Roseicyclus sediminis sp. nov. and Roseicyclus salinarum sp. nov., isolated from marine environment, and reclassification of two species of the genus Roseibacterium as species of the genus Roseicyclus.

Abstract

Two Gram-stain-negative, facultatively anaerobic, rod-shaped bacteria were isolated from coastal sediments and salt marshes in Weihai, China, and designated as SDUM158017^T and SDUM158016^T, respectively. Both grew at temperatures ranging from 20 to 43°C and within a pH range of 6.0 to 9.0. However, strain SDUM158016^T grew in the presence of 1.0-7.0% (w/v) NaCl, whereas strain SDUM158017^T was able to grow in the presence of 1.0-10.0% (w/v) NaCl. Strains SDUM158016^T and SDUM158017^T contain major fatty acids of C_18 : 1 ω7ϲ and C_16 : 0 and contain Q10 as the sole quinone. Based on 16S rRNA gene sequence analysis, the closest relatives of strains SDUM158016^T and SDUM158017^T are 'Roseibacterium beibuensis' MCCC 1F00103^T, followed by Roseibacterium elongatum JCM 11220^T, with the highest similarities 97.1 and 97.3 %, respectively. The average nucleotide identity values between strain SDUM158016^T and species of the genera Roseibacterium and Roseicyclus ranged from 76.0 to 78.9 %, while they ranged from 75.9 to 78.6% for strain SDUM158017^T. These values are below the species delineation threshold of 98.6%, suggesting that both strains represent novel species. Phylogenetic analysis of the 16S rRNA genes and genome sequences further indicates that Roseibacterium species within the genus Roseicyclus and these isolates represent two potentially novel species within the genus Roseicyclus. Taken together, strains SDUM158017^T and SDUM158016^T represent two novel species of the genus Roseicyclus, for which the names Roseicyclus sediminis and Roseicyclus salinarum are proposed with the type strains SDUM158016^T (=KCTC 92632^T =MCCC 1H01367^T) and SDUM158017^T (=KCTC 92633^T =MCCC 1H01363^T), respectively. Based on phylogenetic and genomic analyses, we also propose the reclassification of Roseibacterium elongatum as Roseicyclus elongatus comb. nov. and Roseibacterium persicicum as Roseicyclus persicicus comb. nov.