• Journal of Microbiology and Biotechnology
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• v.20 no.2
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• pp.271-280
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• 2010

Vibrio alginolyticus, a Gram-negative marine bacterium, is one of the causative agents of fish vibriosis. Its virulence factors and pathogenesis mechanism are barely known, except for some extracellular products (ECPs) that are known to be regulated by quorum sensing system. Therefore, the present study used a microarray to analyze the transcription profiles of the wild-type V. alginolyticus and a deletion mutant of luxO, the pivotal regulator in Vibrio quorum sensing systems, which resulted in the identification of a putative virulence factor, MviN. Quantitative real-time reverse transcription PCR confirmed that the transcription of mviN was upregulated in the luxO mutant when compared with wild-type, and down regulated in a luxO-con complemented strain. Furthermore, Western blotting indicated that MviN was greatly induced during the late-exponential and stationary phases of growth, indicating that the expression of MviN was cell-density dependent and quorum sensing regulated in V. alginolyticus. Meanwhile, the mviN null mutant displayed a much slower growth rate than the wild type, signifying the essential role of MviN in V. alginolyticus. Western blotting also revealed that MviN was present as an extracellular protein in V. alginolyticus. When epithelioma papulosum cyprini (EPC) cells were treated with the ECPs of the mviN mutant, no cytotoxicity was observed, whereas EPC cells treated with the wild type exhibited pathological changes, which increased with the ECPs concentration and treatment time. Therefore, the results demonstrated that MviN is a LuxO-regulated ECPs component and involved in the pathogenicity of V. alginolyticus.

• Toxicological Research
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• v.20 no.3
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• pp.179-185
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• 2004

Helicobacter pylori (H. pylori) infects more than half of the people in the world as a major microbe to cause most of gastric diseases. Recently, cytotoxin associated-antigen A (CagA) is believed as one of the most important virulence factors of H. pylori. Molecular toxicological pathway of CagA is necessary to investigate for understanding the pathological and toxicological aspects of H. pylori, since this virulence protein harasses intercellular processes of host cells to get profit for the survival of H. pylori. CagA is coded from cag pathogenicity island (cag PAI) and translocated into host cells by Type 4 secretion system (TFSS). Tyrosine phosphorylation of CagA targets Src homology 2-containing phosphotyrosine phosphatase (SHP-2) to form a CagA-SHP-2 complex. This complex depends on the similarity of sequence between EPIYA motif and Src homology 2 domain (SH2 domain) of CagA. The generation of growth factors is an essential role of CagA in protecting and healing gastric mucosa for the survival of H. pylori. On the other hand, the activation of IL-8 by CagA induces neutrophils generating inflammation and free radicals. Indeed, free radicals are well known carcinogen to induce DNA damage. In addition, the transduction of mitogen-activation signal by CagA is one of the interesting features to understand how to cause cancer. The relationship between cancer and inflammation with CagA was mainly discussed in this review.

• The Plant Pathology Journal
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• v.33 no.3
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• pp.249-263
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• 2017

This study aims to examine the potential reasons for the current prevalence of the fusarium wilt in the oriental melon. Twenty-seven Fusarium isolates obtained from oriental melon greenhouses in 2010-2011 were identified morphologically and by analysis of elongation factor-1 alpha gene (EF-$1{\alpha}$) and internal transcribed spacer (ITS) rDNA sequences as 6 Fusarium species (8 isolates of F. oxysporum, 8 F. commune, 5 F. proliferatum, 3 F. equiseti, 2 F. delphinoides, and 1 F. andiyazi), which were classified as same into 6 EF-$1{\alpha}$ sequence-based phylogenetic clades. Pathogenicity of the Fusarium isolates on the oriental melon was highest in F. proliferatum, next in F. oxysporum and F. andiyazi, and lowest in the other Fusarium species tested, suggesting F. proliferatum and F. oxysporum were major pathogens of the oriental melon, inducing stem rots and vascular wilts, respectively. Oriental melon and watermelon were more susceptible to F. oxysporum than shintosa and cucumber; and cucumber was most, oriental melon and watermelon, medially, and shintosa was least susceptible to F. proliferatum, whose virulence varied among and within their phylogenetic subclades. Severe root-knot galls were formed on all the crops infected with Meloidogyne incognita; however, little indication of vascular wilts or stem and/or root rots was shown by the nematode infection. These results suggest the current fungal disease in the oriental melon may be rarely due to virulence changes of the fusarium wilt pathogen and the direct cause of the severe root-knot nematode infection, but may be potentially from other Fusarium pathogen infection that produces seemingly wilting caused by severe stem rotting.

