The genus Roseovarius accommodates Gram-negative, ovoid or rod-shaped, obligate aerobic alphaproteobacteria and all its members are positive in tests for catalase. All of the species were retrieved from marine environments and belong to the Roseobacter group. Many novel representatives of this group have been isolated from marine habitats all over the world and described recently (Wagner-Döbler et al., 2003;Buchan et al., 2005;Dai et al., 2006;Lee et al., 2007;Hwang & Cho, 2008). In this paper, a novel Gram-negative, beige-to slightly pink-pigmented, aerobic bacterium is described that was isolated from sediment of the South China Sea. By using 16S rRNA gene sequence phylogenetic analysis, the new strain was determined to be a member of the Roseobacter group, in which it formed a distinct lineage with members of the genus Roseovarius. Based on differences in fatty acid composition, physiological and biochemical characteristics, morphological features, and phylogenetic analysis as described in this study, the new strain should be classified as a novel species of the genus Roseovarius.Recently, bacterial diversity investigations have led to the discovery of many novel species and genera from the South China Sea. One of these strains, designated NH52JT , was isolated from a brown sandy sediment sample (109 u 40.1029 E, 06 u 5.9019 N), which was collected at water depth of 157 m in June 2007. In the laboratory, the sediment sample was suspended and diluted (1 : 100) using sterilized seawater, spread onto M2 agar plates and then incubated at 25 u C for 1 week. The composition of M2 medium was (l 21 seawater): 5 g CH 3 COONa, 0.5 g peptone, 0.5 g yeast extract, 0.5 g glucose, 0.5 g sucrose, 0.5 g starch, 0.05 g trisodium citrate, 0.05 g malic acid, 0.05 g potassium sodium tartrate, 1.0 g NH 4 NO 3 , 0.2 g NH 4 Cl and 15 g agar, adjusted to pH 7.5-7.6. Strain NH52JT was picked and streaked on fresh M2 agar medium. This process was repeated three times for purification and the strain was preserved as a 20 % (v/v) glycerol suspension at 280 u C. Cell morphology and motility were observed by phase-contrast microscopy Abbreviation: Bchl a, bacteriochlorophyll a.3These authors contributed equally to this work.The GenBank accession number for the 16S rRNA gene sequence of Roseovarius nanhaiticus sp. nov. NH52JT is FJ403243.

An aerobic, Gram-staining-negative, motile, rod-shaped bacterium, strain NH52F T , was isolated from a sandy sediment sample taken from the South China Sea. On M2 agar medium (a complex medium), colonies were beige in colour. The isolate showed highest 16S rRNA gene sequence similarities to members of the genera Leisingera (96.7 % similarity), Phaeobacter (95.4-96.0 %) and Marinovum (94.1 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain NH52F T formed a distinct cluster with Leisingera methylohalidivorans MB2 T and Leisingera aquimarina LMG 24366 T . Optimal growth was observed at pH 7.0-8.5 and 25 6C and the new isolate required the presence of 1-4 % (w/v) NaCl. The major fatty acids were C 18 : 1 v7c, C 16 : 0 2-OH, C 10 : 0 3-OH, C 12 : 0 3-OH, C 16 : 0 and 11-methyl C 18 : 1 v7c. The DNA G+C content was 60.5 mol%. The phylogenetic and chemotaxonomic characteristics of strain NH52F T were similar to those of the genus Leisingera. However, the differences in phenotypic properties and the 16S rRNA gene similarity values demonstrated that the new isolate differed from recognized species of the genus Leisingera. On the basis of phenotypic, chemotaxonomic and phylogenetic data, this organism should be classified as a representative of a novel species in the genus Leisingera, for which the name Leisingera nanhaiensis sp. nov. is proposed. The type strain is NH52F T (5LMG 24841 T 5CCTCC AB 208316 T 5MCCC 1A04178 T ).

A taxonomic study was carried out on strain 3PC125-7, which was isolated from the deep sea water of the Indian Ocean. The bacterium was rod-shaped, non-flagellated, Gram-stain-negative, oxidase- and catalase-positive and strictly aerobic. Optimal growth was observed at 25-37 °C, at pH 7 and in 1-3 % (w/v) NaCl. On the basis of the results of 16S rRNA gene sequence analysis, strain 3PC125-7 represents a member of the genus Muricauda, with the highest sequence similarity to Muricauda olearia CL-SS4 (96.7 %), followed by Muricauda marina H19-56 (96.7 %) and nine other species of the genus Muricauda(93.5-95.8 %). The principal fatty acids of 3PC125-7 were iso-C15 : 0, iso-C17 : 0 3-OH and iso-C15 : 1G and the sole respiratory quinone was menaquinone-6. The polar lipids comprise phosphatidylethanolamine, six unidentified phospholipids and three unknown lipids. The genomic DNA G+C content of 3PC125-7 was 41.8 mol%. Based on the phylogenetic, phenotypic and chemotaxonomic data obtained in this study, strain 3PC125-7 is considered to represent a novel species in the genus Muricauda, for which the name Muricaudaindica sp. nov. is proposed, with the type strain 3PC125-7 (=MCCC 1A03198=KCTC 52318).