• Journal of Korean Society on Water Environment
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• v.33 no.5
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• pp.538-545
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• 2017

The purpose of this study is to investigate growth response and toxigenicity under various temperature and nutritional conditions, in order to understand the physioecological characteristics of Aphanizomenon flos-aquae, which is a bloom-forming cyanobacterium in the Nakdong River. The strain was inoculated into media under combinations of four temperatures (4, 12, 21, $30^{\circ}C$) and three nutrients (modified CB medium, P-depleted CB medium, N-depleted CB medium) for 28 days. The algae-inhibition tests were performed to assess the potential allelopathic effects of the strains' filtrates on the growth of four algae strains (Microcystis aeruginosa, Aulacoseria ambigua f. spiralis, Aphanizomenon flos-aquae, Scenedesmus obliquus). Toxin production of a strain was measured by Enzyme-Linked ImmunoSolbent Assay (ELISA). The optimal growth temperature (Topt) of strains was $19.9^{\circ}C$ ($18.3-21.2^{\circ}C$), and the temperature range for growth was from $-0.3^{\circ}C$ to $34.3^{\circ}C$. Specific growth rate (${\mu}$) in modified CB medium varied from 0.10 to $0.16day^{-1}$, and the maximum growth rate (${\mu}_{max}$) was $0.17day^{-1}$. Although growth curves under N-existed and N-depleted conditions were almost the same, growth under N-depleted condition was relatively slowed (${\mu}=0.09$ to $0.14day^{-1}$), with a decreased maximum cell density. However, growth under the P-depleted condition was restricted for all temperatures, Two stains of Aphanizomenon flos-aquae were confirmed as not producing toxins, because saxitoxin and cylindrospermopsin were not detected by ELISA. The exudates or filtrates from the Aphanizomenon flos-aquae (DGUC003) resulted in significant inhibition of algal growth on the Aulacoseira ambigua f. spiralis (DGUD001) and Aphanizomenon flos-aquae (DGUC001) (p < 0.01).

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.29-29
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• 2003

Compartmentation of intracellular signaling pathways serves as an important mechanism conferring the specificity of G protein-coupled receptor (GPCR) signaling. In the heart, stimulation of $\beta$$_2$-adrenoceptor ($\beta$$_2$-AR), a prototypical GPCR, activates a tightly localized protein kinase A (PKA) signaling, which regulates substrates at cell surface membranes, bypassing cytosolic target proteins (eg, phospholamban). Although a concurrent activation of $\beta$$_2$-AR-coupled $G_{i}$ proteins has been implicated in the functional compartmentation of PKA signaling, the exact mechanism underlying the restriction of the $\beta$$_2$-AR-PKA pathway remains unclear. In the present study, we demonstrate that phosphatidylinositol 3-kinase (PI3K) plays an essential role in confining the $\beta$$_2$-AR-PKA signaling. Inhibition of PI3K with LY294002 or wortmannin enables $\beta$$_2$-AR-PKA signaling to reach intracellular substrates, as manifested by a robust increase in phosphorylation of phospholamban, and markedly enhances the receptor-mediated positive contractile and relaxant responses in cardiac myocytes. These potentiating effects of PI3K inhibitors are not accompanied by an increase in $\beta$$_2$-AR-induced cAMP formation. Blocking $G_{i}$ or $G_{$\square$$\square$}$ signaling with pertussis toxin or $\beta$ARK-ct, a peptide inhibitor of $G_{$\square$$\square$}$, completely prevents the potentiating effects induced by PI3K inhibition, indicating that the pathway responsible for the functional compartmentation of $\beta$$_2$-AR-PKA siglaling sequentially involves $G_{i}$, $G_{$\square$$\square$}$, and PI3K. Thus, PI3K constitutes a key downstream event of $\beta$$_2$-AR- $G_{i}$ signaling, which confines and negates the concurrent $\beta$$_2$-AR/Gs-mediated PKA signaling.gnaling.

• Korean Journal of Microbiology
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• v.27 no.3
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• pp.310-315
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• 1989

Tabtoxin produced in Pseudomonas syringae pv. tabace irreversibly inhibits its known physiological target, glutamine synthetase so that causes wildfire disease on leaves of host plant. In this study, we examined a rapid and sensitive microbiological method for tabtoxin assay in several media. In minimal A agar medium nd minimal glucose agar medium, growth inhibition zone of Agrobacterium tumefaciens was larger than that of other indicator strain. However, mostly, growth inhibition zone of indicator strains on the minimal glucose agar medium was smaller than that of on the miniaml A agar medium. In complex agar medium, growth inhibithiton zone was not observed in all the tested indicator strains. Pseudomonas syringae pv. tabaci produced more tabtoxin according to the incubation time. When glutamine was added to the minimal glucose agar medium, growth inhkbition zone of Agrobacterium tumefaciens was reduced.

