• The Plant Pathology Journal
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• v.29 no.4
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• pp.364-373
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• 2013

It has been known that most regulation of pathogenicity factor (rpf ) genes in xanthomonads regulates virulence in response to the diffusible signal factor, DSF. Although many rpf genes have been functionally characterized, the function of rpfE is still unknown. We cloned the rpfE gene from a Xanthomonas oryzae pv. oryzae (Xoo) Korean race KACC10859 and generated mutant strains to elucidate the role of RpfE with respect to the rpf system. Through experiments using the rpfE-deficient mutant strain, we found that mutation in rpfE gene in Xoo reduced virulence, swarm motility, and production of virulence factors such as cellulase and extracellular polysaccharide. Disease progress by the rpfE-deficient mutant strain was significantly slowed compared to disease progress by the wild type and the number of the rpfE-deficient mutant strain was lower than that of the wild type in the early phase of infection in the inoculated rice leaf. The rpfE mutant strain was unable to utilize sucrose or xylose as carbon sources efficiently in culture. The mutation in rpfE, however, did not affect DSF synthesis. Our results suggest that the rpfE gene regulates the virulence of Xoo under different nutrient conditions without change of DSF production.

• Biomedical Science Letters
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• v.21 no.4
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• pp.233-240
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• 2015

Some virulence proteins of Helicobacter pylori, such as vacuolating cytotoxic protein A (VacA) and cytotoxin-associated gene protein A (CagA) have been reported to be causative agents of various gastric diseases including chronic gastritis, gastric ulcer or gastric adenocarcinoma. The expression level of these virulence proteins can be regulated when H. pylori is exposed to the antibacterial agent, cyanidin 3-O-glucoside (C3G) as previously reported. In this study, we analyzed the quantitative change of various virulence proteins including CagA and VacA by C3G treatment. We used 2-dimensional electrophoresis (2-DE) to analyze the quantitative change of representative ten proteome components of H. pylori 60190 ($VacA^+/CagA^+$; standard strain of Eastern type). After 2-DE analysis, spot intensities were analyzed using ImageMaster$^{TM}$ 2-DE Platinum software then each spot was identified using matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) or peptide sequencing using Finnigan LCQ ion trap mass spectrometer (LC-MS/MS). Next, we selected major virulence proteins of H. pylori among quantitatively meaningful ten spots and confirmed the 2-DE results by Western blot analysis. These results suggest that cyanidin 3-O-glucoside can modulate a variety of H. pylori pathogenic determinants.

• International Journal of Oral Biology
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• v.43 no.4
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• pp.201-207
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• 2018

Porphyromonas gingivalis is among the major etiological pathogens of chronic periodontitis. The virulence mechanisms of P. gingivalis is yet to be identified as its activity is largely unknown in actual disease process. The purpose of this study is to identify antigens of P. gingivalis expressed only in patients with chronic periodontitis using a unique immunoscreening technique. Change Mediated Antigen Technology (CMAT), an antibody-based screening technique, was used to identify virulence-associated proteins of P. gingivalis that are expressed only during infection stage in patients having chronic periodontitis. Out of 13,000 recombinant clones screened, 22 tested positive for reproducible reactivity with rabbit hyperimmune anti-sera prepared against dental plaque samples acquired from periodontitis patients. The DNA sequences of these 18 genes were determined. CMAT-identified protein antigens of P. gingivalis included proteins involved in energy metabolism and biosynthesis, heme and iron binding, drug resistance, specific enzyme activities, and unknown functions. Further analysis of these genes could result in a novel insight into the virulence mechanisms of P. gingivalis.

