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

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} <i>ω</i>7<i>ϲ</i> 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 '<i>Roseibacterium beibuensis</i>' MCCC 1F00103^T, followed by <i>Roseibacterium elongatum</i> 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 <i>Roseibacterium</i> and <i>Roseicyclus</i> 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 <i>Roseibacterium</i> species within the genus <i>Roseicyclus</i> and these isolates represent two potentially novel species within the genus <i>Roseicyclus</i>. Taken together, strains SDUM158017^T and SDUM158016^T represent two novel species of the genus <i>Roseicyclus</i>, for which the names <i>Roseicyclus sediminis</i> and <i>Roseicyclus salinarum</i> 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 <i>Roseibacterium elongatum</i> as <i>Roseicyclus elongatus</i> comb. nov. and <i>Roseibacterium persicicum</i> as <i>Roseicyclus persicicus</i> comb. nov.