• Journal of Microbiology and Biotechnology
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• v.28 no.12
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• pp.2079-2094
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• 2018

Sunflower trypsin inhibitor (SFTI) is a 14-amino-acid bicyclic peptide that contains a single internal disulfide bond. We initially constructed chimeras of SFTI with N-terminal secretion signals from the Escherichia coli OmpA and Pseudomonas aeruginosa ToxA, but only detected small amounts of protease inhibition resulting from these constructs. A substantially higher degree of protease inhibition was detected from a C-terminal SFTI fusion with E. coli YebF, which radiated more than a centimeter from an individual colony of E. coli using a culture-based inhibitor assay. Inhibitory activity was further improved in YebF-SFTI fusions by the addition of a trypsin cleavage signal immediately upstream of SFTI, and resulted in production of a 14-amino-acid, disulfide-bonded SFTI free in the culture supernatant. To assess the potential of the secreted SFTI to protect the ability of a cytotoxic protein to kill tumor cells, we utilized a tumor-selective form of the Pseudomonas ToxA (OTG-PE38K) alone and expressed as a polycistronic construct with YebF-SFTI in the tumor-targeted Salmonella VNP20009. When we assessed the ability of toxin-containing culture supernatants to kill MDA-MB-468 breast cancer cells, the untreated OTG-PE38K was able to eliminate all detectable tumor cells, while pretreatment with trypsin resulted in the complete loss of anticancer cytotoxicity. However, when OTG-PE38K was co-expressed with YebF-SFTI, cytotoxicity was completely retained in the presence of trypsin. These data demonstrate SFTI chimeras are secreted in a functional form and that co-expression of protease inhibitors with therapeutic proteins by tumor-targeted bacteria has the potential to enhance the activity of therapeutic proteins by suppressing their degradation within a proteolytic environment.

• Microbiology and Biotechnology Letters
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• v.25 no.5
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• pp.448-453
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• 1997

Enzyme activities, production of killer toxin and some functionality of forty seven yeasts isolated from traditional Meju were investigated in culture broth and cell free extracts. Activities of $\alpha$-galactosidase, invertase and inulinase were detected in cell free extracts of 38 strains, 43 strains and 45 strains, respectively and acidic and neutral protease activities also were detected in culture broth of all the strains, $\beta$-Galactosidase activity was detected in cell free extracts of OE-20 and S-14 strains. Killer toxins were produced by OE-12, S-8 (Candida spp.), OE-19 (Zygosaccharomyces spp.) and S-3 (Saccharomyces spp.). Culture broth of OE-23 and S-9 showed 61.3% and 59.2% of antioxidant activity to $\alpha$, $\alpha$-diphenyl-$\beta$-picrylhydrazyl(DPPH), but nitrite-scavenging ability as well as inhibition of tyrosinase and polyphenol oxidase were not appeared in all the strains.

• Applied Biological Chemistry
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• v.33 no.2
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• pp.169-173
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• 1990

The anthraquionone mycotoxin, skyrin, is produced by Penicillium islandicum. DF-100 which was extracted from grapfruit seed extract and is a natural organic complex inhibited the biosynthesis of skyrin by Penicillium islandicum. This study was carried out to determine the potential of DF-100 to support Penicillium islandicum and skyrin production. DF-100 inhibited the growth of the fungus at 750ppm or less and caused complete inhibition of skyrin production at 500ppm or less. DF-100 appears to block the incorporation of emodinathrone into skyrin and an enzymatic step in the skyrin biosynthetic pathway which lies before skyrinanthrone.

• Journal of Applied Biological Chemistry
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• v.60 no.4
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• pp.351-355
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• 2017

Tolaasin, peptide toxin produced by Pseudomonas tolaasii, causes a brown blotch disease on the cultivated mushrooms. Tolaasin peptides form membrane pores and disrupt cellular membrane structure. Molecular actions of tolaasin consist of the aggregation of peptide molecules, binding to the cell membrane, and formation of membrane pores. Therefore, the inhibitions of any of these actions are able to suppress the blotch disease. We have isolated and identified several tolaasin inhibitors (named tolaasin inhibitory factors, TIF) from food additives. TIFs were able to suppress the blotch-formation by the pathogen inoculated to the mushrooms. In this study, TIFs were incubated under various conditions and their activities for the inhibition of tolaasin-induced hemolytic activity were investigated. Since TIFs are unsaturated carbon compounds, they were sensitive to the air exposure and light irradiation. In the anaerobic conditions, TIFs were stable and their activities were decreased by 10% for three months. However, near 90% of TIF activity was suppressed by two weeks in the presence of air and sun light. Temperature did not show any significant effects on the activity of TIF, since storages at 5, 25, $45^{\circ}C$ did not show any difference. Therefore, for the stable storage of TIF compounds, container should be designed to be dark and air-tight.

