• 미생물학회지
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• 제34권4호
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• pp.248-253
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• 1998

Esherichia coli(E. coli) K12 균주를 숙주세포로 삼는 박테리오파아지인 N4는 single-stranded DNA에 결합하는 단백질인 N4SSB(bacteriophage N4-coded single-stranded DNA-binding protein) 단백질을 만든다. N4SSB 단백질은 N4 DNA replication 뿐만 아니라 late transcription과 N4 DNA recombination에도 필요한 여러 가지 기능을 가진 단백질이다. N4 late transcription은 숙주세포인 E. coli의 $E{\sigma}^{70}$ RNA polymerase에 의해서 수행이 되나 N4SSB 단백질을 반드시 필요로 하기 때문에 N4SSB 단백질이 생성될 때까지는 N4 late promoter로부터 RNA 합성이 일어나지 않는다. 본 연구에서는 N4SSB의 N4 DNA replication과 late transcription, 그리고 N4 DNA recombination에 필요한 영역(domain)을 알아내기 위해서 여러 가지 돌연변이형 N4SSB 단백질을 만들어 N4 DNA replication과 late transcription, 그리고 N4 DNA recombination의 3가지 작용에 대한 in vivo 활성을 조사 분석하였다. 그 결과 N4SSB 단백질의 C-말단기에 있는 7개의 아미노산이 N4SSB 단백질의 활성에 중요하다는 것을 알 수 있었다. 특히 C-말단기의 7개의 아미노산에는 세 개의 lysine이 포함되어 있는데 이 lysine이 N4SSB 단백질의 활성에 중요한 역할을 한다는 것이 제시되었다.

• The Plant Pathology Journal
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• 제17권1호
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• pp.62-66
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• 2001

Detection of Xanthomonas axonopodis pv. citri (Xac) on citrus fruits for exporting is usually made by bacteriophage test (BPT) to demonstrate the pathogen-free status. BPT has rather time-consuming and complicate procedures for dealing with massive samples to be inspected. In this study, enzyme-linked immunosorbent assay (ELISA) was applied to detect Xac on fruits, and compared with BPT. In ELISA, positive reactions occurred in the bacterial densities of $3\times10^5$ cells/ml or more. To detect the bacterial infection on citrus fruits with a density of lower than $3\times10^5$ cells/ml, the bacterial suspensions were mixed with fruit rinse water and incubated in broth medium. Ordinary peptone sucrose broth (PSB) was not a proper medium for increasing Xac density specifically enough to be detect by ELISA. On the other hand, modified PSB (MPSP) amended with Fe-EDTA (0.25 g/$\ell$) and 2.5% potato-dextrose broth sufficed to differentiate uninfected and infected citrus fruits by ELISA after 24 h incubation of the fruit rinse water. Using various citrus samples from infected and uninfected fields, efficiencies in detecting Xac on fruits were compared between ELISA and BPT. For infected fruits samples, ELISA detected Xac by 100%, while BPT by about 44%, indicating that the detection efficiency was improved by 23.5% by ELISA, compared to BPT. In addition, ELISA has simpler procedures for testing and is less time-consuming than BPT, suggesting that ELISA may be accurate and simple method to detect Xac on citrus fruits.

• The Plant Pathology Journal
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• 제40권2호
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• pp.160-170
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• 2024

Erwinia amylovora is a plant pathogen that causes fire blight on apples and pears. Bacteriophages, which are viruses that selectively infect specific species of bacteria and are harmless to animal cells, have been considered as biological control agents for the prevention of bacterial pathogens. In this study, we aimed to use bacteriophages that infect E. amylovora as biocontrol agents against fire blight. We isolated bacteriophages Fifi044 and Fifi318 infecting E. amylovora, and characterized their morphology, plaque form, and genetic diversity to use as cocktails for disease control. The stabilities of the two phages were investigated at various temperatures and pH values and under sunlight, and long-term storage experiment was conducted for a year. To evaluate whether the two phages were suitable for use in cocktail form, growth curves of E. amylovora were prepared after treating the bacterial cells with single phages and a phage cocktail. In addition, a disease control test was conducted using immature apples and in vitro cultured apple plantlets to determine the biocontrol effects of the phage cocktail. The two phages were morphologically and genetically different, and highly stable up to 50℃ and pH value from 4 to 10. The phages showed synergistic effect when used as a cocktail in the inhibition of host bacterial growth and the disease control. This study demonstrated that the potential of the phage cocktail as a biocontrol agent for commercial use.

