wonho yih - Academia.edu (original) (raw)

Papers by wonho yih

Journal of Marine Science: Research & Development, Jun 27, 2015

Quadruplicate cultures in 500 ml-PC bottles were subsampled to measure chlorophyll fluorescence e... more Quadruplicate cultures in 500 ml-PC bottles were subsampled to measure chlorophyll fluorescence every 24 hrs. A total of 32 culture bottles (quadruplicate bottles for 8 SS concentrations) were prepared and incubated at 20°C, 30 psu under 50 μE m-2 s-1 using rotating wheels (4 rpm) for each of the 3 test strains, a cryptomonad, a diatom Skeletonema sp. and a dinoflagellate Prorocentrum minimum. In all the three test strains, population size steadily increased at least during the first 3 days regardless of the SS concentrations in the culture media, followed by retarded growth (a cryptomonad and Prorocentrum minimum) or population decline (Skeletonema sp.). Mean daily growth rates during the first 3 d along the SS concentration gradient were compared within each strain as well as among the strains. Skeletonema sp. and a cryptomonad exhibited positively related growth rate with SS concentrations while P. minimum did negatively. Present result implies that the increased SS concentration may sometimes stimulate population growth of non-flagellated or nano-flagellate protists in contrasts to the case of dinoflagellates. Extended speculation might open an early discussion on the potentially negative effect of the increased SS concentrations on red-tide dinoflagellate species.

The Korean Society Of Limnology, Sep 1, 2005

The Korean Society Of Oceangraphy, Nov 1, 2007

Korea Institute of Ocean Science & Technology, Mar 1, 2019

At the estuaries of Bonggang and Miryong streams in the Korean southern coast, the spatiotemporal... more At the estuaries of Bonggang and Miryong streams in the Korean southern coast, the spatiotemporal distribution and habitat environment of a nerite snail, Clithon retropictum (Gastropoda: Neritidae), which has been assigned as a legally protected species of Korea, were explored. Physicochemical environmental factors such as water temperature, salinity, tidal level distribution as well as biotic environments (chlorophyll-a concentration and epilithic microalgae composition) were monitored every month. The relationships between the environmental factors and spatiotemporal distribution of the nerite snail population were analyzed. Water temperature, salinity, and water level varied by season and lunar tidal rhythm. The spatiotemporal distribution of the nerite snail was mostly related to water salinity. Among epilithic algae which were the priority prey of snails, blue-green algae and green algae dominated in summer and autumn, while diatoms predominated during winter and spring. Chloro...

Journal of Ecology and Environment, 2006

The Sea, 2016

We investigated the occurrence of the dinoflagellate genus Alexandrium in the nineteen Korean coa... more We investigated the occurrence of the dinoflagellate genus Alexandrium in the nineteen Korean coastal sites from July to October 2013. Alexandrium-like planktonic cells were microscopically observed only in four out of the 19 sampling sites. From the samples containing Alexandrium-like cells 22 clonal cultures of Alexandrium species were established by single cell or single chain isolation method. Taxonomic identity of the 4 different strains ascertained by the robust analyses of morphological and molecular genetic characteristics were confirmed to be A. catenella, A. affine, A. fraterculus and an unidentified Alexandrium sp. for which strain WEB-Alex-01 was assigned. It was ascertained that in spite of hot summer diverse Alexandrium species attaining up to four were distributed in the study area, in contrast with the long empirical recognition that the emergence of Alexandrium species is restricted to cooler seasons like spring or autumn in Korean coastal waters. Morphology and genetic characteristics of Alexandrium sp. strain WEB-Alex-01 are different from any other previously reported Alexandrium species from Korean seas, which implies that further studies on taxonomic, physiological, ecological and toxicological properties of the newly recorded Alexandrium species are needed.

