• Genomics & Informatics
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• 제21권4호
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• pp.52.1-52.10
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• 2023

Accurate and efficient microbial diagnosis is crucial for effective molecular diagnostics, especially in the field of human healthcare. The gold standard equipment widely employed for detecting specific microorganisms in molecular diagnosis is quantitative real-time polymerase chain reaction (qRT-PCR). However, its limitations in low metagenomic DNA yield samples necessitate exploring alternative approaches. Digital PCR, by quantifying the number of copies of the target sequence, provides absolute quantification results for the bacterial strain. In this study, we compared the diagnostic efficiency of qRT-PCR and digital PCR in detecting a particular bacterial strain (Staphylococcus aureus), focusing on skin-derived DNA samples. Experimentally, specific primer for S. aureus were designed at transcription elongation factor (greA) gene and the target amplicon were cloned and sequenced to validate efficiency of specificity to the greA gene of S. aureus. To quantify the absolute amount of microorganisms present on the skin, the variable region 5 (V5) of the 16S rRNA gene was used, and primers for S. aureus identification were used to relative their amount in the subject's skin. The findings demonstrate the absolute convenience and efficiency of digital PCR in microbial diagnostics. We suggest that the high sensitivity and precise quantification provided by digital PCR could be a promising tool for detecting specific microorganisms, especially in skin-derived DNA samples with low metagenomic DNA yields, and that further research and implementation is needed to improve medical practice and diagnosis.

• The Plant Pathology Journal
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• 제27권4호
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• pp.301-309
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• 2011

The filamentous fungus Fusarium graminearum is an important cereal pathogen. Although quantitative realtime PCR (qRT-PCR) is commonly used to analyze the expression of important fungal genes, no detailed validation of reference genes for the normalization of qRT-PCR data has been performed in this fungus. Here, we evaluated 15 candidate genes as references, including those previously described as housekeeping genes and those selected from the whole transcriptome sequencing data. By a combination of three statistical algorithms (BestKeeper, geNorm, and NormFinder), the variation in the expression of these genes was assessed under different culture conditions that favored mycelial growth, sexual development, and trichothecene mycotoxin production. When favoring mycelial growth, GzFLO and GzUBH expression were most stable in complete medium. Both EF1A and GzRPS16 expression were relatively stable under all conditions on carrot agar, including mycelial growth and the subsequent perithecial induction stage. These two genes were also most stable during trichothecene production. For the combined data set, GzUBH and EF1A were selected as the most stable. Thus, these genes are suitable reference genes for accurate normalization of qRT-PCR data for gene expression analyses of F. graminearum and other related fungi.

• 식물병연구
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• 제27권3호
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• pp.120-127
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• 2021

식물 바이러스는 작물 수확량에 상당한 손실을 일으키고 작물 생산을 지속적으로 위협하여 세계 식량 안보에 심각한 위협이 된다. 그 중 tomato spotted wilt virus (TSWV)는 주로 원예작물을 감염시키는 가장 위협적인 식물 바이러스로 넓은 기주 범위를 가진다. Reverse-transcription quantitative real-time PCR (RT-qPCR)은 TSWV의 민감한 검출을 위해 널리 사용되고 있지만 표준화의 어려움으로 인해 유용성이 감소한다. 따라서 본 연구에서는 TSWV 검출을 위해 민감하고 정확한 reverse transcription droplet digital polymerase chain reaction (RT-ddPCR)을 확립하였다. TSWV 검출에 대한 RT-qPCR 및 RT-ddPCR의 민감도를 비교하였고, TSWV에 대한 RT-ddPCR의 특이성 분석은 고추에서 주로 발생하는 바이러스 및 음성 대조군에서 특이성을 확인한 결과 증폭되지 않았다. RT-ddPCR 및 RTqPCR에 의해 측정된 TSWV의 선형회귀곡선은 모두 높은 선형성을 나타냈지만, RT-ddPCR 분석이 10배 이상 더 민감하고 더 낮은 TSWV의 copy 수를 검출할 수 있었다. 종합적으로, 우리의 연구 결과는 RT-ddPCR이 TSWV 검출에 대해 높은 민감도와 특이성을 제공하고 낮은 농도의 현장 시료에서 TSWV 검출하는 데 적합하다는 것을 보여준다.

