• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.3
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• pp.122-127
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• 2007

Photosensitized extracts of 28 seaweed species were tested in vitro to examine the variation in their algicidal activities against the toxic microalga Cochlodinium polykrikoides. When both seaweed extracts and microalgae were exposed to UV and visible light, methanol extracts of Porphyra yezoensis showed 5.7- and 4.4-fold increasesin light-dependent algicidal activity, respectively. When only seaweed extracts were exposed to both UV (365 nm) and visible light (white lamp) at the same time, methanol extracts of Enteromorpha linza and Carpopeltis affinis showed 3.3- and 3.4-fold increases in algicidal activity, respectively. When UV-photosensitized extracts were left in the dark, the algicidal activity of Ecklonia cava increased 13-fold after 5 h. When visible light-photosensitized extracts were left in the dark, the algicidal activity of Monostroma nitidum increased by 3.3-fold in 1 h.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.3
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• pp.359-367
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• 1999

For investigating the activities of algicidal bacteria, the variations of algicidal bacterial population and chlorophyll-a were checked weekly in Chindong Bay, Korea from May to July, 1998. For identifying their killing characteristics, three strains were selected from the isolated algicidal bacteria. The density of algicidal bacteria kept changing in the range of $6.0\times10^1$ to $6.4\times10^5$ cell $\ell^{-1}$. The density flux of algicidal bacteria coincided with that of chlorophyll-a by a week of lag time. Three algicidal bacteria isolated from field strains, H519S5-4, H605S5-15 and H605S5-22, were investigated in nine microalgal species, Heterosigma akashiwo, Chattonella sp. (Raphidlphyceae), Gymnodinium catenatum, Gyrodinium impudicum, Cochlodinium polyklikoides (Dinophyceae), Chaetoceros sp., Coscinodiscus granii, Ditylum brightwellii, Thalassiosira rotula (Bacillariophyceae). Strain H605S5-22 showed a wide algicidal activities over nine microlgae, strain H605S5-15 over H. akashiwo, G. catenatum, T. rotula, Chattonella sp. and strain H519S5-4 over H. akashiwo, Chattonella sp., Chaetoceros sp., G. catenatum. The activities of the three strains were detected by the secretion of algicidal substances. Therefore, it is suggested that the activities of algicidal bacteria have a significant influence over the population dynamics of phytoplankton and get involved with the sharp decrease in red tides in the coastal area.

• Korean Journal of Ecology and Environment
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• v.49 no.3
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• pp.176-186
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• 2016

For several decades, lactic acid bacterium (Lactobacillus graminis: LAB) has been generally recognized as safe. To develop the pan-environmental bio-control agent, algicidal activity of the live LAB cell and its culture filtrate (CF) was examined against Microcystis aeruginosa. LAB cells perfectly lysed M. aeruginosa within 3 days, while the CF had a less effect than the live cells, approximately 78% inhibition of algal growth during a same culture period. The concentration of microcystin in alone culture of M. aeruginosa was $7.1{\mu}gL^{-1}$, but gradually increased and leach $158.5{\mu}gL^{-1}$ on 10 days. However, LAB cells clearly decreased the microcystin by $10.3{\mu}gL^{-1}$ in the same period, approximately 93.5%. CF of LAB showed a strong algicidal activity over 75% between pH 2-7, 91.3% by the treatment of proteinase K, 87.8% by below 3 kDa in particle size, and 75.3% by heat treatment, respectively. Of five solvents, fractions of CF passed through solvents diethyl ether and ethyl acetate showed an obvious algicidal activity in the algal-lawn test. Among 5 fractions purified by silica-gel TLC plate, two spots showed a most strong removal activity on M. aeruginosa. Another analysis of GC indicate that CF contained six representative fatty acids. Even though most of these substance have been known as an anti-algal substance against M. aeruginosa, oleic acid is the most effective. These results suggested that the culture filtrate or specific substances, like a fatty acids, in comparison with live L. graminis can be a successful and eco-friendly agent to control Microcystis bloom.

• Journal of fish pathology
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• v.16 no.3
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• pp.193-201
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• 2003

Mastoparan B (MPB), an antimicrobial cationic peptide isolated from the venom of the hornet Vespa basalis, is a basic amphipathic α-helical peptide composed of fourteen amino acid residues. In this study, we have investigated the algicidal effect of MPB against harmful algae blooms (HABs) casative Alexandrium tamarense, Chattonella marina, Cochlodinium polykrikoides and Gymnodinium catenatum. The algicidal effect of MPB showed in the concentration of 31.3 $\mu{g}$/mL to 500 $\mu{g}$/mL against 4 HAB species and observed cell lysis or cell ecdysis by microscopy. MPB reacted more sensitive to C. marina and C. polykrikoides than A. tamarense and G. catenatum. The algicidal study of MPB against HABs will provides much insight into development of new algicidal substances.

