Cyclobacterium xiamenense sp. nov., isolated from aggregates of Chlorella autotrophica, and emended description of the genus Cyclobacterium.

A novel Gram-stain-negative, horseshoe-shaped, non-motile bacterium, designated strain KD51(T), forming colonies coloured pink by carotenoid pigments, was isolated from aggregates of the alga Chlorella autotrophica collected from the coastal sea off the city of Xiamen, Fujian Province, China. 16S rRNA gene sequence comparison showed that strain KD51(T) was a member of the genus Cyclobacterium, forming a distinct lineage with Cyclobacterium lianum HY9(T). The 16S rRNA gene sequence similarity between strain KD51(T) and the type strains of species of the genus Cyclobacterium ranged from 92.1 % to 95.2 %. Growth occurred at 4-40 °C (optimum, 28 °C), in the presence of 3-9 % NaCl (optimum, 3-5 %) and at pH 6-10 (optimum, pH 7.5). The dominant fatty acids (>20 %) of strain KD51(T) were iso-C15 : 0 (32.2 %) and summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c; 22.2 %). The DNA G+C content was 41.7 mol% and the only respiratory quinone was menaquinone-7. On the basis of phenotypic data and phylogenetic inference, strain KD51(T) represents a novel species of the genus Cyclobacterium, for which the name Cyclobacterium xiamenense sp. nov. is proposed. The type strain is KD51(T) ( = CGMCC 1.12432(T) = KCTC 32253(T)). An emended description of the genus Cyclobacterium is also proposed.