• Journal of Microbiology and Biotechnology
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• v.27 no.2
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• pp.262-270
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• 2017

Yersinia enterocolitica is a well-known foodborne pathogen causing gastrointestinal infections worldwide. The strain Y. enterocolitica FORC_002 was isolated from the gill of flatfish (plaice) and its genome was sequenced. The genomic DNA consists of 4,837,317 bp with a GC content of 47.1%, and is predicted to contain 4,221 open reading frames, 81 tRNA genes, and 26 rRNA genes. Interestingly, genomic analysis revealed pathogenesis and host immune evasion-associated genes encoding guanylate cyclase (Yst), invasin (Ail and Inv), outer membrane protein (Yops), autotransporter adhesin A (YadA), RTX-like toxins, and a type III secretion system. In particular, guanylate cyclase is a heat-stable enterotoxin causing Yersinia-associated diarrhea, and RTX-like toxins are responsible for attachment to integrin on the target cell for cytotoxic action. This genome can be used to identify virulence factors that can be applied for the development of novel biomarkers for the rapid detection of this pathogen in foods.

• Animal Bioscience
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• v.34 no.4
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• pp.734-742
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• 2021

Objective: The present study aimed to investigate the occurrence and species of coagulase-positive staphylococci (CoPS) and coagulase-negative staphylococci (CoNS) in retail pork meat samples collected during nationwide monitoring. The staphylococcal isolates were characterized for antimicrobial and zinc chloride resistance and enterotoxigenic potential. Methods: A total of 260 pre-packaged pork meat samples were collected from 35 retail markets in 8 provinces in Korea for isolation of staphylococci. Antimicrobial and zinc chloride resistance phenotypes, and genes associated with the resistance phenotypes were determined on the isolates. Furthermore, the presence and distribution of 19 staphylococcal enterotoxin (SE) genes and enterotoxin-like genes among the pork-associated staphylococci were determined by multiplex polymerase chain reaction-based assays using the specific primer sets. Results: A total of 29 staphylococcal strains (29/260, 11.1%) were isolated from samples of retail pork meat, 24 (83%) of which were CoNS. The four CoNS species identified were S. saprophyticus (n = 16, 55%), S. sciuri (n = 3, 10%), S. warneri (n = 3, 10%), and S. epidermidis (n = 2, 7%). Among the 29 isolates, four methicillin-resistant CoNS (MR-CoNS; three S. sciuri and one S. epidermidis) and one methicillin-resistant CoPS (MR-CoPS; one S. aureus) were identified. In addition, a relatively high level of tetracycline (TET) resistance (52%) was confirmed in CoNS, along with a predominant distribution of tet(K). The most prevalent SEs were sep (45%), and sen (28%), which were carried by 81% of S. saprophyticus. Conclusion: These findings suggest that CoNS, especially S. saprophyticus strains, in raw pork meat could be a potential risk factor for staphylococcal food poisoning (SFP), and therefore, requires further investigation to elucidate the role of SEls in SFP and virulence of the pathogen. Our results also suggest that CoNS from raw pork meat may act as a source for transmission of antimicrobial resistance genes such as staphylococcal cassette chromosome mec and tet(K).

• Korean Journal of Agricultural Science
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• v.50 no.2
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• pp.283-289
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• 2023

Erwinia amylovora , which causes fire blight disease on apple and pear trees, is one of the most important phytopathogens because of its devastating impact. Currently, the only way to effectively control fire blight disease is through the use of antibiotics such as streptomycin, kasugamycin, or oxytetracycline. However, problems with the occurrence of resistant strains due to the overuse of antibiotics are constantly being raised. It is therefore necessary to develop novel disease control methods through an advanced understanding of the pathogenesis mechanism of E. amylovora . To better understand the pathogenesis of E. amylovora , we investigated unknown virulence factors by random mutagenesis and screening. Random mutants were generated by Tn5 transposon insertion, and the pathogenicity of the mutants was assessed by inoculation of the mutants on apple fruitlets. A total of 17 avirulent mutants were found through screening of 960 random mutants. Among them, 14 mutants were already reported as non-pathogenic strains, while three mutants, TS3128_M2899 (ΔSUFU ), TS3128_M2939 (ΔwcaG ), and TS3128_M3747 (ΔrecB ), were not reported. Further study of the association between E. amylovora pathogenicity and these 3 novel genes may provide new insight into the development of control methods for fire blight disease.

