Mesonia maritimus sp . nov . , isolated from seawater of the South Sea of Korea

A yellow-pigmented bacterial strain, originally designated 15-S14-6, was isolated from the southern coastal waters of Korea and was subjected to taxonomic study using a polyphasic approach. Strain 15-S14-6 was Gram-staining-negative, flagellated, rod-shaped and aerobic. The strain grew optimally at 25–30 C, in the presence of 2% (w/v) NaCl and at pH 7.5– 8.0. The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that 15-S14-6 represented a member of the genus Mesonia and exhibited the highest sequence similarity (98.0%) with Mesonia aquimarina IMCC1021, followed by Mesonia mobilis KMM 6059 (96.7%) and Mesonia phycicola MDSW-25 (96.1%). DNA–DNA relatedness between 15-S14-6 and M. aquimarina IMCC1021 was 11.2±1.6% (12.3±0.3% in a reciprocal experiment). Strain 15-S14-6 had a DNA G+C content of 34.4mol% and had MK-6 as the predominant menaquinone. Furthermore, iso-C15 : 0, iso-C17 : 0 3-OH and summed feature 3 were identified as the major fatty acids. Phosphatidylethanolamine, two unknown aminolipids, an unknown phospholipid and four other unknown lipids were determined to be the major polar lipids. Based on phenotypic properties and phylogenetic data presented here, 15-S14-6 is considered to represent a novel species of the genus Mesonia, for which the name Mesonia maritimus sp. nov. is proposed. The type strain is 15-S14-6 (= KCCM 43197, NCAIM B.02633, CGMCC 1.16020). The genus Mesonia (as a member of the family Flavobacteriaceae, within the phylum Bacteroidetes) was first proposed in 2003 by Nedashkovskaya et al. [1], with the description of Mesonia algae KMM 3909. At the time of writing this manuscript, the genus Mesonia was comprised of seven species, with validly published names [2]: Mesonia algae [1], Mesonia mobilis [3], Mesonia phycicola [4], Mesonia ostreae [5], Mesonia aquimarina [6], Mesonia hippocampi [7] and Mesonia sediminis [8]. Type strains of species of the genus Mesonia have been isolated from diverse marine environments and microhabitats, as exemplified by the following: sea water and green algae of the species Acrosiphonia sonderi in the East Sea [1, 3], an oyster farm in the South Sea of Korea [5] and off the East Sea of Korea [6], seaweeds near the Mara Island, Republic of Korea [4], the brood pouch of a male seahorse of the species Hippocampus barbouri in Germany [7] and a sea cucumber culture pond in Rongcheng, PR China [8]. Members of the genus Mesonia are described as Gramstaining-negative, rod shaped, strictly aerobic bacteria that do not form endospores. Sodium ions are required for growth. Menaquinone-6 (MK-6) is the major respiratory quinone and predominant cellular fatty acids are characterized by straightand branched-chain unsaturated fatty acids [9]. The G+C content of the genomic DNA is in the range 30–42.1mol% [5]. During an investigation on the cultivable bacterial diversity of a seawater sample from the Southern Sea area, Republic of Korea, a number of novel bacteria were isolated and taxonomically characterized. This study is focused on a bacterial strain designated 15-S14-6, originally isolated from the surface seawater sampled off the Tongyeong coast (34 50¢ 34.0† N, 128 26¢ 43.9† E) in December 2014. The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that this strain represented a member of the genus Mesonia. The aim of this study was to determine the exact taxonomic position of 15-S14-6, by using a polyphasic approach that included morphological, physiological, biochemical and chemotaxonomic characterization, as well as phylogenetic analysis. Seawater samples were serially diluted (10-fold dilution) and 0.1ml aliquots of each dilution were plated onto half strength marine agar 2216 (MA; BD) [10] and incubated at 25 C for 7 days. A glistering yellow colony of 15-S14-6 was isolated and purified by repeated streaking on fresh MA Author affiliations: Industrial Bio-materials Research Center, KRIBB, Daejeon 305-806, Republic of Korea; Department of Bioscience and Biotechnology, Hankuk University of Foreign Studies, Wangsan, Yongin, Gyeonggi 449-791, Republic of Korea. *Correspondence: Kee-Sun Shin, ksshin@kribb.re. kr