• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1368-1376
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• 2005

Pseudomonas aeruginosa produces a variety of bacteriocidal substances including pyocins that are active against the same species, but their physiological roles are relatively unknown. Here, we profiled the bacteriocidal activities in the culture supernatants of various P. aeruginosa isolates and describe the competitive growth advantages of strains PAO1 and PA14 over some strains including PAK, which are sensitive to their bacteriocidal activities. These findings suggest that the factors governing the production of pyocins and the resistance to them play important roles in controlling P. aeruginosa populations in its local environments.

• Food Science and Biotechnology
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• v.17 no.5
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• pp.1074-1078
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• 2008

To investigate the antiviral activity of marine algae against fish pathogenic viruses, which are often the causes of viral disease in aquaculture, the 80% methanolic extracts of 21 species collected from the coast of Korea were screened for their in vitro antiviral activities on infectious hematopoietic necrosis virus (IHNV) and infectious pancreatic necrosis virus (IPNV), using a flounder spleen (FSP) cell-line. Among them, Monostroma nitidum (10 ${\mu}g/mL$) exhibited the strongest inactivation on IHNV, showing a 2 log reduced virus titre as compared to the control in the determination of direct virucidal activity. In addition, Polysiphonia morrowii (100 ${\mu}g/mL$) remarkably reduced the virus titres of treated cells by 2-2.5 log, for both IHNV and IPNV, in the determination of cellular protective activity, implying the existence of substances that may modulate innate host defense mechanisms against viral infections. These results reveal that some marine algae could be promising candidates as sources of antiviral agents or as health-promoting feeds for aquaculture.

• Toxicological Research
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• v.26 no.4
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• pp.301-313
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• 2010

Growth promoters including hormonal substances and antibiotics are used legally and illegally in food producing animals for the growth promotion of livestock animals. Hormonal substances still under debate in terms of their human health impacts are estradiol-$17\beta$, progesterone, testosterone, zeranol, trenbolone, and melengestrol acetate (MGA). Many of the risk assessment results of natural steroid hormones have presented negligible impacts when they are used under good veterinary practices. For synthetic hormonelike substances, ADIs and MRLs have been established for food safety along with the approval of animal treatment. Small amounts of antibiotics added to feedstuff present growth promotion effects via the prevention of infectious diseases at doses lower than therapeutic dose. The induction of antimicrobial resistant bacteria and the disruption of normal human intestinal flora are major concerns in terms of human health impact. Regulatory guidance such as ADIs and MRLs fully reflect the impact on human gastrointestinal microflora. However, before deciding on any risk management options, risk assessments of antimicrobial resistance require large-scale evidence regarding the relationship between antimicrobial use in food-producing animals and the occurrence of antimicrobial resistance in human pathogens. In this article, the risk profiles of hormonal and antibacterial growth promoters are provided based on recent toxicity and human exposure information, and recommendations for risk management to prevent human health impacts by the use of growth promoters are also presented.

• Journal of environmental and Sanitary engineering
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• v.6 no.1
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• pp.7-25
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• 1991

Until now, pure drinking water grnerally menas the water without taste, odor, general bacteria, coliform, and other exotic substance. Such a definition has been changing recently due to the finding of numerous other inorganic and organic substances unknown to us. 10 years ago, major causes of death were infectious agents and parasites contained in water, but recently, it has become apparent that some substances contained in drinking water cause cancer and heart diseases. We must drink about 2L of water everyday in order to maintain healthy condition. Waters used for drinking include tap water, well water, spring water, filtered water, etc., but the quality of drinking water has more polluted due to the industrial development and population increase. For example, industrial waste waters from industrial plants pollute the water supply sources ; toxic substances contained in the waste waters pollute the ground water sources by penetrating the geological strata, and municipal, livestock, public building waste waters also pollute the water supply sources. Sometimes, the polluted surface waters were announced to be polluted by various kinds of orgainc substance, and it is reported that the pollution of ground water by orga nic substances has few in number but high in its concectration comparing with those of surface water. As the water quality pollution level increases, so the amount of disinfectant also increase. For example, chlorine solution, one of widely used disinfectants, creates trihalomethane(THM), a carcinogen, and halogen compounds. According to Oliver, through chlorine disinfection process, humine substance and chlorine create bolatile organic halide and nonvolatile organic halide by chemical reaction. There are tens or hundreds filtering devices, but filtering principles and maintenance metjhods are different, so their efficiency tests are needed. According to Smith, the effeciency tests aginst over 30 Ameican filtering devices show that 10 devices can remove 85% of volatile organics and further studies on filtered waters are underway. In consideration of important impacts of polluted drinking water on national health, authors studied the state of water quality pollution against tap water used as drinking water, filtration device passed water, ground water, and conserved drinking water ; tested the efficiency of filtration devices for tap water ; tried to sep up the detection method by using ion chromatography based on negative ion and positive ion by using single column, and attemped the simple filtration method for general households.

