• Mycobiology
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• 제46권4호
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• pp.370-381
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• 2018

Bioactive natural compounds, isolated from fungal endophytes, play a promising role in the search for novel drugs. They are an inspiring source for researchers due to their enormous structural diversity and complexity. During the present study fungal endophytes were isolated from a well-known medicinal shrub, Berberis aristata DC. and were explored for their antagonistic and antioxidant potential. B. aristata, an important medicinal shrub with remarkable pharmacological properties, is native to Northern Himalayan region. A total of 131 endophytic fungal isolates belonging to eighteen species and nine genera were obtained from three hundred and thirty surface sterilized segments of different tissues of B. aristata. The isolated fungi were classified on the basis of morphological and molecular analysis. Diversity and species richness was found to be higher in leaf tissues as compared to root and stem. Antibacterial activity demonstrated that the crude ethyl acetate extract of 80% isolates exhibited significant results against one or more bacterial pathogens. Ethyl acetate extract of Alternaria macrospora was found to have potential antibacterial activity. Significant antioxidant activity was also found in crude ethyl acetate extracts of Alternaria alternata and Aspergillus flavus. Similarly, antagonistic activity of the fungal endophytes revealed that all antagonists possessed inhibition potential against more than one fungal pathogen. This study is an important step towards tapping endophytic fungal diversity for bioactive metabolites which could be a step forward towards development of novel therapeutic agents.

• Journal of Forest and Environmental Science
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• 제34권5호
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• pp.376-381
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• 2018

For the control of oak wilt caused by Raffaelea quercus-mongolicae, an antifungal microorganism, Streptomyces blastmyceticus, was used as a potential agent. Culture suspension of S. blastmyceticus was injected into Quercus mongolicae in the research forest of Kangwon National University by $ChemJet^{(R)}$ trunk injection and Macro-infusion at root flare injection. $Alamo^{(R)}$ (a.i., propiconazole 14.5%), a fungicide currently used for the control of oak wilt in USA, was also treated by both methods to compare the efficacy. For preventive efficacy, culture suspension of the pathogen was inoculated at 1 month after injection of either agent. Tested trees were cut at 3 months after treatment, stained with 1% Fuchsin acid, and then non-conductive area (NCA) and re-isolation frequency (RIF) of oak wilt fungus were compared among treatments. While NCA was the highest as 47.3% in pathogen only treatment, it was the lowest as 16.0% in sterilized water treatment by Macro-infusion. NCAs of Alamo treatment by Macro-infusion and ChemJet injection were 25.3% and 32.1%, respectively. NCA of S.blastmyceticus treatment by ChemJet injection was 32.3%, similar with Alamo treatment's by ChemJet injection. All treatments by either injection method showed significantly lower NCA compared to the pathogen only treatment. These results indicate that S. blastmyceticus injection shows the preventive efficacy against oak wilt disease by suppressing the growth of pathogen injected. NCA of Macro-infusion injection of sterilized water was lower as 16.0%, compared to 21.3% of ChemJet injection. It means that Macro-infusion is more effective in translocation of sterilized water than ChemJet injection by even distribution. RIF from wood discs of treated trees showed high in pathogen only treatment, but relatively low in S. blastmyceticus treatment. RIF results were correlated with NCA results. From the above results, it was confirmed that S. blastmyceticus showed preventive efficacy against oak wilt disease by ChemJet trunk or Macro-infusion at root flare injection.

• 한국균학회지
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• 제40권2호
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• pp.118-123
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• 2012

대표적인 감귤 녹색곰팡이병(Penicillium digitatum) 방제용 생물농약을 개발하고자 제주도내 7개 과수원으로부터 채집된 citrus 잎에서 21균주의 내생세균을 분리하였다. 그 중 5개의 세균이 녹색곰팡이병균 P. digitatum에 항균활성을 나타냈으며, 대치배양에서 가장 강력한 항균활성을 보인 CB3 균주가 선발되었다. CB3 균주는 간상형의 그람 양성세균으로 생리 생화학적 특성과 gyrA 유전자 염기서열 분석에 의해 Bacillus velezensis로 동정되었다. CB3 균주는 감귤 저장병 병원균 Penicillium digitatum에 강력한 항균활성을 나타내었다. $1{\times}10^5$ spores/ml에 이르는 고농도의 P. digitatum을 감귤에 상처접종했을 때에도, $1{\times}10^8$ cfu/ml의 CB3에 의한 방제효과는 66.7%로 매우 높았다. 본 연구결과, Bacillus velezensis CB3의 안정성과 강한 방제활성 등을 고려할 때 유용 친환경적 방제제로서 매우 가치가 있을 것으로 판단된다.

