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Abstract
An aerobic, moderately halophilic, Gram-negative, motile, non-sporulating rod-shaped bacterium, designated strain A10T, was isolated from the surface of leaves of the black mangrove Avicennia germinans and was subjected to a polyphasic taxonomic study. Strain A10T was able to grow at NaCl concentrations in the range 5–17.5 % (w/v) with optimum growth at 10 % (w/v) NaCl. Growth occurred at temperatures of 20–40 °C (optimal growth at 37 °C) and pH 5.5–8.5 (optimal growth at pH 7.0–8.0). The major respiratory quinone was ubiquinone 9. The major fatty acids were C16 : 0, C18 : 1 ω7c, C19 : 0 cyclo ω8c and C12 : 0 3-OH. The polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, and unidentified phospholipids, glycolipids and an aminoglycolipid. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strain A10T is closely related to Halomonas avicenniae MW2aT (95.7 % sequence similarity), Halomonas marisflavi SW32T (95.2 %) and Halomonas indalinina GC2.1T (95.0 %). Strain A10T formed a coherent phylogenetic branch with these three species, separated from other species of Halomonas and closely related genera (with 16S rRNA gene sequence similarities below 94.0 %). A complete 23S rRNA gene sequence comparison of strain A10T with closely related species confirmed the phylogenetic position of the novel isolate, forming a branch with the species Halomonas avicenniae, Halomonas indalinina and Halomonas marisflavi, separated from other species of the genera belonging to the family Halomonadaceae (showing sequence similarities below 91.7 %). DNA–DNA hybridization studies between strain A10T and Halomonas avicenniae MW2aT, Halomonas marisflavi DSM 15357T and Halomonas indalinina CG2.1T were 21, 17 and 10 %, respectively. These levels of DNA–DNA relatedness were low enough to classify strain A10T as representing a genotypically distinct species. Overall, the phenotypic, genotypic, chemotaxonomic and phylogenetic results demonstrated that strain A10T represents a new genus and species. The name Kushneria aurantia gen. nov., sp. nov. is proposed, with strain A10T (=CCM 7415T=CECT 7220T) as the type strain. This is the type species of the new proposed genus, which belongs to the family Halomonadaceae. In addition, our data support the placement of the species Halomonas marisflavi, Halomonas indalinina and Halomonas avicenniae within this new genus, as Kushneria marisflavi comb. nov., Kushneria indalinina comb. nov. and Kushneria avicenniae comb. nov., respectively.
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