• Journal of Microbiology and Biotechnology
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• v.18 no.1
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• pp.28-34
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• 2008

Biofilm formation in association with the intercellular adhesion (icaADBC) gene cluster is a serious problem in nosocomial infections of Staphylococcus aureus. In all 112 S. aureus strains tested, the ica genes were present, and none of these strains formed biofilms. The biofilm formation is known to be changeable by environmental factors. We have found about 30% of phase variation in these strains with treatment of tetracycline, pristinamycin, and natrium chloride. However, this phenotype disappeared without these substances. Therefore, we have constructed stable biofilm-producing variants through a passage culture method. To explain the mechanism of this variation, nucleotide changes of ica genes were tested in strain S. aureus 483 and the biofilm-producing variants. No differences of DNA sequence in ica genes were found between the strains. Additionally, molecular analysis of three regulatory genes, the accessory gene regulator (agr) and the staphylococcal accessory regulator (sarA), and in addition, alternative transcription factor ${\sigma}^B$ (sigB), was performed. The data of Northern blot and complementation showed that SigB plays an important role for this biofilm variation in S. aureus 483 and the biofilm-producing variants. Sequence analysis of the sigB operon indicated three point mutations in the rsbU gene, especially in the stop codon, and two point mutations in the rsbW gene. This study shows that this variation of biofilm formation in S. aureus is deduced by the role of sigB, not agr and sarA.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.1
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• pp.63-77
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• 2019

Traditional wastewater research mainly focuses on 1) estimating the amount of waste entering sewage treatment facilities, 2) evaluating the treatment efficiency of sewage facilities, 3) investigating the role of sewage treatment effluent as a point source, and 4) designing and managing sewage treatment facilities. However, since wastewater contains a variety of chemical and biological substances due to the discharge of human excreta and material used for daily living into it, the collective constituents of wastewater are likely a reflection of a community's status. Wastewater-based epidemiology (WBE), an emerging and promising field of study that involves the analysis of substances in wastewater, can be applied to monitor the state of a defined community. WBE provides opportunities for exploiting indicators in wastewater to fulfill various objectives. The data analyzed under WBE are those pertaining to selected natural and anthropogenic substances in wastewater that are a result of the discharge of metabolic excreta, illicit or legal drugs, and infectious pathogens into the wastewater. This paper reviews recent progress in WBE and addresses current challenges in the field. It primarily discusses several representative applications including the investigation of drug consumption across different communities and the management of community disease and health. Finally, it summarizes established indicators for WBE.

• Clinical and Experimental Pediatrics
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• v.48 no.7
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• pp.691-695
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• 2005

There is scientific evidence that administration of probiotics is effective in the treatment of acute infectious diarrhea in children and the prevention of antibiotic associated diarrhea and nosocomial/community acquired diarrhea. Probiotics prevent relapse of recurrent pouchitis and decrease the initial onset of pouchitis in ulcerative colitis. Probiotic organisms suppress growth of pathogens as well as their epithelial attachment and/or invasion either directly by secreting antimicrobial substances or by stimulating host expression of protective molecules. Additionally, probiotics enhance mucosal barrier function and can stimulate host production of immunosuppressive molecules that downregulate inflammatory responses or allergic immune response. Mechanisms of action explain therapeutic effects and randomized controlled trials are warranted before recommendations for therapeutic or preventive use can be given.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1998.11a
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• pp.189-189
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• 1998

Tissue factor (TF) is a cell surface receptor of coagulation factor Ⅶ and is the principal initiator of the vertebrate coagulation cascade. TF is found in high levels in some organs such as brain, lung and placenta, whereas blood monocytes, endothelial cells contain only trivial amount of TF when quiescent, and is stimulated to synthesize TF by infections or vascular lesions. TF is reported to be found in high levels in atherosclerotic plaques, cancer cells. TF activation in various cells in many infectious or immunologic diseases tells us the physiologic importance of TF. We screened many edible vegetables for TF inhibitor, by measuring the prothrombin time to detect the TF activity, and we picked Aster scaber to isolate the TF inhibitory substance. Aster scaber showed two kinds of anti thrombotic activity, one is TF inhibition and the other is elongation of plasma recalcification time. The anti thrombotic substances were found to be saponins which has echinocystic acid as aglycone.