• Applied Biological Chemistry
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• v.43 no.3
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• pp.190-195
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• 2000

Tolaasin is a peptide toxin produced by Pseudomonas tolaasii and causes a brown blotch disease forming brown, slightly sunken spots and blotches on the cultivated mushrooms. It is a lipodepsipeptide consisting of 18 amino acids and its molecular mass is 1,985 Da. It forms a pore in plasma membranes, resulting in the disruption of membranes of fungal, bacterial, plant, and animal cells as well as mushroom tissue. In order to measure the toxicity of tolaasin, erythrocytes of blood were used to evaluate the tolaasin-induced hemolysis. Hemolytic activity of tolaasin was measured by observing the absorbance change either at 420 nm, representing the release of hemoglobins from red blood cells(RBCs), or at 600 nm, representing the density of residual cells. The hemolytic activity of culture-extract of P. tolaasii increased at early-stationary phase of growth and was maximal at late stationary phase. The hemolytic activity of tolaasin appeared high in the RBCs of dog and rat. The RBCs of rabbit and hen were less susceptible to tolaasin. The effects of various cations were also measured. $Cd^{2+}$ and $La^{3+}$. as well as $Zn^{2+}$ appeared inhibitory to the tolaasin-induced hemolysis. The effects of various anions on tolaasin-induced hemolysis were measured and carbonate showed the greatest inhibition to the hemolysis. However, phosphate stimulated the tolaasin-induced hemolysis and no effects were observed by chloride and nitrate.

• Korean Journal of Microbiology
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• v.55 no.3
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• pp.226-233
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• 2019

Ochratoxin A (OTA) that is one of mycotoxins produced mainly by Aspergillus spp. is a common contaminant of stored grains and poses health hazards to human and livestock. The aim of this study is to explore the ability of isolated bacteria Bacillus subtilis AF13 and Streptomyces shenzhenensis YR226 to inhibit growth and OTA production of 3 ochratoxigenic Aspergillus strains. The antifungal activity against mycelial growth and sporulation of Aspergillus strains was examined by coculture with AF13 and YR226 on potato dextrose agar plate. AF13 and YR226 reduced 77.58 and 78.48% of fungal colony radius, respectively, and both strains inhibited fungal sporulation up to 99% in 10 days of incubation. YR226 also reduced more than 91% of spore germination of 3 fungal strains. When Aspergillus strains were cocultured with AF13 or YR226 in yeast extract sucrose medium, mycelial growth and OTA production decreased in all three fungal strains. In particular, AF13 completely inhibited the mycelial growth of A. alutaceus and inhibited its OTA production by 99%, and YR226 also reduced mycelial growth and toxin production up to 99%, respectively. Antimicrobial substances produced by AF13 and YR226 included siderophore, chitinase, protease, ${\beta}$-1,3-glucanase and biosurfactant. These results suggest that AF13 and YR226 can be used in a biological method to prevent valuable crops against mycotoxigenic fungi, and therefore decrease economic damage in agriculture and feed industry.

• Proceedings of the Korean Society of Food Science and Nutrition Conference
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• 2004.11a
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• pp.110-115
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• 2004

The immature fruits of Poncirus trifoliata L. or Ponciri fructus (PF), well known as 'Jisil' in Korea, have been used against allergic diseases for generations, and still occupy an important place in traditional Oriental medicine. Anti-allergic effects of this fruit have been investigated in a few experimental models. Immunoglobulin E (IgE) is the principal immunoglobulin involved in immediate hypersensitivities and chronic allergic diseases. The effect of an aqueous extract of PF on in vivo and in vitro IgE production was investigated. PF dose-dependently inhibited the active systemic anaphylaxis and serum IgE production induced by immunization with ovalbumin, Bordetelia pertussis toxin and aluminum hydroxide gel. PF strongly inhibited interleukin 4 (IL-4)-dependent IgE production by lipopolysaccharide-stimulated murine whole spleen cells. In the case of U266 human IgE-bearing B cells, Ponciri fructus also showed an inhibitory effect on the IgE production. On the other hand, mast cell hyperplasia can be causally related with chronic inflammation. Stem cell factor (SCF), the ligand of the c-kit protooncogene product, is a major regulator and ohernoattractant of mast cells. Ponciri fiuctus (1 mg/mL) significantly inhibited the SCF-induced migration of rat peritoneal mast cells (RPMCs). RPMCs exposed to SCF (50 ng/mL) resulted in a drastic shape change with a polarized morphology while the cells exposed to Ponciri fructus (1 mg/mL) remained resting, with little or no shape alteration. The drastic morphological alteration and distribution of polymerized actin were blocked by pretreatment with Ponciri fructus. In addition, Ponciri fructus inhibited both TNF-alpha and IL-6 secretion from RPMCs stimulated with SCF. These results suggest that Ponciri fructus has an anti-allergic activity by inhibition of IgE production from B cells. These findings also provide evidence that Ponciri fructu inhibits chemotactic response and inflammatory cytokines secretion to SCF in mast cells.