• Biomedical Science Letters
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• v.24 no.3
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• pp.183-195
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• 2018

Cryptococcosis, which is caused by the Cryptococcus species complex (including Cryptococcus neoformans and Cryptococcus gattii), is well known as one of the most important medical problems. However, the of the Cryptococcus species complex is still limited to pneumonia and meningitis. In particular, the differences in virulence among the five major serotypes of the Cryptococcus species complex are not fully understood. To elucidate the virulence of the Cryptococcus species complex when it is disseminated hematogenously, rats were infected by different strains of the Cryptococcus species serotype, and their histopathological characteristics were compared after infection. The cumulative mortality ratio of rats infected with serotype B strain was slightly higher than in the other experimental groups. In addition, the average recovery of the Cryptococcus species complex from rats infected with serotype B strain was significantly higher than in the other groups in almost all organ samples except spleen. The recovery of the Cryptococcus species complex was associated with the severity of histopathological lesions, including bleeding, inflammation, and tissue damage in all organs. In rats infected with serotype B strain, the virulence was the most severe, especially in the lungs and liver. These results indicate that the pathophysiology of the Cryptococcus species complex infection differs according to serotype.

• Journal of fish pathology
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• v.31 no.1
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• pp.1-8
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• 2018

Causative agent of infectious hematopoietic necrosis (IHN) belonging to genus Novirhabdovirus (Rhabdoviridae). Economic losses caused by IHNV are serious in mainly Oncorhynchus spp. including rainbow trout O. mykiss and Atrantic salmon Salmo salar. IHNV was initially found by endemic presence in U.S. West Coast for sockeye salmon fry O. nerka and chinook salmon fry O. tshawytscha in the 1950s, and it has spread to Japan, Korea and Taiwan in the 1970s, and also to Italy and France in the 1990s. Currently, IHNV is detectable in many parts of the world, including Russia and South America. Mortality due to IHNV infection in fish with ${\leq}0.5g$ of body weight reaches 60% to 100%, while the mortality reduces by fish growing. In recent years, onset of IHNV infection has increased also in fish with large sizes. Here, we introduce molecular epidemiology and virulence changes of IHNV in East Asia, furthermore, we discuss on future prospects in IHNV researches.

• Journal of Microbiology and Biotechnology
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• v.33 no.2
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• pp.167-179
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• 2023

The rifampicin-resistant strain E9-302 of Edwardsiella ictaluri strain 669 (WT) was generated by continuous passage on BHI agar plates containing increasing concentrations of rifampicin. E9-302 was attenuated significantly by 119 times to zebrafish Danio rerio compared to WT in terms of the 50% lethal dose (LD₅₀). Zebrafish vaccinated with E9-302 via intraperitoneal (IP) injection at a dose of 1 × 10³ CFU/fish had relative percentage survival (RPS) rates of 85.7% when challenged with wild-type E. ictaluri via IP 14 days post-vaccination (dpv). After 14 days of primary vaccination with E9-302 via immersion (IM) at a dose of 4 × 10⁷ CFU/ml, a booster IM vaccination with E9-302 at a dose of 2 × 10⁷ CFU/ml exhibited 65.2% RPS against challenge with wild-type E. ictaluri via IP 7 days later. These results indicated that the rifampicin-resistant attenuated strain E9-302 had potential as a live vaccine against E. ictaluri infection. A previously unreported amino acid site change at position 142 of the RNA polymerase (RNAP) β subunit encoded by the gene rpoB associated with rifampicin resistance was identified. Analysis of the whole-genome sequencing results revealed multiple missense mutations in the virulence-related genes esrB and sspH2 in E9-302 compared with WT, and a 189 bp mismatch in one gene, whose coding product was highly homologous to glycosyltransferase family 39 protein. This study preliminarily explored the molecular mechanism underlying the virulence attenuation of rifampicin-resistant strain E9-302 and provided a new target for the subsequent study of the pathogenic mechanism of E. ictaluri.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.4
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• pp.253-260
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• 2000

The virulence(vir) genes in Ti plasmid at Agrobacterium tumefaciens are expressed by a phenolic compound synthesized at plant wound site. The vir genes inducing abilities of 8 phenolic compounds were tested using three wild type strains of A. tumefaciens. It was also investigated how the levels of vir gene expression among the strains tested could be related to the kinds of specific phenolic compounds. Five phenolic compounds like as 4-hydroxyacetophenone, phenol, catechol, resorcinol, and vanillin had exhibited a strong effect on the vir gene expression of A. tumefaciens MW102 whereas they did not be either non-functional or weakly inducible to the vir gene expression of other strains i.e. A. tumefaciens MW105 and MW108. Furthermore, the vir gene of A. tumefaciens MW102 was lowly expressed by acetosyringone that exposed an strong effect on the vir gene induction of other two strains. Thus, it appeared that the vir gene inducing abilities were differed by the kinds of phenolic compounds and Ti plasmids. In conclusion, we suppose that a change in vir gene inducing ability could be resulted from a difference of sensor protein expressed by vir A gene.

