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Two Gram-reaction-negative, yellow-orange-pigmented, rod-shaped bacterial strains, designated YC6722(T) and YC6723(T), were isolated from rhizosphere soil samples collected from rice fields in Jinju, Korea. Strains YC6722(T) and YC6723(T) grew optimally at 25-30 °C and at pH 7.0-8.5. Phylogenetic analyses of 16S rRNA gene sequences showed that strain YC6722(T) was most closely related to Sphingomonas jaspsi TDMA-16(T) (96.6 % sequence similarity) and strain YC6723(T) was related most closely to Sphingomonas aquatilis JSS7(T) (96.9 %). The two strains contained ubiquinone-10 (Q-10) as the major respiratory quinone system and sym-homospermidine as the major polyamine. The G+C contents of the genomic DNA of strains YC6722(T) and YC6723(T) were 63.3 and 61.0 mol%, respectively. The major fatty acid was C(18 : 1)ω7c. The polar lipids detected in the two strains were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, sphingoglycolipid, phosphatidyldimethylethanolamine and other unknown lipids. On the basis of their phylogenetic positions, and their biochemical and phenotypic characteristics, strains YC6722(T) and YC6723(T) represent two novel species of the genus Sphingomonas, for which the names Sphingomonas oryziterrae sp. nov. ( = KCTC 22476(T)  = DSM 21455(T)) and Sphingomonas jinjuensis sp. nov. (KCTC 22477(T)  = DSM 21457(T)) are proposed.

A novel bacterium (strain K4(T)) belonging to the genus Sphingomonas was isolated from tidal flat sediment in Korea. Its morphology, physiology, biochemical features and 16S rRNA gene sequence were characterized. Colonies of this strain are yellow in colour and the cells are rod-shaped, exhibiting negative Gram staining. The strain grows at 0-5 % (w/v) NaCl and 20-35 degrees C, with optimal growth occurring at 0 % (w/v) NaCl and 30 degrees C. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain K4(T) is associated with the genus Sphingomonas. Within the phylogenetic tree, this novel strain shares a branching point with Sphingomonas asaccharolytica Y-345(T), with which it shares 97.3 % 16S rRNA gene sequence similarity. The polyamine pattern predominantly contains the Sphingomonas-specific triamine sym-homospermidine. Combined analysis of 16S rRNA gene sequences, DNA-DNA relatedness, physiological and biochemical test results identified genotypic and phenotypic differences between strain K4(T) and other Sphingomonas species. On the basis of these differentiating features, it is concluded that strain K4(T) (=KCTC 22050(T)=DSM 19475(T)) represents a novel species of the genus Sphingomonas, for which the name Sphingomonas aestuarii sp. nov. is proposed.