• Journal of Microbiology and Biotechnology
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• 제28권12호
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• pp.2064-2070
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• 2018

Pseudomonas tolaasii 6264 is a representative strain that causes bacterial blotch disease on the cultivated oyster mushroom, Pleurotus ostreatus. Bacteriophages are able to sterilize the pathogenic P. tolaasii strains, and therefore, they can be applied in creating disease-free mushroom cultivation farms, through a method known as "phage therapy". For successful phage therapy, the characterization of phage-resistant strains is necessary, since they are frequently induced from the original pathogenic bacteria in the presence of phages. When 10 different phages were incubated with P. tolaasii 6264, their corresponding phage-resistant strains were obtained. In this study, changes in pathogenic, genetic, and biochemical characteristics as well as the acquired phage resistance of these strains were investigated. In the phylogenetic analyses, all phage-resistant strains were identical to the original parent strain based on the sequence comparison of 16S rRNA genes. When various phage-resistant strains were examined by three different methods, pitting test, white line test, and hemolytic activity, they were divided into three groups: strains showing all positive results in three tests, two positive in the first two tests, and all negative. Nevertheless, all phage-resistant strains showed that their pathogenic activities were reduced or completely lost.

• 한국입자에어로졸학회지
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• 제15권4호
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• pp.173-182
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• 2019

Since airborne viruses have been known to aggravate indoor air quality, studies on the development of anti-viral air filter increase recently. In this study, the pressure drop and anti-viral efficiency of TiO₂ coated ceramic ball filter were evaluated. After the filter being inserted into a commercial room air cleaner, chamber test with aerosolized bacteriophage MS2 was performed. The porosity of TiO₂ coated ceramic ball filter was 0.85, and pressure drop was about 13 Pa for 1 m/s of air velocity. The anti-viral efficiency was about 93% when the reaction time was 25 minutes in a 1 ㎥ chamber.

• 대한수의학회지
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• 제40권1호
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• pp.49-55
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• 2000

Lysogenic conversion of Staphylococcus aureus to loss of ${\beta}-hemolysin$ production by serological group F phages is always associated with gain in staphylokinase production. In this study, the new phages belonging to serotype F were detected during the course of isolation of phages from Staph aureus of bovine origin and some characteristics of the new phages isolated were investigated. The new phages, ${\phi}470$ and ${\phi}499$, isolated from Staph aureus producing ${\beta}-hemolysin$ and staphylokinase(${\beta}^+\;K^+$) were found to convert ${\beta}^+\;K^+$ strain to ${\beta}^+K\;^+$, Staph aureus strains lysogenized by this serotype F single-converting phage ${\phi}470$ or ${\phi}499$ could be again lysogenized with serotype F double-converting phage ${\phi}506$. The frequency of lysogenization of indicator strains by serotype F single-converting phage was 100%, whereas the frequency for serotype F double-converting phage ${\phi}506$ varied from 4.2% to 97.6% according to the indicator strains. The indicator strain lysogenized with phage ${\phi}470$ was resistant to phage ${\phi}499$, and vice versa, but not to phage ${\phi}506$. Therefore, phage ${\phi}470$ and ${\phi}499$ were shown to be identical by immunity test.

• 한국축산식품학회지
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• 제38권1호
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• pp.88-98
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• 2018

In this study, we isolated and characterized a bacteriocin-producing strain and two bacteriophages (P4, A3), showing antimicrobial effects against Clostridium perfringens, from chicken and swine feces by the spot-on-the lawn antagonism method. The selected strain was identified as Streptococcus hyointestinalis by 16S rRNA gene sequencing. The bacteriocin from the isolated strain exhibited strong inhibitory activity against four strains of C. perfringens and all the tested strains of Listeria monocytogenes, and the bacteriocin were highly heat- and pH-stable even at pH 2, pH 10 and $121^{\circ}C$ for 15 min. We also evaluated the combined effects of the isolated bacteriocin and phages. Combining the phage treatments and bacteriocin resulted in a synergetic effect compared with the phage or the bacteriocin alone. In addition, during the probiotic test, the bacteriocin-producing S. hyointestinalis B19 strain reduced the population of C. perfringens significantly. Treatment with S. hyointestinalis B19 and a cocktail of lytic bacteriophages eradicated the C. perfringens KCTC $3269^T$, completely. Consequently, the isolated bacteriocin and bacteriophages represent candidates for effective biocontrol of C. perfringens, and bacteriocin-producing S. hyointestinalis B19 is a potential probiotic candidate for use in domestic animals.