• 한국어병학회지
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• 제30권2호
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• pp.135-148
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• 2017

Pathogen introductions associated with aquatic invasive species threaten ecosystems and biodiversity worldwide. Bigheaded carps (BHC), including Silver Carp Hypophthalmichthys molitrix, Bighead Carp H. nobilis, and their hybrids, are prolific, invasive pests in central US rivers. However, little is known about pathogen effects on invading BHC or how BHC affect the disease risk profile for native fishes in receiving ecosystems. We therefore conducted, from May 2013-December 2014, a systematic pathogen survey for BHC and native fishes in the Wabash River watershed, Indiana, USA. We found Pseudomonas fluorescens, P. putida, and Salmonella enterica DNA in BHC as well as native fishes, although none of these bacteria were exclusively present in BHC. DNA from other bacterial taxa was detected only in native fishes and Common Carp Cyprinus carpio. No gastrointestinal helminths were detected in BHC, although they were common in most native fishes examined. We also conducted in vitro studies on BHC tissues (skin, gill, fin, and fry) and found high sensitivity to Largemouth Bass virus, viral hemorrhagic septicemia virus, and infectious pancreatic necrosis virus. We conclude that BHC are not heavily burdened by bacteria, viruses and parasites in the invaded study ecosystems, although they do harbor native bacteria and show potential for high sensitivity to endemic viruses.

• The Plant Pathology Journal
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• 제32권4호
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• pp.347-356
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• 2016

Plants protect themselves from pathogen attacks via several mechanisms, including hypersensitive cell death. Recognition of pathogen attack by the plant resistance gene triggers expression of carboxylesterase genes associated with hypersensitive response. We identified six transcripts of carboxylesterase genes, Vitis flexuosa carboxylesterase 5585 (VfCXE5585), Vf-CXE12827, VfCXE13132, VfCXE17159, VfCXE18231, and VfCXE47674, which showed different expression patterns upon transcriptome analysis of V. flexuosa inoculated with Elsinoe ampelina. The lengths of genes ranged from 1,098 to 1,629 bp, and their encoded proteins consisted of 309 to 335 amino acids. The predicted amino acid sequences showed hydrolase like domains in all six transcripts and contained two conserved motifs, GXSXG of serine hydrolase characteristics and HGGGF related to the carboxylesterase family. The deduced amino acid sequence also contained a potential catalytic triad consisted of serine, aspartic acid and histidine. Of the six transcripts, Vf-CXE12827 showed upregulated expression against E. ampelina at all time points. Three genes (VfCXE5585, VfCXE12827, and VfCXE13132) showed upregulation, while others (VfCXE17159, VfCXE18231, and VfCXE47674) were down regulated in grapevines infected with Botrytis cinerea. All transcripts showed upregulated expression against Rhizobium vitis at early and later time points except VfCXE12827, and were downregulated for up to 48 hours post inoculation (hpi) after upregulation at 1 hpi in response to R. vitis infection. All tested genes showed high and differential expression in response to pathogens, indicating that they all may play a role in defense pathways during pathogen infection in grapevines.

• The Plant Pathology Journal
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• 제29권1호
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• pp.42-51
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• 2013

One of the most important limiting factors for the production of the grafted cactus in Korea is the qualitative and quantitative yield loss derived from stem rots especially caused by Bipolaris cactivora. This study is aimed to develop microbial control agents useful for the control of the bipolaris stem rot. Two bacteria (GA1-23 and GA4-4) selected out of 943 microbial isolates because of their strong antibiotic activity against B. cactivora were identified as Bacillus subtilis and B. amyloliquefaciens, respectively, by the cultural characteristics, Biolog program and 16S rRNA sequencing analyses. Both bacterial isolates significantly inhibited the conidial germination and mycelial growth of the pathogen with no significant difference between the two, of which the inhibitory efficacies varied depending on the cultural conditions such as temperature, nutritional compositions and concentrations. Light and electron microscopy of the pathogen treated with the bacterial isolates showed the inhibition of spore germination with initial malformation of germ tubes and later formation of circle-like vesicles with no hyphal growth and hyphal disruption sometimes accompanied by hyphal swellings and shrinkages adjacent to the bacteria, suggesting their antibiotic mode of antagonistic activity. Control efficacy of B. subtilis GA1-23 and B. amyloliquefaciens GA4-4 on the cactus stem rot were not as high as but comparable to that of fungicide difenoconazole when they were treated simultaneously at the time of pathogen inoculation. All of these results suggest the two bacterial isolates have a good potential to be developed as biocontrol agents for the bipolaris stem rot of the grafted cactus.