• Journal of Food Hygiene and Safety
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• v.35 no.3
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• pp.271-278
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• 2020

Enterotoxigenic Escherichia coli is one of the major causative infectious agents of diarrhea in newborn and post-weaning pigs and leads to a large economic loss worldwide. However, there is limited information on the distribution and characterization of virulence genes in E. coli isolated from diarrheic piglets, which also applies to the current status of pig farms in Korea. To investigate the prevalence and characterization of virulence genes in E. coli related to diarrhea in piglets, the rectal swab samples of diarrheic piglets (aged 2 d to 6 w) were collected from 163 farms between 2013 and 2016. Five to 10 individual swab samples from the same farm were pooled and cultured on MacConkey agar plates, and E. coli were identified using the API 32E system. Three sets of multiplex PCRs were used to detect 13 E. coli virulence genes. As a result, a total of 172 E. coli isolates encoding one or more of the virulence genes were identified. Among them, the prevalence of individual virulence gene was as follows, (1) fimbrial adhesins (43.0%): F4 (16.9%), F5 (4.1%), F6 (1.7%), F18 (21.5%), and F41 (3.5%); (2) toxins (90.1%): LT (19.2%), STa (20.9%), STb (25.6%), Stx2e (15.1%), EAST1 (48.3%); and (3) non-fimbrial adhesin (19.6%): EAE (14.0%), AIDA-1 (11.6%) and PAA (8.7%), respectively. Taken together, various pathotypes and virotypes of E. coli were identified in diarrheic piglets. These results suggest a broad array of virulence genes is associated with coliform diarrhea in piglets in Korea.

• Journal of Photoscience
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• v.9 no.2
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• pp.323-325
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• 2002

Bacillus Anthracis is the causative agent of anthrax. The major virulence factors are a poly-D glutamic acid capsule and three-protein component exotoxin, which is collectively known as anthrax toxin, protective antigen (PA, 83 kDa), lethal factor (LF, 90 kDa), and edema factor (EF, 89 kDa). These three proteins individually have no known toxic activities, but in combination with PA form two toxins (lethal toxin and edema toxin), causing different pathogenic responses in animals and cultured cells. However, it remains to be elucidated for pathogenic mechanism of anthrax toxin. In this study, we constructed toxin component in bacterial overexpression system and purified the native toxin from Bacillus anthracis delta sterne F32 using FPLC system. Recombinant toxin showed high homogeneity and rapid purification processes. Also, this recombinant toxin was comparable to B. anthracis native toxin in terms of cytotoxic effects on cultured cell lines.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.107.1-107
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• 2003

The fermentation process and subsequent processing determine the efficacy of a bioherbicide propagule. Large batches of biomass of the mycoherbicide agent for white clover, Sclerotium sp.(BWC98-105) was produced in simple liquid fermentator in 5 gallons vessels(Model No. 8087, Dabo Inc., Korea) with oxygen supply(DPH16000, FineTech Inc., Korea) simulating industrial conditions by utilizing commercially available, inexpensive ingredients (10 ％ rice bran), The maximum biomass yield of Sclerotium sp.(BWC98-105) was obtained after 5 days of air pumped incubation at room temperature condition(22-28$^{\circ}C$). By using this simple facility, it could get fragmented or proliferated greatly and attained maximum mycelia biomass. The biomass of mycoherbicide agent consisted of hyphae devoid of spores. Biomass mycelia of the fungus 99％ survival at room temperature after 2 me. A thorough understanding of the effects of fermentation and formulation on viability and virulence is required to guide these processes. After an economical yield level of bioherbicide propagule has been achieved in a fermentation process, formulation becomes a critical factor which influences product efficacy. Because the fermentation must be stopped at a point when virulence/viability are optimum, the live bioherbicide propagule must be stabilized, formulated, and packaged.

• The Journal of the Korean Society for Microbiology
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• v.22 no.1
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• pp.71-78
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• 1987

In order to determine the virulence properties of eleven strains of Sh. flexneri isolated from diarrheal patients the congo red test, the $Ser{\acute{e}}ny$ test, the HeLa cell invasion test and electrophoresis of plasmids were carried out. The results were summarized as follows. 1. Virulent strains were not determined by the result of Congo red absorption test. 2. Virulent strains showed positive reaction by the Sereny test and the HeLa cells invasion, but avirulent strains revealed negative reaction at those tests. 3. The temperature condition of bacterial growth was a factor of virulent expression. 4. Virulent strains were mostly possessed of a 130.3 Mdal plasmid, but avirulent strains were not.