Among various microscopic organisms producing photobiological hydrogen, cyanobacteria have long b... more Among various microscopic organisms producing photobiological hydrogen, cyanobacteria have long been recognized as the promising biological agents for hydrogen economy in 21 century. For photobiological production of hydrogen energy, marine unicellular -fixing cyanobacteria have been evaluated as an ideal subgroup of Cyanophyceae. To develope the hydrogen production technology using unicellular -fixing cyanobacteria, 3 important factors are pre-requisite: 1) isolation of the best strain from marine natural environment, 2) exploration on the strain-specific optimal conditions for the photobiological hydrogen production, and finally 3) application of the molecular genetic tools to improve the natural ability of the strain to produce hydrogen. Here we reviewed the recent research & development to commercialize photobiological hydrogen production technology, and suggest that intensive R&D during next 10-15 years should be imperative for the future Korean initiatives in the field of the photobiological hydrogen production technology using photosynthetic marine unicellular cyanobacterial strains.

Photobiological hydrogen production by nitrogen-fixing unicellular cyanobacteria has long been co... more Photobiological hydrogen production by nitrogen-fixing unicellular cyanobacteria has long been considered to be an environmentally sound and very promising method for the future supply of renewable clean energy. We tried to find out the optimum cell concentration for H2 production in each of the two new Korean nitrogen-fixing unicellular cyanobacterial strains to compare with Synechococcus sp. strain Miami BG043511. The two Korean strains, Cyanothece sp. KNU CB MAL-031 and KNU CB MAL-058, were isolated from Korean west coasts. Cell concentrations up to 17 billion cells ml-1 were applied to the tests. High cell concentration over 15 billion cells ml-1 resulted in drastically reduced H 2 production in all the three strains. The two domestic strains, however, produced 2-3 time more hydrogen than Synechococcus sp. Miami BG043511 at cell concentrations of 5-10 billion cells ml-1. At lower cell concentrations than 2 billion cells ml-1 , MAL-031 exhibited highest H2 production followed by Miami BG043511, with far less production in MAL-058. Present result suggests that Cyanothece sp. MAL-CB031 might be one of the ideal nitrogen-fixing unicellular cyanobacterial strains for the photobiological hydrogen production.

Harmful Algae, 2016

Photosynthesis in the ciliate Mesodinium rubrum is achieved using a consortium of cryptophyte alg... more Photosynthesis in the ciliate Mesodinium rubrum is achieved using a consortium of cryptophyte algal organelles enclosed in its specialized vacuole. A time-series microarray analysis was conducted on the photosynthetic ciliate using an oligochip containing 15,654 primers designed from EST data of the cryptophyte prey, Teleaulax amphioxeia. The cryptophycean nuclei were transcriptionally active over 13 weeks and approximately 13.5% of transcripts in the ciliate came from the sequestered nuclei. The cryptophyte nuclei and chloroplasts could divide in the ciliate, which were loosely synchronized with host cell division. A large epigenetic modification occurred after the cryptophyte nuclei were sequestered into the ciliate. Most cryptophyte genes involved in the light and dark reactions of photosynthesis, chlorophyll assimilation, as well as in DNA methylation, were consistently up-regulated in the ciliate. The imbalance of division rate between the sequestered cryptophyte nuclei and host nuclei may be the reason for the eventual cessation of the kleptoplastidy.