• Journal of fish pathology
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• v.17 no.2
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• pp.123-130
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• 2004

Apidaecin Ⅰb, an antimicrobial peptide isolated from lymph fluid of the honeybee (Apis mellifera), is a basic non-helical peptide composed of eighteen amino acid residues. In this study, we have investigated the algicidal effect of Apidaecin Ⅰb against harmful algae blooms (HABs) causative Alexandrium tamarense, Chattonella marina, Cochlodinium polykrikoides and Gymnodinium catenatum. The algicidal effect of Apidaecin Ⅰb showed in the concentration of 12.5 $\mu{g}/mL$ to 50$\mu{g}/mL$ against 4 HAB species and observed cell lysis or cell ecdysis by microscopy. Apidaecin Ⅰb reacted more sensitive to C. marina than A. tamarense, C. polykrikoides and G. catenatum. The algicidal study of Apidaecin Ⅰb against HABs will provides much insight into development of new algicidal substances.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.4
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• pp.331-338
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• 2000

The algicidal effects of marine bacteria were investigated and a strain, which had the strongest algicidal activity against the harmful dinoflagellate, Cochiodinim polykrikoides was selected. The bacterium was isolated in seawater during the period of blooming of C. polykrikoides in Masan Bay. This algicidal bacterium was identified as Micrococcus sp. LG-5 by means of morphological and biochemical tests. The optimal culture conditions of Micrococcus sp, LG-5 were $25^{\circ}C,\;pH 7.0\;and\;3.0{\%}$ NaCl concentration. The algicidal activity of Micrococcus sp. LG-5 was significantly increased to maximum value in the late of logarithmic phase of cell cuture. In addition, the culture filtrate ($pore size,\;0.1{\mu}m$) of Microcoocus sp. LG-5 showed strong algicidal effects. The cell numbers of C. polykikoides were decreased from $1.2{\times}10^4 cells/ml\;to\;less\;than\;2{\times}10^3\;cells/ml$ within 3, 6, 30 hours at the concentrations of culture filtrate $10{\%},\;5{\%}\;and\;1{\%}$, respectively. These results indicated that the algicidal effect was mediated by certain substances released from Microooccus sp. LG-5.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.1
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• pp.9-15
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• 2012

Worldwide development of harmful algal blooms causes serious problem for public health and fisheries industries. To evaluate the algicidal impact on the harmful algae bloom species in aquatic ecosystems of coast, a new algicide thiazolidinedione derivative (TD49) were tentatively examined in the growth stages (i.e., lag, logarithmic and stationary phase) of rapidophyceae $Heterosigma$ $akashiwo$, $Chattonella$ $marina$ and $Chattonella$ sp..Three strains could easily destroy in the lag phase due to relatively weak cell walls than those of the logarithmic and stationary phase. It is thought that inoculation of TD49 substances into initial or developmental natural blooms with a threshold concentration ($2{\mu}M$) can maximize the algicidal activity. Also, bio-chemical assays revealed that the algicidal substances from all culture strains were likely to be extracellular substances because those cells have easily destroyed in cell walls. On the other hand, natural zooplankton communities were influenced within the exposure experiments of $2{\mu}M$, which is showed the maximum algcidal activity of tested organisms. These results indicate that although the TD49 substance is potential agents for the control of $H.$ $akashiwo$, $C.$ $marina$ and $Chattonella$ sp. in the enclosed eutrophic bay and coastal water, more detailed research of acute toxicity effect on high trophic organism in marine ecosystems need to be conducted.

• Journal of Microbiology and Biotechnology
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• v.23 no.2
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• pp.260-266
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• 2013

Rhodococcus sp. strain p52, a previously isolated dibenzofuran degrader, could effectively inhibit the growth of cyanobacteria, including species of Microcystis, Anabaena, and Nodularia. When strain p52 was inoculated at the concentration of $7.7{\times}10^7$ CFU/ml, 93.5% of exponentially growing Microcystis aeruginosa ($7.3{\times}10^6$ cells/ml initially) was inhibited after 4 day. The threshold concentration for its algicidal activity against M. aeruginosa was $7.7{\times}10^6$ CFU/ml. Strain p52 exerted algicidal effect by synthesizing extracellular substances, which were identified as trans-3-indoleacrylic acid, DL-pipecolic acid, and L-pyroglutamic acid. The effective concentrations of trans-3-indoleacrylic acid and DL-pipecolic acid against M. aeruginosa were tested to be 0.5 mg/l and 5 mg/l, respectively.

