• Journal of Microbiology and Biotechnology
• /
• v.9 no.3
• /
• pp.352-357
• /
• 1999

Enterobacter sp. B54 inhibited growth of the fungus Phytophthora capsici on potato dextrose agar (PDA). Three mutants with antifungal activities (denoted M54-47, M54-113, and M54-329) which were lost or increased, through Pl::Tn5 lac mutagenesis, were used to isolate genes responsible for fungal inhibition on PDA. Two clones were selected from the partially EcoR1-digested genomic library of the wild-type strain by probing with genomic flanking sequences of each mutant. We have isolated a 20-kb EcoR1 genomic DNA fragment from this strain that contains genes involved in hyphal growth inhibition of P. capsici on PDA. Subcloning and expression analysis of the above DNA fragment identified a 8-kb region which was necessary for antifungal activities. A 8-kb HindⅢDNA fragment covers three genomic loci inserted by Tn5 lac in each mutant. This suggested that all genes which are related to antifungal activities might be clustered in simple forms of at least 5-8 kb sizes.

• Research in Plant Disease
• /
• v.24 no.3
• /
• pp.213-220
• /
• 2018

We classified the previously reported antagonistic strains of Sorangium cellulosum into 5 subspecies (A-E). Four strains were antagonistic to Botrytis cinerea (AB group) and two strains were antagonistic to Colletotrichum acutatum (AC group). According to the genetic and sequential analyses with standard genes, xynB1, bglA2, groEL1 for grouping, all strains of AB group were belonged to subspecies C and all strains of AC group were belonged to subspecies D. In addition, high pressure liquid chromatography with the culture filtrates confirmed the genetic results, because AB group had peaks with retention time at 20-22.5 minutes, whereas AC group had no peak. There was positive relationship ($R^2=0.9652$) between the control values of infecting B. cinerea on cherry tomatoes and the main peak areas of chromatograms among the four isolates of AB group. From the subspecies results of AB group, the main peak of KYC 3270 was expected to be epothilone D. However the retention times of the standard of commercial epothilone D and the main peak of KYC 3270 culture filtrate were different as 9.9 and 11.581 min., respectively. Finally, the antagonistic metabolite of AB group was inferred as 7-ketone epothilone D.

• Microbiology and Biotechnology Letters
• /
• v.20 no.6
• /
• pp.619-624
• /
• 1992

Tn5 lac 삽입으로 채소입고병원균에 길항력이 약화된 T-67 및 고추역병균과 참깨역병균에 길항력이 약화된 T-81의 Tn5 lac 유전자 일부와 오른쪽 말단에 있는 길항관련 유전자의 flanking sequence가 cloning된 pAG67 및 pAG81 clone을 선발하였고, pAG67 및 pAG81 clone된 길항관련 유전자의 flanking sequence를 야생 길항균 Pseudomonas maltophilia B-14의 DNA를 probe로 사용하여 Southern hybridization으로 확인하였으며, 제한효소 지도를 작성하여 8Kb 및 4Kb 크기의 flanking sequence가 cloning되었음을 확인하였다. pAG6 및 pAG81의 flanking sequence를 EcoRi-BglII와 EcoRI-MpaI으로 분리하여 유전자 은행으로부터 길항관련 유전자가 cloning된 cosmid clone 7개주를 선발하였다.

• Applied Biological Chemistry
• /
• v.35 no.5
• /
• pp.361-366
• /
• 1992

The antagonistic bacteria, showing distinguished effect against Fusarium oxysporum and Rhizoctonia solani were isolated from the rhizosphares of horticultural plants and identified as Bacillus subtilis. The strains were studied for their chracteristics of biochemistry, physiology, antagonistic effect against plant pathogenic fungi, and growth promoting effect on horticultural plants. The Bacillus thuringiensis(BT) HD-1 toxin gene was introduced into these B. subtilis. The BT toxin genes on chromosome of the bacteria were identified by southern blotting, but its proteins were not detected by SDS-PAGE. These transformed bacteria showed growth promoting effect and showed also insecticidal and antagonistic effects against Bombix mori and fungi F. oxysporum and R. solani but not against nematode Bursaphelenchus xylophilus.

• The Plant Pathology Journal
• /
• v.25 no.4
• /
• pp.389-399
• /
• 2009

A group of beneficial plant bacteria has been shown to increase crop growth referring to as plant growth-promoting rhizobacteria (PGPR). PGPR can decrease plant disease directly, through the production of antagonistic compounds, and indirectly, through the elicitation of a plant defense response termed induced systemic resistance (ISR). While the mechanism of PGPR-elicited ISR has been studied extensively in the model plant Arabidopsis, it is less well characterized in crop plants such as pepper. In an effort to better understand the mechanism of ISR in crop plants, we investigated the induction of ISR by Bacillus cereus strain BS107 against Xanthomonas axonopodis pv. vesicatoria in pepper leaves. We focused on the priming effect of B. cereus strain BS107 on plant defense genes as an ISR mechanism. Of ten known pepper defense genes that were previously reported to be involved in pathogen defense signaling, the expression of Capsicum annum pathogenesis-protein 4 and CaPR1 was systemically primed by the application of strain BS107 onto pepper roots confirming by quantitative-reverse transcriptase PCR. Our results provide novel genetic evidence of the priming effect of a rhizobacterium on the expression of pepper defense genes involved in ISR.

