• 한국균학회소식:학술대회논문집
• /
• 2015.05a
• /
• pp.23-23
• /
• 2015

Plasmodiophora brassicae is a major disease threat for Brassica oil and vegetable crop production worldwide. The causal agent is a Plasmodiophorid, which are obligate biotrophic plant-pathogenic protists in the Rhizarian kingdom. Although the Plasmodiophorids include other important agricultural pathogens such as Polymyxa betae, Spongospora subterranea, their biology remains poorly understood due to their intracellular biotrophic life style. I will present the assembled and annotated genome of P. brassicae, with insights into developmental stage-specific. We provide the first genomic data for pathogenic Rhizaria. The exploitation of the life stage specific transcripts will shed light in the understanding of the life cycle at a molecular basis, which will in the long run help to understand and control club root disease. Our data also fill an important gap for the understanding of the eukaryotic tree of life, since this is only the third genome of the eukaryotic kingdom of Rhizaria.

• Journal of Species Research
• /
• v.9 no.4
• /
• pp.473-479
• /
• 2020

In this study, we briefly describe five newly recorded foraminiferal species from off the southern coast of Jeju Island: Ammolagena clavata, Neoeponides bradyi, Nodosaria lamnulifera, Rhabdammina abyssorum, and Uvigerina schwageri. Ammolagena clavata and Rhabdammina abyssorum are the first reports of the genera Ammolagena and Rhabdammina in Korea. In addition, R. abyssorum is reported from a depth of 103 m, which is a relatively shallow record within the distribution depth range for this agglutinated deep-sea species. Ammolagena clavata also shows interesting characteristics that the test usually attaches to substrates including shell fragments, sediment particles, or other foraminiferal tests. All other three species have typical calcareous and hyaline tests. The present report on unrecorded species improves the understanding of foraminiferal species diversity in Korean waters and confirms the need for the further research on foraminifera in the adjacent seas of Korea.

• Journal of Species Research
• /
• v.8 no.4
• /
• pp.389-394
• /
• 2019

Foraminifera are protists that inhabit diverse marine environments and show high abundance and diversity. However, previous studies on foraminifera in Korea mostly focused on geological and paleoecological fields and were conducted in a limited area. Therefore, there is a high possibility for discovering new and unrecorded species. Here we describe three newly recorded foraminiferal species from the southwestern part of Jeju Island during a survey on the meiofaunal community, which belongs to three different genera (Ammobaculites, Cylindroclavulina, Saracenaria), three families (Lituolidae, Vaginulinidae, Valvulinidae), and three orders (Lituolida, Textulariida, Vaginulinida): Ammobaculites formosensis Nakamura, 1937, Cylindroclavulina bradyi (Cushman, 1911), and Saracenaria hannoverana (Franke, 1936). These species have been reported from Chinese region in the East China Sea, however this is the first report from Korean waters. Particularly, Cylindroclavulina bradyi is the first report of the genus Cylindroclavulina in Korean waters. The present study supports the diversity of foraminiferal species in Korea, and the necessity of further surveys in Korean waters.

• ALGAE
• /
• v.36 no.4
• /
• pp.333-340
• /
• 2021

Phylotranscriptomics is the study of phylogenetic relationships among taxa based on their DNA sequences derived from transcriptomes. Because of the relatively low cost of transcriptome sequencing compared with genome sequencing and the fact that phylotranscriptomics is almost as reliable as phylogenomics, the phylotranscriptomic analysis has recently emerged as the preferred method for studying evolutionary biology. However, it is challenging to perform transcriptomic and phylogenetic analyses together without programming expertise. This study presents a protocol for phylotranscriptomic analysis to aid marine biologists unfamiliar with UNIX command-line interface and bioinformatics tools. Here, we used transcriptomes to reconstruct a molecular phylogeny of dinoflagellate protists, a diverse and globally abundant group of marine plankton organisms whose large and complex genomic sequences have impeded conventional phylogenic analysis based on genomic data. We hope that our proposed protocol may serve as practical and helpful information for the training and education of novice phycologists.