• The Plant Pathology Journal
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• 제39권4호
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• pp.309-318
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• 2023

Huanglongbing (HLB) is one of the most destructive diseases in citrus, which imperils the sustainability of citriculture worldwide. The presumed causal agent of HLB, 'Candidatus Liberibacter asiaticus' (CLas) is a non-culturable phloem-limited α-proteobacterium transmitted by Asian citrus psyllids (ACP, Diaphorina citri Kuwayama). A widely adopted method for HLB diagnosis is based on quantitative real-time polymerase chain reaction (qPCR). Although HLB diagnostic qPCR provides high sensitivity and good reproducibility, it is limited by time-consuming DNA preparation from plant tissue or ACP and the requirement of proper lab instruments including a thermal cycler to conduct qPCR. In an attempt to develop a quick assay that can be deployed in the field for CLas detection, we developed a real-time loop-mediated isothermal amplification (rt-LAMP) assay by targeting the CLas five copy nrdB gene. The rt-LAMP assay using various plant sample types and psyllids successfully detected the nrdB target as low as ~2.6 Log10 copies. Although the rt-LAMP assay was less sensitive than laboratory-based qPCR (detection limit ~10 copies), the data obtained with citrus leaf and bark and ACP showed that the rt-LAMP assay has >96% CLas detection rate, compared to that of laboratory-based qPCR. However, the CLas detection rate in fibrous roots was significantly decreased compared to qPCR due to low CLas titer in some root DNA sample. We also demonstrated that the rt-LAMP assay can be used with a crude leaf DNA extract which is fully deployable in the field for quick and reliable HLB screening.

• 한국식품저장유통학회지
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• 제30권3호
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• pp.383-394
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• 2023

The ultra-fast quantitative real-time polymerase chain reaction (qPCR) assay was developed and validated to differentiate the morphologically similar ones, Oncorhynchus keta and Oncorhynchus mykiss. Species-specific primers were designed for the COI genes of mtDNA. The species-specific primers designed for O. keta and O. mykiss were selectively amplified by O. keta and O. mykiss DNA, respectively. The sensitivity of O. keta and O. mykiss primers was 1 ng/μL. Quantitative testing showed that the results met the 'Guidelines on Standard Procedures for Preparing Analysis Method such as Food' proposed by the Ministry of Food and Drug Safety. The qPCR method developed and validated in this study for identifying O. keta and O. mykiss has advantages such as speed and field applicability. Therefore, this method is expected to help control forgery and alteration of raw materials in the seafood industry.

• 미생물학회지
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• 제47권1호
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• pp.30-37
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• 2011

조류 인플루엔자 바이러스(AIV) 아형을 ultra-time PCR법(UPCR)을 이용하여 초스피드로 진단할 수 있는 방법을 고안하였다. 표적 대상의 프라이머는 AIV H5N1 아형의 hemagglutinin(HA) 유전자 중 가장 상보성이 높은 133 bp의 부위를 선택하였고, 실험의 안전을 위하여 인공합성의 방법으로 제작하였다. 압타머와 결합한 molecular beacon 기반 Mini-Opticon Q-PCR 기기를 사용한 UPCR법으로, 총 UPCR 반응액의 양을 10 ${\mu}l$으로, UPCR과 용융온도 분석시간을 15분 이내로 매우 짧게 단축시켰다. 민감도 측정에서 최소의 주형인 5분자의 HA 유전자만으로 정확히 AIV의 특이적 133 bp를 합성하였다. UPCR로 디자인된 이 PCR은 AIV 아형의 진단에 적용될 수 있을 뿐 아니라, UPCR이 기반되는 진단을 이용하여 다른 병원체에도 널리 적용 될 수 있을 것으로 기대된다.

• 한국물환경학회지
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• 제34권1호
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• pp.46-56
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• 2018

A mcyB-specific Ultra-Rapid quantitative PCR was developed for the quantitative detection of Microcystis aeruginosa, which is often a dominant species in green tide. McyB-specific UR-qPCR was optimized under extremely short times of each step in thermal cycles, based on the specific primers deduced from the mcyB in microcystin synthetase of M. aeruginosa. The M. aeruginosa strain KG07 was used as a standard for quantification, after the microscopic counting and calculation by mcyB-specific UR-qPCR. The water samples from the river water with the Microcystis outbreak were also measured by using both methods. The $1.0{\times}10^8$ molecules of mcyB-specific DNA was recognized inner 4 minutes after beginning of UR-qPCR, while $1.0{\times}10^4$ molecules of mcyB-specific templates was detected inner 7 minutes with quantitative manner. From the range of $1.0{\times}10^2$ to $1.0{\times}10^8$ initial molecules, quantification was well established based on $C_T$ using mcyB-specific UR-qPCR (Regression coefficiency, $R^2=0.9977$). Between the numbers of M. aeruginosa cell counting under microscope and calculated numbers using mcyB-specific UR-qPCR, some differences were often found. The reasons for these differences were discussed; therefore, easy compensation method was proposed that was dependent on the numbers of the cell counting. Additionally, to easily extract the genomic DNA (gDNA) from the samples, a freeze-fracturing of water-sample using liquid nitrogen was tested, by excluding the conventional gDNA extraction method. It was also verified that there were no significant differences using the UR-qPCR with both gDNAs. In conclusion, the mcyB-specific UR-qPCR that we proposed would be expected to be a useful tool for rapid quantification and easy monitoring of M. aeruginosa in environmental water.