• Journal of Microbiology and Biotechnology
• /
• v.27 no.10
• /
• pp.1727-1735
• /
• 2017

Hepatitis E virus (HEV) infections cause epidemic or sporadic acute hepatitis, which are mostly self-limiting. However, viral infection in immunocompromised patients and pregnant women may result in serious consequences, such as chronic hepatitis and liver damage, mortality of the latter of which reaches up to 20-30%. Type I interferon (IFN)-induced antiviral immunity is known to be the first-line defense against virus infection. Upon HEV infection in the cell, the virus genome is recognized by pathogen recognition receptors, leading to rapid activation of intracellular signaling cascades. Expression of type I IFN triggers induction of a barrage of IFN-stimulated genes, helping the cells cope with viral infection. Interestingly, some of the HEV-encoded genes seem to be involved in disrupting signaling cascades for antiviral immune responses, and thus crippling cytokine/chemokine production. Antagonistic mechanisms of type I IFN responses by HEV have only recently begun to emerge, and in this review, we summarize known HEV evasion strategies and compare them with those of other hepatitis viruses.

• Korean Journal Plant Pathology
• /
• v.10 no.1
• /
• pp.39-46
• /
• 1994

Pseudomonas fluorescens Biovar III strains S-2 antagonistic to Rhizoctonia solani was subjected to Tn5 mutagenesis by the transposon vector pGS9. Ampicillin and kanamycin resistant (Ampr, Kmr) transconjugants were recovered at a frequency of 1.3$\times$10-7 per initial recipient cell, when recipient cells were washed twice in TE buffer before conjugation. Of the ca. 3000 transconjugants, a frequency of noninhibitory (Inh-), nonfluorescent (Flu-) and auxotorphic (Pro-) mutants were 0.27%, 0.47% and 0.40%, respectively. In these mutants, all Inh- mutants showed the same colony morphology as wild type, whereas all Flu- and Pro- mutants inhibited the growth of R. solani. These mutants were also susceptible to chloramphenicol, indicating only the Tn5 element, except for parts of pGS9, was integrated into the recipient genome. In a Southern blot analysis, the Tn5 element inserted into one site on the chromosome for each of the chosen mutants. However, Tn5 insertion sites of Inh-, and Pro- mutants were differed in each other. These indicate that the genes essential for R. solani inhibition, fluorescent production and auxotrophic are chromosomally located, but not linked to each other.

• Korean Journal of Microbiology
• /
• v.49 no.3
• /
• pp.286-291
• /
• 2013

Soybean pastes with 8% (w/w) salinity were prepared instead of soybean paste with 14% (w/w) salinity to meet the growing demands of Korean's low sodium diet. After aging, white films had appeared on the surface of all low-salted soybean pastes [8% (w/w) salinity] unlike high-salted soybean pastes [14% (w/w) salinity]. All of eight microbes isolated from the surface film were identified as Pichia kudriavzevii. Eleven Bacillus strains with good characteristics of fermentation were isolated from traditionally fermented soybean pastes in order to preserve their unique flavors and aromas after aging, and as a result of analyzing the biochemical characteristics and 16S rRNA sequences, those were identified as B. subtilis, B. licheniformis, and B. methylotrophicus. All of the Bacillus isolates had antagonistic activities against 8 isolates of the film-forming yeasts and harbored the genes for synthesis of antimicrobial surfactants including lichenysin and/or surfactin.

• The Plant Pathology Journal
• /
• v.22 no.4
• /
• pp.323-328
• /
• 2006

Serratia marcescens W1, isolated from cucumber-cultivated soil in Suwon, Korea, evidenced profound antifungal activity and produced the extracellular hydrolytic enzymes, chitinase and protease. In order to isolate the antifungal genes from S. marcescens W1, a cosmid genomic library was constructed and expressed in Escherichia coli. Transformants exhibiting chitinase and protease expression were selected, as well as those transformants evidencing antifungal effects against the rice blast fungus, Magnaporthe grisea, and the cucumber leaf spot fungus, Cercospora citrullina. Cosmid clones expressing chitinase or protease exerted no inhibitory effects against the growth of fungal pathogens. However, two cosmid clones evidencing profound antifungal activities were selected for further characterization. An 8.2 kb HindIII fragment from these clones conditioned the expression of antagonistic activity, and harbored seven predicted complete open reading frames(ORFs) and two incomplete ORFs. The deduced amino acid sequences indicated that six ORFs were highly homologous with genes from S. marcescens generating pyrroloquinoline quinone(PQQ). Only subclones harboring the full set of pqq genes were shown to solubilize insoluble phosphate and inhibit fungal pathogen growth. The results of this study indicate that the functional expression of the pqq genes of S. marcescens W1 in E. coli may be involved in antifungal activity, via as-yet unknown mechanisms.

• Journal of Microbiology
• /
• v.43 no.3
• /
• pp.308-312
• /
• 2005

The global RNA transcription profiles of Bacillus lentimorbus WJ5 under an in vitro co-culture with Colletotrichum gloeosporioides were analyzed in order to study the antagonistic bacteria-fungi interactions. Using a filter membrane system, B. lentimorhus WJ5 was exposed to the spores of C. gloeosporioides at the late exponential stage. The transcription profiles of the B. lentimorhus WJ5, both with and without a challenge from C. gloeosporioides, were analyzed using custom DNA chips containing 2,000 genome fragments. A total of 337 genes were expressed, with 87 and 47 up- and down-regulated, respectively. Of these, 12 genes, which were involved in central carbon metabolisms, and 7 from minor catabolism were relatively highly up-regulated (> 10 fold) and down-regulated (< 0.2 fold), respectively. Nine genes, which were thought to be related to the antifungal activity, were also up-regulated, but their levels were not so high (2.0 - 9.7 folds). From the results, during the early stage of the co-culture of B. lentimorbus WJ5 and C. gloeosporioides, nutrient competition seemed to occur; therefore, the genes from central carbon metabolisms could be up-regulated, while those from minor catabolism could be down-regulated.