• ALGAE
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• v.30 no.4
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• pp.281-290
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• 2015

We explored phagotrophy of the phototrophic ciliate Mesodinium rubrum on the cyanobacterium Synechococcus. The ingestion and clearance rates of M. rubrum on Synechococcus as a function of prey concentration were measured. In addition, we calculated grazing coefficients by combining the field data on abundance of M. rubrum and co-occurring Synechococcus spp. with laboratory data on ingestion rates. The ingestion rate of M. rubrum on Synechococcus sp. linearly increased with increasing prey concentrations up to approximately 1.9 × 10⁶ cells mL^-1, to exhibit sigmoidal saturation at higher concentrations. The maximum ingestion and clearance rates of M. rubrum on Synechococcus were 2.1 cells predator^-1 h^-1 and 4.2 nL predator^-1 h^-1, respectively. The calculated grazing coefficients attributable to M. rubrum on cooccurring Synechococcus spp. reached 0.04 day^-1. M. rubrum could thus sometimes be an effective protistan grazer of Synechococcus in marine planktonic food webs. M. rubrum might also be able to form recurrent and massive blooms in diverse marine environments supported by the unique and complex mixotrophic arrays including phagotrphy on hetrotrophic bacteria and Synechococcus as well as digestion, kleptoplastidy and karyoklepty after the ingestion of cryptophyte prey.

• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.510-517
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• 2005

The filamentous cyanobacterium Anabaena is capable of both photosynthesis and nitrogen fixation which probably facilitated its incredible adaptation and proliferation in freshwater environments. A small gene, patS, was found to block nitrogen fixing cells from developing which resulted in death of Anabaena in the absence of combined nitrogen sources. We analyzed the DNA sequences in the vicinity of the patS gene by using a codon usage program and detected no codon bias other than the patS open reading frame. Three overlapping cosmids that contain the patS gene were identified, and the presence of other known heterocyst-controlling genes was examined. The patS expression in response to nitrogen starvation was analyzed at the level of transcription and translation by using Northern blot analyses and lacZ-reporter-gene fusion experiments, respectively. The patS expression increased rapidly (within 12 hours) upon the removal of combined nitrogen from the media.

• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.494-502
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• 2005

Antialgal bacteria and ciliates were tested alone and in combination for their abilities to decrease the densities of the warm-weather cyanobacterium, Microcystis aeruginosa, and the cold-weather centric diatom, Stephanodiscus hantzschii. Our results indicate that the density of M. aeruginosa was effectively suppressed by the bacterium, Streptomyces neyagawensis, and the heterotrich ciliate, Stentor roeselii. However, co-treatment with both bio-agents stimulated the algal density rather than decreasing it, suggesting that S. neyagawensis and S. roeselii may have an antagonistic relationship. Additional experiments revealed that the density of S. hantzschii was effectively suppressed by the bacterium, Pseudomonas putida, and by the above mentioned strain of S. roeselii. Co-treatment with both bio-agents had a higher antialgal activity than treatment with each alone, indicating that the bio-agents may act synergistically. These results suggest that the anti-alge efficacy of co-treatment with multiple biological control agents is likely to differ depending on the bio-agents and target organisms.

• ALGAE
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• v.35 no.2
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• pp.177-187
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• 2020

Cyanobacteria have been widely reported to produce a variety of UV-absorbing mycosporine-like amino acids (MAAs). Herein, we reported production of the unusual MAA, mycosporine-glycine-alanine (MGA) in the cyanobacterium Sphaerospermopsis torques-reginae ITEP-024 using a newly developed UHPLC-DAD-MS/HRMS (ultra-high performance liquid chromatography-diode array detection-high resolution tandem mass spectrometry) method. MGA had previously been first identified in a red-algae, but S. torques-reginae strain ITEP-024 is the first cyanobacteria to be reported as an MGA producer. Herein, the chemical structure of MGA is fully elucidated from one-dimensional / two-dimensional nuclear magnetic resonance and HRMS data analyses. MAAs are unusually produced constitutively in S. torques-reginae ITEP-024, and this production was further enhanced following UV-irradiance. It has been proposed that MAA biosynthesis proceeds in cyanobacteria from the pentose phosphate pathway intermediate sedoheptulose 7-phosphate. Annotation of a gene cluster encoded in the genome sequence of S. torques-reginae ITEP-024 supports these gene products could catalyse the biosynthesis of MAAs. However, addition of glyphosate to cultures of S. torques-reginae ITEP-024 abolished constitutive and ultra-violet radiation induced production of MGA, shinorine and porphyra-334. This finding supports involvement of the shikimic acid pathway in the biosynthesis of MAAs by this species.

• Korean Journal of Ecology and Environment
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• v.48 no.4
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• pp.287-295
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• 2015

Akinete germination potential and algal growth potential (AGP) using Anabaena circinalis were investigated September 2014 and March 2015 at the three sites (PD-1, PD-2 and PD-3) of Lake Paldang. Nitrogen and phosphorus concentrations were higher at PD-2 than at PD-1 and PD-3. TSI (TN) values at the three field sites were in the range of 65~85, which were the level of eutrophic or hypereutrophic state. TSI (TP) also showed high values (49~68), which were the level of mesotrophic or eutrophic state. Akinete germination potential was higher at PD-2 with increased nutrient (nitrogen and phosphorus), and algal growth potential also increased with nutrient enrichment.

