ABSTRACT
A new bacterial strain designated DH39T was isolated from marine sediment collected from the East Sea, Korea. Phylogenetic analysis using the 16S rRNA gene sequence revealed that strain DH39T clustered with the genus Shewanella and is closely related to Shewanella canadensis HAW-EB2T, S. woodyi MS32T, and S. sediminis HAW-EB3Twith 98.1, 97.8, and 97.6% sequence similarities, respectively. The isolated bacterium was Gram-negative, rod-shaped, and aerobic. Its temperature range for growth was 4–30°C. The predominant fatty acids were 16:1w7, 17:1w8, 13:0-i, 16:0, and 15:0-i. The DNA G+C content was 45.0 mol%. DNA-DNA hybridization analysis showed that DNA-DNA relatedness values in the 16S rRNA phylogenetic tree of strain DH39T and its nearest neighbors S. hanedai and S. sediminis were 52.9 and 58.7%. Phylogenetic evidence and phenotypic characteristics suggest strain DH39T constitutes a novel Shewanella species. Therefore, we propose Shewanella marinisediminis sp. nov., with DH39T (KCCM 42936T = NCCB 100311T) as the type strain.
ABSTRACT
The diurnal vertical migration of Cochlodinium polykrikoides (C. polykrikoides), which caused a red tide in the Korean coastal waters of the East Sea/Sea of Japan in September 2003, was examined by determining the time-dependent changes in the density of living cells in relation to the depth of the water column. The ascent of this species into the surface layer (depth of water, 2 m) occurred during 1400- 1500. The descent started at 1600 and a high distribution rate (86%) at 15-20 m was observed at 0300. During the ascent, the cells were widely distributed at each depth level from 0600 hr and at 0800-1100, the cells were primarily distributed in the middle layer (0-6 m). The concentration of dissolved inorganic nitrogen was generally <2.86 μmol l -1, but at 1400-1500, the concentration in the surface layer reduced to <0.14 μmol l -1. Moreover, the concentration gradually increased as the depth increased to > 5 m. These results showed that the nutrientconsumption rate associated with the proliferation of C. polykrikoides during a red tide is more influenced by the inorganic-nitrogen resources rather than the inorganic-phosphorus compounds.