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454 results on '"Kim, Daekyung"'

18. Generation of Reactive Oxygen Species (ROS) by Harmful Algal Bloom (HAB)-Forming Phytoplankton and Their Potential Impact on Surrounding Living Organisms

Author

Cho, Kichul, Ueno, Mikinori, Liang, Yan, Kim, Daekyung, Oda, Tatsuya, Cho, Kichul, Ueno, Mikinori, Liang, Yan, Kim, Daekyung, and Oda, Tatsuya

Abstract

Most marine phytoplankton with relatively high ROS generation rates are categorized as harmful algal bloom (HAB)-forming species, among which Chattonella genera is the highest ROS-producing phytoplankton. In this review, we examined marine microalgae with ROS-producing activities, with focus on Chattonella genera. Several studies suggest that Chattonella produces superoxide via the activities of an enzyme similar to NADPH oxidase located on glycocalyx, a cell surface structure, while hydrogen peroxide is generated inside the cell by different pathways. Additionally, hydroxyl radical has been detected in Chattonella cell suspension. By the physical stimulation, such as passing through between the gill lamellas of fish, the glycocalyx is easily discharged from the flagellate cells and attached on the gill surface, where ROS are continuously produced, which might cause gill tissue damage and fish death. Comparative studies using several strains of Chattonella showed that ROS production rate and ichthyotoxicity of Chattonella is well correlated. Furthermore, significant levels of ROS have been reported in other raphidophytes and dinoflagellates, such as Cochlodinium polykrikoides and Karenia mikimotoi. Chattonella is the most extensively studied phytoplankton in terms of ROS production and its biological functions. Therefore, this review examined the potential ecophysiological roles of extracellular ROS production by marine microalgae in aquatic environment., Antioxidants, 11(2), art. no. 206; 2022

Published
2022

41. Zingone (Thoracosphaerales, Dinophyceae) from Korean Coastal Waters

Author

Kim, Hyun Jung, Li, Zhun, Kang, Nam Seon, Gu, Haifeng, Kim, Daekyung, Seo, Min Ho, Lee, Sang Deuk, Yun, Suk Min, Oh, Seok-Jin, and Shin, Hyeon Ho

Subjects
intercalary plate, Scrippsiella, resting cyst, ribotype, precingular plate
Abstract

The dinoflagellate genus Scrippsiella is a common member of phytoplankton and their cysts are also frequently reported in coastal sediments worldwide. However, the diversity of Scrippsiella in Korean waters has not been fully investigated. Here, several isolates of Scrippsiella precaria collected from Korean waters and germinated from resting cysts were examined using light and scanning electron microscopy. The resting cysts were characterized by pointed calcareous spines and one or two red accumulation bodies, and the archeopyle was mesoepicystal, representing the loss of 2–4′ and 1–3a paraplates. Rounded resting cysts were found in culture, and an increase in spine length was observed until 8 days of development. Korean isolates of S. precaria had the plate formula of Po, X, 4′, 3a, 7″, 6C, 4S, 5‴, 2⁗. There were differences in the cell size and location of the red body between Korean isolates and previously described cells of S. precaria. In addition, the Korean isolates of S. precaria had two types of the 5″ plate that either contacted the 2a plate or not. Molecular phylogeny based on internal transcribed spacer (ITS) and large subunit (LSU) rDNA sequences revealed that the Korean isolates were nested within the subclade of PRE (S. precaria and related species) in the clade of Scrippsiella sensu lato, and that the PRE subclade had two ribotypes: ribotype 1 consisting of the isolates from Korea, China, and Australia, and ribotype 2 consisting of the isolates from Italy and Greece. Lineages between isolates of ribotype 1 were likely to be related to the dispersal by ocean currents and ballast waters from international shipping, and the two types of spine shapes and locations of the 5″ plates may be a distinct feature for ribotype 1.

Published
2021
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45. Centrodinium punctatum (Dinophyceae) produces significant levels of saxitoxin and related analogs

Author

Shin, Hyeon Ho, Li, Zhun, Réveillon, Damien, Rovillon, Georges-augustin, Mertens, Kenneth, Hess, Philipp, Kim, Hyun Jung, Lee, Jihoon, Lee, Kyun-woo, Kim, Daekyung, Park, Bum Soo, Hwang, Jinik, Seo, Min Ho, Lim, Weol Ae, Shin, Hyeon Ho, Li, Zhun, Réveillon, Damien, Rovillon, Georges-augustin, Mertens, Kenneth, Hess, Philipp, Kim, Hyun Jung, Lee, Jihoon, Lee, Kyun-woo, Kim, Daekyung, Park, Bum Soo, Hwang, Jinik, Seo, Min Ho, and Lim, Weol Ae

Abstract

Centrodinium punctatum is a fusiform dinoflagellate with a global marine distribution. Due to a close phylogenetic relationship of one C. punctatum strain to Alexandrium species, toxin production of this C. punctatum strain was assessed using liquid chromatography coupled to tandem mass spectrometry. The paralytic shellfish toxin (PST) profile of C. punctatum was dominated by six analogs, i.e. STX (30%), GTX-1 (20%) and neoSTX (24%), followed by GTX-2 (9%), GTX-4 (9%) and GTX-3 (8%); deoxy-STX was also putatively identified while no gymnodimines, spirolides or goniodomins were detected. This is the first record of C. punctatum producing saxitoxins. The estimated cellular toxicity was rather elevated, between 91 and 212 pg cell−1 (or 259 and 601 fmol cell−1). When considering the toxicity equivalent factors, results suggest that this species can produce high cellular toxicity compared to other STX-producing dinoflagellates. Morphological details of the sulcal area and the hypotheca of Centrodinium punctatum were re-examined by scanning electron microscopy (SEM); this revealed that in the sulcal area, the left posterior sulcal plate (Ssp) is larger and longer than the left posterior sulcal plate and extended into the hypotheca. Based on the morphological observation, a revised interpretation of the sulcus and hypotheca is proposed.

Published
2020
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49. Centrodinium punctatum (Dinophyceae) produces significant levels of saxitoxin and related analogs

Author

Shin, Hyeon Ho, primary, Li, Zhun, additional, Réveillon, Damien, additional, Rovillon, Georges-Augustin, additional, Mertens, Kenneth Neil, additional, Hess, Philipp, additional, Kim, Hyun Jung, additional, Lee, Jihoon, additional, Lee, Kyun-Woo, additional, Kim, Daekyung, additional, Park, Bum Soo, additional, Hwang, Jinik, additional, Seo, Min Ho, additional, and Lim, Weol Ae, additional

Published
2020
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