Bulletin of the Korean Chemical Society, 2015

Marine dinoflagellates have been widely studied because of their rich chemodiversity and biologic... more Marine dinoflagellates have been widely studied because of their rich chemodiversity and biologically toxic compounds extracted from them. These organisms are considered the cause of most occurrences of food poisoning from seafood. 1-3 Among these, the genera Prorocentrum and Dinophysis were well known to produce diarrhetic shellfish poisoning (DSP) toxins such as the okadaic acid (OA), pectenotoxin-2 (PTX-2), and dinophysistoxin-1 (DTX-1), leading to disastrous influences on the shellfish industry worldwide due to their effect on human health. 4-6 Shellfish are believed to become toxic by accumulating the toxins through filterfeeding the algae of the two genera. Furthermore, many research works have also revealed the existence of a wide range of OA analogs from the large-scale cultivation or filter-feeding bivalve molluscs, such as scallops, clams, and mussels. The OA analogs are largely classified into 7-O-fatty acid esters, which are found only in shellfish, and diol esters, where the carboxylic group of OA is esterified with C 6 to C 10 diols. All of these constituents may be very important in the study of toxin production and toxin profile of shellfish or harmful algae in coast areas. 7-9 Recently, during the monitoring of toxic compounds from the benthic Prorocentrum lima spawned around Jeju island, Korea, an unidentified DTX-1 analog (1) was isolated from the toxic fractions of the cultures of P. lima and structurally characterized. This new compound is characterized by a lipid-soluble C 9 diol ester of DTX-1. As shown in Figure 1, most of the lipid-soluble diol esters previously reported in the literature are commonly derived from the OA parent compound. 10-15 Interestingly, on the other hand, 1 came from the DTX-1 compound. The 7-O-fatty acid esters of DTX-1, collectively named as DTX-3, have been found, 4 but, to our knowledge, diol esters of DTX-1, such as compound 1, have not been reported. In this paper, we present the cultivation method of P. lima, the characterization of compound 1, and its bioactivity. The methanolic extract of P. lima, exhibiting strong cytotoxicity during a brine shrimp lethality test, showed in the liquid chromatography-mass spectrometry (LC-MS) analysis the presence of two well-known DSP toxins: OA and DTX-1.

PloS one, 2015

Teleaulax amphioxeia is a photosynthetic unicellular cryptophyte alga that is distributed through... more Teleaulax amphioxeia is a photosynthetic unicellular cryptophyte alga that is distributed throughout marine habitats worldwide. This alga is an important plastid donor to the dinoflagellate Dinophysis caudata through the ciliate Mesodinium rubrum in the marine food web. To better understand the genomic characteristics of T. amphioxeia, we have sequenced and analyzed its plastid genome. The plastid genome sequence of T. amphioxeia is similar to that of Rhodomonas salina, and they share significant synteny. This sequence exhibits less similarity to that of Guillardia theta, the representative plastid genome of photosynthetic cryptophytes. The gene content and order of the three photosynthetic cryptomonad plastid genomes studied is highly conserved. The plastid genome of T. amphioxeia is composed of 129,772 bp and includes 143 protein-coding genes, 2 rRNA operons and 30 tRNA sequences. The DNA polymerase III gene (dnaX) was most likely acquired via lateral gene transfer (LGT) from a fi...

Journal of Eukaryotic Microbiology, 2014

Mesodinium is a globally distributed ciliate genus forming frequent and recurrent blooms in diver... more Mesodinium is a globally distributed ciliate genus forming frequent and recurrent blooms in diverse marine habitats. Here, we describe a new marine species, Mesodinium coatsi n. sp., originally isolated from interstitial water of surface sand samples collected at Mohang Beach, Korea. The species was maintained under a mixotrophic growth condition for longer than 1 yr by providing a cryptomonad, Chroomonas sp., as the sole prey. Cell morphology and subcellular structure were examined by light microscopy, scanning, and transmission electron microscopy, and molecular phylogeny was inferred from nuclear-encoded 18S rDNA sequence data. Like other Mesodinium species, M. coatsi consisted of two hemispheres separated by two types of kinetids, and had tentacles located at the oral end of the cell. Several food vacuoles were observed in the cytoplasm, and partially digested prey cells sometimes existed in food vacuoles. Kinetids and the associated accessory structures were quite similar to those previously reported, but M. coatsi was differentiated from other marine Mesodinium species by ultrastructural characters of the dikinetids, polykinetids, and tentacles. We also provided a detailed illustration of infraciliature. Molecular phylogeny revealed that M. coatsi and Mesodinium chamaeleon were closely related to each other.

Ocean and Polar Research, 2009