• 한국식품과학회지
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• 제52권1호
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• pp.109-112
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• 2020

본 연구에서는 6종의 E. coli 및 S. aureus 유래 박테리오파지 용액에 존재하는 내독소 함량 조사와 파지의 세포독성 여부에 대해 평가하였다. 대표적인 생물학적 내독소 시험법인 LAL assay을 시행하여 9-10 log PFU/mL 농도의 내독소 함량을 확인한 결과, 파지의 임상적용에는 부적합한 수치이나 식품에 존재하는 병원균의 살균 목적의 사용에는 매우 유해하지 않은 수치임을 확인할 수 있었다. 박테리오파지 용액의 세포독성평가를 확인하기 위해 MTT 분석을 시행하여 세포 생존율을 확인하였다. E. coli 파지 용액과 S. aureus 파지 용액 처리군 모두에서 98% 이상의 생존율이 관찰되어 파지용액에 존재하는 내독소 및 파지가 세포독성을 유발하지 않는다는 것을 확인하였다. 그러므로 일반적인 방법으로 증폭, 농축한 파지 용액은 인체에 대한 유해성이 적으며 식품에 살균소독제로 적용하더라도 문제가 없을 것으로 사료된다.

• The Plant Pathology Journal
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• 제37권6호
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• pp.555-565
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• 2021

Bacteriophages infecting Acidovorax citrulli, the causal agent of bacterial fruit blotch, have been proven to be effective for the prevention and control of this disease. However, the occurrence of bacteriophage-resistant bacteria is one of hurdles in phage biocontrol and the understanding of phage resistance in this bacterium is an essential step. In this study, we aim to investigate possible phage resistance of A. citrulli and relationship between phage resistance and pathogenicity, and to isolate and characterize the genes involved in these phenomena. A phage-resistant and less-virulent mutant named as AC-17-G1 was isolated among 3,264 A. citrulli Tn5 mutants through serial spot assays and plaque assays followed by pathogenicity test using seed coating method. The mutant has the integrated Tn5 in the middle of a cupin protein gene. This mutant recovered its pathogenicity and phage sensitivity by complementation with corresponding wild-type gene. Site-directed mutation of this gene from wild-type by CRISPR/Cas9 system resulted in the loss of pathogenicity and acquisition of phage resistance. The growth of AC-17-G1 in King's B medium was much less than the wild-type, but the growth turned into normal in the medium supplemented with D-mannose 6-phosphate or D-fructose 6-phosphate indicating the cupin protein functions as a phosphomannos isomerase. Sodium dodecyl sulfa analysis of lipopolysaccharide (LPS) extracted from the mutant was smaller than that from wild-type. All these data suggest that the cupin protein is a phosphomannos isomerase involved in LPS synthesis, and LPS is an important determinant of pathogenicity and phage susceptibility of A. citrulli.

• 한국어병학회지
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• 제24권2호
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• pp.85-93
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• 2011

Edwardsiella tarda (E. tarda)는 담수 및 해수어에 광범위하게 감염을 일으키는 그람 음성 박테리아이다. 본 연구에서는 서해안 넙치 양식장에서 분리한 E. tarda에 대해 특이 용균을 보이는 파아지를 분리하여 파아지의 활성에 미치는 환경적 요인인 pH와 배양 온도의 영향 등을 조사하였다. 또한 어류모델로서는 담수어종인 Nile tilapia (Oreochromis niloticus)를 이용하였으며 E. tarda와 파아지와의 상호작용을 알아보았다. pH 안정성 실험에서는 담수보다 해수에서 높은 활성을 보였으며 온도 안정성 실험 결과 $50^{\circ}C$까지 일정한 활성을 보였다. Tilapia 감염 실험에서는 파아지와 E. tarda를 접종하였다. 그 결과 실험군은 대조군에 비해 24시간째까지 E. tarda수가 일정하게 감소하는 것을 확인하였으며 파아지는 처음 접종 양보다 약간 증폭됨을 알 수 있었다. 본 연구의 결과는 E. tarda에 의해 발생되는 질병을 특이 파아지를 이용하여 제어할 수 있음을 암시해준다.