• Journal of fish pathology
• /
• v.24 no.3
• /
• pp.197-204
• /
• 2011

The edible ascidian Halocynthia roretzi is a commercially important fisheries resource in Korea. However, for the last several years, outbreaks of mass mortalities of the species have been occurring along the south and east coasts of Korea, where most ascidians are produced. Although it is known that tunic-softness syndrome is associated with these mortality events, the agent causing the syndrome has not yet been confirmed. To determine the agent causing tunic-softness syndrome, healthy and diseased ascidians were collected in March 2011 from Tongyeong, on the south coast of Korea, and were used for biological and pathological investigations. The results showed that diseased ascidians exhibited remarkably reduced body fluid, fatness index, and tunic index compared with healthy specimens. Interestingly, bi-flagellated protozoans were observed specifically in the tissue imprints and tunic cultures of diseased ascidians at an occurrence rate of 97.5%. Histological observation showed that the thickness of the tunics of diseased ascidians was reduced by half, and irregular structure and breakdown of the tunic fiber bundles were observed. In particular, flagellate-like cells were observed in the diseased ascidians. Our study clearly shows that bi-flagellated protists are present only in the softened ascidians, suggesting that the flagellates are partly or entirely associated with soft-tunic syndrome. Accordingly, further investigations to verify the effects of the flagellates found in the present study on soft-tunic syndrome should be conducted.

• ALGAE
• /
• v.32 no.4
• /
• pp.285-308
• /
• 2017

Cochlodinium polykrikoides red tides have caused great economic losses in the aquaculture industry in many countries. To investigate the roles of metazooplankton in red tide dynamics of C. polykrikoides in the South Sea of Korea, the abundance of metazooplankton was measured at 60 stations over 1- or 2-week intervals from May to November 2014. In addition, the grazing impacts of dominant metazooplankton on red tide species and their potential heterotrophic protistan grazers were estimated by combining field data on the abundance of red tide species, heterotrophic protist grazers, and dominant metazooplankton with data obtained from the literature concerning ingestion rates of the grazers on red tide species and heterotrophic protists. The mean abundance of total metazooplankton at each sampling time during the study was 297-1,119 individuals $m^{-3}$. The abundance of total metazooplankton was significantly positively correlated with that of phototrophic dinoflagellates (p < 0.01), but it was not significantly correlated with water temperature, salinity, and the abundance of diatoms, euglenophytes, cryptophytes, heterotrophic dinoflagellates, tintinnid ciliates, and naked ciliates (p > 0.1). Thus, dinoflagellate red tides may support high abundance of total metazooplankton. Copepods dominated metazooplankton assemblages at all sampling times except from Jul 11 to Aug 6 when cladocerans and hydrozoans dominated. The calculated maximum grazing coefficients attributable to calanoid copepods on C. polykrikoides and Prorocentrum spp. were 0.018 and $0.029d^{-1}$, respectively. Therefore, calanoid copepods may not control populations of C. polykrikoides or Prorocentrum spp. Furthermore, the maximum grazing coefficients attributable to calanoid copepods on the heterotrophic dinoflagellates Polykrikos spp. and Gyrodinium spp., which were grazers on C. polykrikoides and Prorocentrum spp., respectively, were 0.008 and $0.047d^{-1}$, respectively. Therefore, calanoid copepods may not reduce grazing impact by these heterotrophic dinoflagellate grazers on populations of the red tide dinoflagellates.

• ALGAE
• /
• v.29 no.2
• /
• pp.137-152
• /
• 2014

Mixotrophic protists play diverse roles in marine food webs as predators and prey. Thus, exploring mixotrophy in phototrophic protists has emerged as a critical step in understanding marine food webs and cycling of materials in marine ecosystem. To investigate the feeding of newly described mixotrophic dinoflagellate Ansanella granifera, we explored the feeding mechanism and the different types of species that A. granifera was able to feed on. In addition, we measured the growth and ingestion rates of A. granifera feeding on the prasinophyte Pyramimonas sp., the only algal prey, as a function of prey concentration. A. granifera was able to feed on heterotrophic bacteria and the cyanobacterium Synechococcus sp. However, among the 12 species of algal prey offered, A. granifera ingested only Pyramimonas sp. A. granifera ingested the algal prey cell by engulfment. With increasing mean prey concentration, the growth rate of A. granifera feeding on Pyramimonas sp. increased rapidly, but became saturated at a concentration of $434ngCmL^{-1}$ (10,845 cells $mL^{-1}$). The maximum specific growth rate (i.e., mixotrophic growth) of A. granifera feeding on Pyramimonas sp. was $1.426d^{-1}$, at $20^{\circ}C$ under a 14 : 10 h light-dark cycle of $20{\mu}Em^{-2}s^{-1}$, while the growth rate (i.e., phototrophic growth) under similar light conditions without added prey was $0.391d^{-1}$. With increasing mean prey concentration, the ingestion rate of A. granifera feeding on Pyramimonas sp. increased rapidly, but slightly at the concentrations ${\geq}306ngCmL^{-1}$ (7,649 cells $mL^{-1}$). The maximum ingestion rate of A. granifera feeding on Pyramimonas sp. was 0.97 ng C $predator^{-1}d^{-1}$ (24.3 cells $grazer^{-1}d^{-1}$). The calculated grazing coefficients for A. granifera feeding on co-occurring Pyramimonas sp. were up to $2.78d^{-1}$. The results of the present study suggest that A. granifera can sometimes have a considerable grazing impact on the population of Pyramimonas spp.

