 8 (C18:1 ω7c/C18 :1 ω6c), summed feature 3 (C16:1 ω7c/C16 :1 ω6c) and C19:0 cyclo ω8c. The polar lipids consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, an unidentified phospholipid, three unidentified amino lipids and five unidentified lipids. The predominant respiratory quinone was ubiquinone-8 (Q-8). The G+C content of the genomic DNA was 60.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the closest genus with a validly published name is a monotypic Salinispirillum and strain G-116T clustered with Salinispirillum marinum GCWy1T with a 16S rRNA gene sequence similarity of 94.3 %. Based on the data obtained from phenotypic and chemotaxonomic studies and the phylogenetic analysis, the isolate is proposed to be a representative of a novel genus and a novel species, Natronospirillum operosum gen. nov., sp. nov. Together with S. marinum they form a separate clade, for which a novel family, Natronospirillaceae fam. nov., is proposed. In addition, Saccharospirillaceae fam. nov. and Gynuellaceae fam. nov. are proposed to encompass the genera Saccharospirillum and Reinekea , and the genus Gynuella , respectively. All three novel families are within the order Oceanospirillales of the class Gammaproteobacteria . The type strain of the type species, Natronospirillum operosum gen. nov., sp. nov. is G-116T (=VKM B-3134T=KCTC 62956T).