• 한국산학기술학회논문지
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• 제20권12호
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• pp.117-124
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• 2019

비브리오 콜레라는 수산물과 선박평형수 내에서 모니터링되고 있는 중요 병원성 박테리아이다. 이를 검출하기 위한 여러 방법들이 개발되어 왔으나, 시간 소모가 크고 민감도에서 한계가 있었다. 본 연구는 비브리오 콜레라를 보다 정확하게 검출하기 위한 방법을 개발하는 목적으로 수행하였다. PNA 기반 비대칭 real-time PCR 기술에 적용하기 위하여 펩티드 핵산(Peptide nucleic acid, PNA) 프로브를 개발하였다. 독성 유전자인 Cholera enterotoxin subunit B (ctxB)를 비브리오 콜레라 검출을 위한 타겟 유전자로 선정하고, conventional PCR과 real-time PCR을 위한 positive template를 합성하였다. Real-time PCR 프라이머와 PNA 프로브를 디자인하여, 정량 분석을 위한 표준곡선 실험을 수행하였다. 선택된 PNA 프로브는 비브리오 콜레라에 특이적으로 반응하였으며, 검출한계는 0.1 cfu/100 mL이었다. 종합해 보면, 본 연구에서 개발된 PNA 프로브와 비대칭 real-time PCR 방법은 수산물과 선박평형수 뿐만 아니라 해양환경에 있는 비브리오 콜레라를 신속하고 정확하게 모니터링할 수 있는 기술로 판단된다.

• 한국식품위생안전성학회지
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• 제33권1호
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• pp.71-76
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• 2018

노로바이러스는 전 세계적으로 산발적인 발병 관련 비세균성 위장염의 주요 원인 물질이다. 노로바이러스 검출을 위해 역전사 실시간 PCR (RT qPCR)이 그 민감도와 특이성으로 인해 주요 수단으로 빠르게 자리 잡았다. 그러나 RT qPCR 분석을 위해서는 정확한 바이러스 RNA 추출방법이 필수적이다. TRIzol 시약은 생물학적 물질로부터 RNA의 추출에 이용되고 따라서 노로바이러스 RNA 추출에도 널리 사용된다. 이 연구에서는 인체 노로바이러스 유전체 그룹 I (GI) 및 유전자 그룹 II (GII)와 생쥐 노로바이러스(GV) 중에서 GII로부터의 TRIzol 을 이용한 바이러스 RNA의 추출률이 바이러스 시료 용액의 pH에 의존했다는 내용이 다루어졌다. 실시간 PCR의 Ct값으로 비교한 RNA 추출 수율은 산성 영역보다 알칼리성 pH에서 높았다. 이 연구 결과로 부터 TRIzol을 이용하여 GII RNA를 추출하여 노로바이러스를 정량적으로 분석할 때 pH조건이 대단히 중요하다는 것을 알 수 있었다.

• Genomics & Informatics
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• 제21권1호
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• pp.13.1-13.8
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• 2023

Importance of accurate molecular diagnosis and quantification of particular disease-related pathogenic microorganisms is highlighted as an introductory step to prevent and care for diseases. In this study, we designed a primer/probe set for quantitative real-time polymerase chain reaction (qRT-PCR) targeting rgpA gene, known as the specific virulence factor of periodontitis-related pathogenic bacteria 'Porphyromonas gingivalis', and evaluated its diagnostic efficiency by detecting and quantifying relative bacterial load of P. gingivalis within saliva samples collected from clinical subjects. As a result of qRT-PCR, we confirmed that relative bacterial load of P. gingivalis was detected and quantified within all samples of positive control and periodontitis groups. On the contrary, negative results were confirmed in both negative control and healthy groups. Additionally, as a result of comparison with next-generation sequencing (NGS)-based 16S metagenome profiling data, we confirmed relative bacterial load of P. gingivalis, which was not identified on bacterial classification table created through 16S microbiome analysis, in qRT-PCR results. It showed that an approach to quantifying specific microorganisms by applying qRT-PCR method could solve microbial misclassification issues at species level of an NGS-based 16S microbiome study. In this respect, we suggest that P. gingivalis-specific primer/probe set introduced in present study has efficient applicability in various oral healthcare industries, including periodontitis-related microbial molecular diagnosis field.