• Ocean and Polar Research
• /
• v.23 no.4
• /
• pp.401-410
• /
• 2001

Global climate change will alter many such properties of the Southern Ocean as temperature, circulation, stratification, and sea-ice extent. Such changes are likely to influence the species composition and activity of Antarctic marine microorganisms (protists and bacteria) which playa major role in deter-mining the concentration of atmospheric $CO_2$ and producing precursors of cloud condensation nuclei. Direct impacts of climate change on Antarctic marine microorganisms have been determined for very few species. Increasing water temperature would be expected to result in a southward spread of pelagic cyanobacteria, coccolithophorids and others. Growth rates of many species would be expected to increase slightly but nutrient limitation, especially micronutrients, is likely to result in a negligible increase in biomass. The extent of habitats would be reduced for those organisms presently living close to the upper limit of their thermal tolerance. Increased UVB irradiance is likely to favour the growth of those organisms tolerant of UVB and may change the trophic structure of marine communities. Indirect effects, especially those as a consequence of a diminution of the amount of sea-ice and increased upper ocean stratification, are predicted to lead to a change in species composition and impacts on both trophodynamics and vertical carbon flux.

• Journal of Species Research
• /
• v.6 no.spc
• /
• pp.75-93
• /
• 2017

As a part of a survey of indigenous biological resources of Korea, 30 marine benthic foraminiferal species belonging to 24 genera and seven orders (Astrorhizida, Lagenida, Lituolida, Miliolida, Robertinida, Rotaliida and Textulariida) were identified. Bottom sediment samples were collected from eight stations on the west and east coast of South Korea, in April 2015 and May 2016, respectively. Ten species belonging to nine genera and five orders (Lagenida, Lituolida, Robertinida, Rotaliida, Textulariida) were identified in the Yellow Sea. Among these taxa, Rotaliida was the dominant order, represented by four species: Evolvocassidulina tenuis (Phleger & Parker, 1951), Cibicides mabahethi Said, 1949, Cibicides pseudolabatulus Perelis & Reiss, 1975 and Cibicidoides barnetti Bermudez, 1949. Twenty species belonging to 15 genera and five orders (Astrorhizida, Lagenida, Lituolida, Miliolida, and Rotaliida) were identified from the East Sea and the Lagenida was the dominant order, represented by 11 species: Lagena strumosa Reuss, 1858, Lagena nebulosa (Cushman, 1923), Lagena striata var. semiornata Reuss, 1863, Procerolagena cylindrocostata Albani & Yassini, 1989, Fissurina bispinata $Ujii{\acute{e}}$, 1963, Oolina laevigata d'Orbigny, 1839, Polymorphina amplissima McCulloch, 1977, Polymorphina subelliptica McCulloch, 1977, Guttulina succincta McCulloch, 1977, Guttulina neoproblema McCulloch, 1977 and Lagenosolenia obtecta McCulloch, 1977. The findings described here increased the number of foraminiferal species in Korea to approximately 1060, and contribute to our understanding of the diversity of foraminifera in Korean waters.

• Journal of Environmental Health Sciences
• /
• v.40 no.4
• /
• pp.265-278
• /
• 2014

Microbes such as bacteria, fungi, archaea, protists, and viruses are ubiquitous and people are exposed to them continuously. Endotoxin is a component of the outer membrane of Gram-negative bacteria and a potent proinflammaotry substance. When a person is exposed to environmental endotoxin, an innate immune response is initiated upon the initial recognition and this response produces various inflammatory mediators and recruits inflammatory cells to the exposed tissues. A purified chemical form of endotoxin is called lipopolysaccharide (LPS), and the lipid A portion of the molecule is a biologically active moiety. Exposure to endotoxin may result in various complex health effects depending on time, route, and dose of exposure, as well as host susceptibility. Gene-environment interactions play important roles in health effects of endotoxin exposure, e.g. development or aggravation of asthma. To accurately assess exposure to endotoxin in environmental or epidemiologic studies, methods of sampling, extraction, and analysis must be carefully selected since the selected methods may substantially affect analytical results and there is no internationally-agreed standard method to date. The lack of a standardized method hampers the establishment of exposure-response relationships. While an internationally-agreed health-based exposure limit does not exist, the Dutch Expert Committee on Occupational Safety recently recommended $90EU/m^3$ as a health-based occupational exposure limit. The current article reviews various scientific issues on how we measure environmental endotoxin and the health effects of endotoxin exposure.