• Journal of Environmental Science International
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• v.33 no.3
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• pp.205-215
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• 2024

Antibiotics are substances produced by microorganisms that kill or inhibit and are essential for infectious diseases management. This study aimed to provide basic data for overcoming antibiotic resistance in the marine bacterium LJ-18. The API 20NE and API 50CH kits were used to identify this microorganism. Morphological, physiological, and biochemical properties were investigated using MacFaddin's manuals. Subsequently, isolated LJ-18 was found to belong to a genus of Streptomyces that forms mycelia. LJ-18 also grew well at 28-32℃ on modified Bennett's agar. To isolate and purify the antibacterial compound, LJ-18 culture was divided into ethyl acetate and distilled water fractions. Considerable antimicrobial activity against various pathogenic microorganisms, including methicillin-resistant Staphylococcus aureus (MRSA), was confirmed in the C₁₈ ODS open column fractions. Peak 2 compound was obtained using reversed-phase HPLC. As a result, this compound had a significant antimicrobial activity against various pathogenic microorganisms. In particular, it showed strong activity against MRSA, Mycobacterium smegmatis, Bacillus subtilis, Bacillus cereus, and Staphylococcus aureus.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.40-44
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• 2003

Soil-borne infectious disease including Pythium aphanidermatum and Rhizoctonia solani causes severe damage to plants, such as cucumber. This soil-borne infectious disease was not controlled effectively by chemical pesticide. Since these diseases spread through the soil, chemical agents are usually ineffective. Instead, biological control, including antagonistic microbe can be used as a preferred control method. An efficient method was developed to select an antagonistic strain to be used as a biological control agent strain. In this new method, surface tension reduction potential of an isolate was included in the ‘decision factor’ in addition to the other factors, such as growth rate, and pathogen inhibition rate. Considering these 3 decision factors by a statistical method, an isolate from soil was selected and was identified as Bacillus sp. GB16. In the pot test, this strain showed the best performance among the isolated strains. The lowest disease incidence rate and fastest seed growth was observed when Bacillus sp. GB16 was used. Therefore this strain was considered as plant growth promoting rhizobacteria (PGPR). The action of surface tension reducing component was deduced as the enhancement of wetting, spreading, and residing of antagonistic strain in the rhizosphere. This result showed that new selection method was significantly effective in selecting the best antagonistic strain for biological control of soil-borne infectious plant pathogen. The antifungal substances against P. aphanidermatum and R. solani were partially purified from the culture filtrates of Bacillus sp. GB16. In this study, lipopeptide possessing antifungal activity was isolated from Bacillus sp. GB16 cultures by various purification procedures and was identified as a surfactin-like lipopeptide based on the Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), high performance liquid chromatography mass spectroscopy (HPLC-MS), and quadrupole time-of-flight (Q-TOF) ESI-MS/MS data. The lipopeptide, named GB16-BS, completely inhibited the growth of Pythium aphanidermatum, Rhizoctonia solani, Penicillium sp., and Botrytis cineria at concentrations of 10 and 50 mg/L, respectively. A novel method to prevent the foaming and to provide oxygen was developed. During the production of surface active agent, such as lipopeptide (surfactin), large amount of foam was produced by aeration. This resulted in the carryover of cells to the outside of the fermentor, which leads to the significant loss of cells. Instead of using cell-toxic antifoaming agents, low amount of hydrogen peroxide was added. Catalase produced by cells converted hydrogen peroxide into oxygen and water. Also addition of corn oil as an oxygen vector as well as antifoaming agent was attempted. In addition, Ca-stearate, a metal soap, was added to enhance the antifoam activity of com oil. These methods could prevent the foaming significantly and maintained high dissolved oxygen in spite of lower aeration and agitation. Using these methods, high cell density, could be achieved with increased lipopeptide productivity. In conclusion to produce an effective biological control agent for soil-borne infectious disease, following strategies were attempted i) effective screening of antagonist by including surface tension as an important decision factor ii) identification of antifungal compound produced from the isolated strain iii) novel oxygenation by $H_2O_2-catalase$ with vegetable oil for antifungal lipopeptide production.