• Korean Journal of Environmental Biology
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• v.36 no.3
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• pp.359-369
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• 2018

Harmful algal blooms (HABs) are a serious problem for public health and fisheries industries, thus there exists a need to investigate the possible ways for effective control of HABs. In the present study, we investigated the algicidal effects of a newly developed GreenTD against the HABs (Chattonella marina, Heterosigma akashiwo, Cochlodinium polykriokides, and Heterocapsa circularisquama) and non-HABs (Chaetoceros simplex, Skeletonema sp. and Tetraselmis sp.), which is focused on the different population density and concentration gradients of algicidal substances. The time series viability of target alga was assessed based on the activity of Chl. a photosynthetic efficiency in terms of $F_v/F_m$, and in vivo fluorescence (FSU). Effective control of Raphidophyta, C. marina and H. akashiwo was achieved at a GreenTD concentration of $0.5{\mu}gL^{-1}$ and $0.2{\mu}gL^{-1}$, respectively, and regrowth of both the species was not observed even after 14 days. The inhibitory ratio of the dinoflagellate, C. polykriokides was more than 80% at $0.2{\mu}gL^{-1}$ of GreenTD. H. circularisquama was constantly affected in the presence of $0.2{\mu}gL^{-1}$ of GreenTD in the high- and low-population density experimental groups. On the other hand, diatoms, C. simplex, and Skeletonema sp. were not significantly affected even in the presence of $0.2{\mu}gL^{-1}$ of GreenTD and exhibited re-growth activity with the passage of incubation time. In particular, green alga Tetraselmis sp. remained unaffected even in the presence of the highest concentration of GreenTD ($1.0{\mu}gL^{-1}$), implying that non-HABs were not greatly influenced by the algicidal substances. As a result, the algicidal activity of GreenTD on the harmful and nonharmful algae was as follows: raphidophyte>dinoflagellates>diatoms>green alga. Consequently, our results indicate that inoculation of GreenTD substances into natural blooms at a threshold concentration ($0.2{\mu}gL^{-1}$) can maximize the algicidal activity against HABs species. If we consider the dilution and diffusion rate in the field application, it is hypothesized that GreenTD will demonstrate economic efficiency, thus leading to effective control against the target HABs in the closed bay.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.4
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• pp.339-347
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• 2000

An algicidal bacterium, Micrococcus sp. LG-5 against the harmful dinoflagellate, Cochlodinium polykrikoides was isolated. The optimal conditions for the highest algicidal activity of bacterial culture filtrate showed in the range of $20{\~}30^{\circ}C$, at pH 7.0 and $3.0{\%}$ of NaCl concentration. In addition, $IC_(50)(mean of 50{\%} inhibitory concentration)$ of the culture filtrate against C. polykrikoides after incubation of 5 days was $0.482{\%}$. To investigate heat and pH stability of the culture filtrate of Micrococcus sp. LG-5, the culture filtrate ($pore size, 0.1 {\mu}m$) was heated to $121^{\circ}C for 15 min$ and adjusted pH from 2.0 to 10.0. There were no significant changes in algicidal activity by heat treatment and the pH change between pH from 5.0 to 10.0. The algicidal substances produced from Micrococcus sp. LG-5 were mainly detected in the fraction of $10,000{\~}1,000$ MWCO (molecular weight cut-off). The culture filtrate of Micrococous sp. LG-5 showed antimicrobial activity against Enterococcus faecalis, Escheiichia coli, Uebsiella pneunioniae and Vibrio altinolyticus, but did not show against Pseudomonas aeminosa, P. Buorescens, Salmonella typhi, Staphylococcus aureus, V. cholerae and V parahaemolyicus. The culture filtrate of Micrococcus sp. LG-5 was examined against 16 phytoplankton species and showed the algicidal activity against Ajexandzium tuarense, Eutreptiella Drnnastin, Gymnodinium catenatum, G. mikimotoi, G. sanguineum, eyodinium impuaicum, Heterocapsa triquetra, Heterosipa akashiwo, Prorocentrum micans and Pyraminonas sp.. However no algicidal effects of Micrococcus sp. LG-5 were observed against Chlamydomonas sp., Cylindrotheoa closterium, P. mininum, P. triestimum, Pseudonieschia sp. and Sczipuiella trochoidea. On the other hand, algicidal activity on the tested marinelivefood was not detected except for Isochrysis galbana. In addition, physiological responses of cultured olive flounder (Paralichthys oliraceus) exposed to $1 and 10{\%}$ of the culture filtrate of Micrococcus sp. LG-5 were measured. There were no clear changes in AST, GGT, creatinine, urea, total cholesterol, total protein, albumine, $Mg^(+2), Ca^(+2), Na^+, K^+, and Cl^-$. These results indicate that olive flounders were not affected when they were exposed to the culture filtrate of Micrococcus sp. LG-5.