• Journal of Life Science
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• v.12 no.2
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• pp.158-163
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• 2002

For axenic isolation of the cyanobacterium Microcystis aeruginosa, water bloom at the Mulgum station from the Nakdong River was pretreated by shaking with distilled water. Removal of bacteria was accomplished using antibiotics (150 $\mu$g/$m\ell$ ampicillin and 25 $\mu$g/$m\ell$ neomycin) and colonizing on CB solid medium prepared from 0.7% agarose at 3$0^{\circ}C$ under 40 $\mu$ mol m$^{-2}$ s$^{-1}$ light. Among 26 strains of the Microcystis species, only three strains were axenically established. The three strains were examined by PCR-amplified 16S rRNA gene and 16S rRNA sequencing. The similarities were 99.5 ~100% with M. aeruginosa AF 139292.

• Journal of Microbiology and Biotechnology
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• v.32 no.10
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• pp.1325-1334
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• 2022

Global warming has accelerated in recent decades due to the continuous consumption of petroleum-based fuels. Cyanobacteria-derived biofuels are a promising carbon-neutral alternative to fossil fuels that may help achieve a cleaner environment. Here, we propose an effective strategy based on the large-scale cultivation of a newly isolated cyanobacterial strain to produce phycobiliprotein and biodiesel, thus demonstrating the potential commercial applicability of the isolated microalgal strain. A native cyanobacterium was isolated from Goryeong, Korea, and identified as Pseudanabaena mucicola GO0704 through 16s RNA analysis. The potential exploitation of P. mucicola GO0704 was explored by analyzing several parameters for mixotrophic culture, and optimal growth was achieved through the addition of sodium acetate (1 g/l) to the BG-11 medium. Next, the cultures were scaled up to a stirred-tank bioreactor in mixotrophic conditions to maximize the productivity of biomass and metabolites. The biomass, phycobiliprotein, and fatty acids concentrations in sodium acetate-treated cells were enhanced, and the highest biodiesel productivity (8.1 mg/l/d) was achieved at 96 h. Finally, the properties of the fuel derived from P. mucicola GO0704 were estimated with converted biodiesels according to the composition of fatty acids. Most of the characteristics of the final product, except for the cloud point, were compliant with international biodiesel standards [ASTM 6761 (US) and EN 14214 (Europe)].

• Journal of Microbiology
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• v.35 no.4
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• pp.284-289
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• 1997

A Gram (-), rod-shaped bacterium $2.3{\sim}2.8{\times}0.45{\mu}m$ in size which exhibited growth-inhibiting effects against a cyanobacterium (Anabaena cylindrica) was isolated from Daechung Dam Reservoir. This isolate was identified as Moraxella sp. and designated Moracella sp. CK-1. Hollow zones formed around bacterial colonies on the cyanobacterial lawn. In a mixed-culture of A. cylindrica and the isolate, each microorganism grew inverse-proportionally, and the cyanobacterial vegetative cells completely disappeared within 24 hours. On treatment with Moraxella sp. CK-1, cell walls of A. cylindrica disappeared, but sheathes remained in a more electron dense form. The unit membrane such as thylakoidal membrane was stable to bacterial lysing activity. This bacterium showed a broad action spectrum against cyanobacteria. The growth-inhibiting activity of Moracella sp. CK-1 against A. cylindrica is believed to be performed through the excretion of active substances.

• Journal of Photoscience
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• v.9 no.2
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• pp.367-369
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• 2002

Chlorophyll (ChI) a' is the Cl3$^2$-epimer of ChI a which is the constituent of P700, the primary electron donor of Photosystem (PS) I, of a thrmophilic cyanobacterium, Synechococcus elongatus, whose structure was recently determined by X-ray crystallography. To determine whether PS I of diverse oxygenic photosynthetic organisms universally contain one molecule of ChI a ’, pigment compositions of thylakoid membranes and PS I complexes isolated from cyanobacteria, green algae, red algae and higher plants were determined by reversed-phase HPLC. The results show that involvement of one ChI a'molecule in PS I is the universal feature for Chi a-based PS I of oxygenic photosynthetic organisms.

• Journal of Microbiology and Biotechnology
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• v.7 no.5
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• pp.341-344
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• 1997

Batch cultures of Anacystis nidulans BD-1 resistant to azaleucine and fluorotyrosine produced and liberated a wide range of amino acids, notably glutamic acid, alanine, phenylalanine, leucine, isoleucine, cysteine and methionine. Sustained liberation for prolonged periods was achieved after immobilization on calcium alginate and the net concentration in the medium was 0.18-0.2 g $I^{-1}$. While acetohydroxy acid synthase in azaleucine-resistant mutant lost leucine- and isoleucine-sensitivity, fluorotyrosine-resistant strain turned phenylalanine activating. The activities of nitrate assimilating enzymes were also higher in the mutants and were relaxed from ammonium-repression. The metabolic adjustments involved in amino acid overproduction are discussed.