• Journal of fish pathology
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• v.9 no.2
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• pp.137-145
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• 1996

A specific disease syndrome, which led to massive mortality on larve of rockfish(Sebastes schlegeli) in marine hatcheries at Chungnam area during the period 1995~1996 was studied. The causative agent isolated from the diseased or dead larvae was identified as Vibrio ordalii on the basis of biochemical and biological characteristics. In the experimental challenges aganist 0 and 1 summer fish conducted at two different temperatures as $18^{\circ}C$ and $25^{\circ}C$, Vibrio ordalii showed higher virulence to no summer fish at $18^{\circ}C$ than 1-summer fish at $25^{\circ}C$. These results were consistent to field data obtained during epizootic outbreaks in the farms. Moribund and died larvae presented telangiectasis of secondary gill lamella and brain, dissecting of respiratory epithelium, atrophy of hepatic cells and necrosis of kidney associated with the presence of the bacteria. But the digestive tissue of these fish showed no significant change.

• Restorative Dentistry and Endodontics
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• v.40 no.4
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• pp.306-313
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• 2015

Objectives: Molecular mechanism of the pathogenicity of Enterococcus faecalis (E. faecalis), a suspected endodontic pathogen, has not yet been adequately elucidated due to limited information on its virulence factors. Here we report the identification of in vivo expressed antigens of E. faecalis by using a novel immunoscreening technique called change-mediated antigen technology (CMAT) and an experimental animal model of endodontic infection. Materials and Methods: Among 4,500 E. coli recombinant clones screened, 19 positive clones reacted reproducibly with hyperimmune sera obtained from rabbits immunized with E. faecalis cells isolated from an experimental endodontic infection. DNA sequences from 16 of these in vivo-induced (IVI) genes were determined. Results: Identified protein antigens of E. faecalis included enzymes involved in housekeeping functions, copper resistance protein, putative outer membrane proteins, and proteins of unknown function. Conclusions: In vivo expressed antigens of E. faecalis could be identified by using a novel immune-screening technique CMAT and an experimental animal model of endodontic infection. Detailed analysis of these IVI genes will lead to a better understanding of the molecular mechanisms involved in the endodontic infection of E. faecalis.

• Journal of Microbiology and Biotechnology
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• v.31 no.8
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• pp.1060-1068
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• 2021

Community-associated Methicillin-Resistant Staphylococcus aureus (CA-MRSA) is notorious as a leading cause of soft tissue infections. Despite several studies on the Agr regulator, the mechanisms of action of Agr on the virulence factors in different strains are still unknown. To reveal the role of Agr in different CA-MRSA, we investigated the LACΔagr mutant and the MW2Δagr mutant by comparing LAC (USA300), MW2 (USA400), and Δagr mutants. The changes of Δagr mutants in sensitivity to oxacillin and several virulence factors such as biofilm formation, pigmentation, motility, and membrane properties were monitored. LACΔagr and MW2Δagr mutants showed different oxacillin sensitivity and biofilm formation compared to the LAC and MW2 strains. Regardless of the strain, the motility was reduced in Δagr mutants. And there was an increase in the long chain fatty acid in phospholipid fatty acid composition of Δagr mutants. Other properties such as biofilm formation, pigmentation, motility, and membrane properties were different in both Δagr mutants. The Agr regulator may have a common role like the control of motility and straindependent roles such as antibiotic resistance, biofilm formation, change of membrane, and pigment production. It does not seem easy to control all MRSA by targeting the Agr regulator only as it showed strain-dependent behaviors.