• Journal of Microbiology and Biotechnology
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• 제30권9호
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• pp.1335-1342
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• 2020

The identification of bacterial pathogens to humans is critical for environmental microbial risk assessment. However, current methods for identifying pathogens in environmental samples are limited in their ability to detect highly diverse bacterial communities and accurately differentiate pathogens from commensal bacteria. In the present study, we suggest an improved approach using a combination of identification results obtained from multiple databases, including the multilocus sequence typing (MLST) database, virulence factor database (VFDB), and pathosystems resource integration center (PATRIC) databases to resolve current challenges. By integrating the identification results from multiple databases, potential bacterial pathogens in metagenomes were identified and classified into eight different groups. Based on the distribution of genes in each group, we proposed an equation to calculate the metagenomic pathogen identification index (MPII) of each metagenome based on the weighted abundance of identified sequences in each database. We found that the accuracy of pathogen identification was improved by using combinations of multiple databases compared to that of individual databases. When the approach was applied to environmental metagenomes, metagenomes associated with activated sludge were estimated with higher MPII than other environments (i.e., drinking water, ocean water, ocean sediment, and freshwater sediment). The calculated MPII values were statistically distinguishable among different environments (p < 0.05). These results demonstrate that the suggested approach allows more for more accurate identification of the pathogens associated with metagenomes.

• The Plant Pathology Journal
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• 제36권6호
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• pp.600-607
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• 2020

Phytophthora capsici Leonian is a major pathogen of pepper worldwide and few resistance sources to this pathogen have been identified so far. The goals of this study were to identify new sources of resistance against P. capsici in Capsicum landraces and analyze the relationship between the resistance indicator of plant symptoms and some plant phenotype parameters of plant height, stem width, leaf length and leaf width. Thirty-two landraces of pepper were collected from fourteen states in Mexico. From each population, 36 plants were inoculated with 10,000 zoospores of P. capsici under controlled conditions. This experiment was repeated twice. Out of the 32 landraces, six showed high level of resistance, four showed intermediate resistance and five showed low level of resistance when compared with the susceptible control 'Bravo' and the resistant control 'CM334', indicating that these landraces are promising novel sources of resistance to P. capsici. There was no correlation between the symptoms and plant phenotype parameters. However, these parameters were not affected in the group classified as highly resistant, indicating that P. capsici does not affect the growing of these resistant pepper landraces. The other resistant groups were significantly affected in a differently manner regarding their phenotype, indicating that this pathogen reduce their growth in different ways. This study reports novel resistance sources with great potential that could be used in breeding programs to develop new pepper cultivars with durable resistance to P. capsici.

• BMB Reports
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• 제38권1호
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• pp.82-88
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• 2005

Bacillus cereus 28-9 is a chitinolytic bacterium isolated from lily plant in Taiwan. This bacterium exhibited biocontrol potential on Botrytis leaf blight of lily as demonstrated by a detached leaf assay and dual culture assay. At least two chitinases (ChiCW and ChiCH) were excreted by B. cereus 28-9. The ChiCW-encoding gene was cloned and moderately expressed in Escherichia coli DH5$\alpha$. Near homogenous ChiCW was obtained from the periplasmic fraction of E. coli cells harboring chiCW by a purification procedure. An in vitro assay showed that the purified ChiCW had inhibitory activity on conidial germination of Botrytis elliptica, a major fungal pathogen of lily leaf blight.

• 한국식품위생안전성학회:학술대회논문집
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• 한국식품위생안전성학회 1999년도 추계학술세미나 및 학술발표회 - 식품의 위생관리와 안전성평가에 대한 최근 연구동향
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• pp.29-70
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• 1999

Current food sanitation systems for meat and livestock in Australia ar underpinned by HACCP-based quality assurance. HACCP-based quality assurance programs have been implemented by all australian red meat industry sectors, from 'farm-to-fork'. These quality assurance programs are (along with other quality and food safety considerations) the collection of a series of sanitation steps and strategies that aim to ensure that only healthy, clean livestock are presented for slaughter; those healthy, clean animals enter a clean processing plant; contact of carcase surfaces with potential sources of contamination is avoided; carcase surfaces are decontaminated before chilling; and subsequent growth of potential contaminants is avoided. Prospects for food sanitation systems for meat and livestock in Australia lie largely in enhancing current and applying new sanitation strategies and procedures within our HACCP-based quality assurance framework. Prospects include increased focus on actual (Versus perceived) risks; on-farm/feedlot pathogen elimination; increased implementation of existing (or new) decontamination technologies; and an improved cold chain.