• The Plant Pathology Journal
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• v.28 no.4
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• pp.439-445
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• 2012

The chitinase producing Lysobacter enzymogenes C-3 has previously been shown to suppress plant pathogens in vitro and in the field, but little is known of the regulation of chitinase production, or its role in antimicrobial activity and biocontrol. In this study, we isolated and characterized chitinase-defective mutants by screening the transposon mutants of L. enzymogenes C-3. These mutations disrupted genes involved in diverse functions: glucose-galactose transpoter (gluP), disulfide bond formation protein B (dsbB), Clp protease (clp), and polyamine synthase (speD). The chitinase production of the SpeD mutant was restored by the addition of exogenous spermidine or spermine to the bacterial cultures. The speD and clp mutants lost in vitro antifungal activities against plant fungal pathogens. However, the gluP and dsbB mutants showed similar antifungal activities to that of the wild-type. The growth of the mutants in nutrient rich conditions containing chitin was similar with that of the wild-type. However, growth of the speD and gluP mutants was defective in chitin minimal medium, but was observed no growth retardation in the clp and dsbB mutant on chitin minimal medium. In this study, we identified the four genes might be involved and play different role in the production of extracellular chitinase and antifungal activity in L. enzymogenes C-3.

• Journal of Physiology & Pathology in Korean Medicine
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• v.16 no.6
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• pp.1184-1189
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• 2002

Allii sativi Bulbus(garlic) have been shown to possess medicinal value, in particular, antimicrobial activity. In this study, we compared the efficacy on some pathogenic bacteria and fungus among several different extracts(water, hexane, ethyl acetate, methanol, chloroform) of Allii sativi Bulbus. Animal pathogenic bacteria and fungus(S. gallinarium: KCTC 2441, S. flexneri: KCTC 2361, E. cloacae: KCTC 2006, K. pneumonia: KCTC 2208, C. albicans: KCTC 1940) were used to test by measurement of minimum inhibitory concentrations(MIC) and disc diffusion. Allii sativi Bulbus were cut and mixed with water at 37℃ about 24 h and filtered, and several different solvents(hexane, chloroform, ethyl acetate, methanol) were respectively added to separate the fraction of each solvent. The antimicrobial(bacteriocidal) and antifungal effect were apparently shown from water extract, hexane and ethyl acetate extract against using strains(Staphylococcus gallinarium, Shigella flexneri, Enterobacter doacae, Klebsiella pneumonia, Candida albicans). Especially, the water extract showed the superior efficacy. And the clear zone size of water extract (11～27 mm) was greater than that of gentamycin, hexane extract and ethyl acetate extract against S. gallinarium. S. flexneri, K. pneumonia and C. albicans. Minimum inhibitory concentrations(MIC) of water extract appeared to around 2.0～7.5 ㎎/㎖ against S. gallinarium, S. flexneri, E. cloacae and K. pneumonia. The greater activity was shown by water extract because the MIC of water extract for C. albicans observed in very low concentration(<1.0 ㎎/㎖) compared to hexane(5.0 ㎎/㎖) and ethyl acetate(10.0 ㎎/㎖). Therefore, these results exhibited that water extract of Allii sativi Bulbus have stronger antimicrobial activity than hexane and ethyl acetate extract, and may be useful as topical medicine of superficial infections causing C. albicans as well as antifungal agents.

• The Plant Pathology Journal
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• v.36 no.3
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• pp.231-243
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• 2020

Rice blast, caused by Magnaporthe oryzae, is one of the most destructive rice diseases worldwide. The aim of this study was to screen bacterial isolates to efficiently prevent the occurrence of rice blast. A total of 232 bacterial isolates were extracted from nonrhizospheric rice soil and were screened for antifungal activity against M. oryzae using a leaf segment assay. Strains S170 and S9 showed significant antagonistic activity against M. oryzae in vitro and in leaf disk assays, and controlled M. oryzae infection under greenhouse conditions. The results showed that strains S170 and S9 could effectively control rice leaf blast and panicle neck blast after five spray treatments in field. This suggested that the bacterial strains S170 and S9 were valuable and promising for the biocontrol of rice disease caused by M. oryzae. Based on 16S rDNA, and gyrA and gyrB gene sequence analyses, S170 and S9 were identified as Bacillus amyloliquefaciens and B. pumilus, respectively. The research also demonstrated that B. amyloliquefaciens S170 and B. pumilus S9 could colonize rice plants to prevent pathogenic infection and evidently suppressed plant disease caused by 11 other plant pathogenic fungi. This is the first study to demonstrate that B. amyloliquefaciens and B. pumilus isolated from nonrhizospheric rice soil are capable of recolonizing internal rice stem tissues.

• The Korean Journal of Pesticide Science
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• v.14 no.4
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• pp.421-426
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• 2010

Many bacterial strains inhabit strong saline condition, such as tidal mudflat and salted seafoods, were identified and reported for the proposed protease activities and salt resistance; however antifungal activities against plant fungal pathogen have not well been studied until now. In this study, primary screening was performed for the isolation of promising strains against major plant pathogens like Sclerotinia sclerotiorum, Fusarium oxysporum, Phytophthora capsici, Botrytis cineria, Collectotrichum acutatum and Pythium ultimum. Totally 423 bacterial strain were isolated from laboratory media which was based on different morphological characteristics and all the strains were dual cultured against major fungal pathogens on PDA, finally 40 strains were selected as antifungal bacterial strain and identified by fatty acid phylogenic difference analysis from MIDI shorlock gas chromatography system. As a result, antifungal strains from tidal mudflat were 10 species of 6 genus. Paenibacillus macerans was dominant species; 5 strains among the 17 isolates from tidal mudflat. Antifungal strains from salted seafoods were 7 species of 3 genus and Bacillus atrophaeus was dominant species; 12 strains among the 23 isolates from salted fishes.

• Journal of Food Hygiene and Safety
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• v.8 no.3
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• pp.141-145
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• 1993

Thirty nine kinds of Korean herb drugs have screened for antimicrobial activity of some pathogenic microorganisms. It was revealed that some of hot water extracts from herb drugs showed antimicrobial activity in one or more strain of pathogenic microorganisms. Phellodendron amurense and Coptis chinensis inhibited growth of Staphylococcus aureus. Rubus coreanus showed antibacterial activity in Staphylococcus aureus and Pseudomonas aeruginosa. Citrus unshill inhibited growth of Escherichia coli and Cornus officinalis showed antibacterial activity in E. coli and Pseudomonas aeruginosa. Dioscorea battltas and Cinnamomum cassia showed antibacterial activity in Pseodomonas aeruginosa. And also, ScutelJa baicaJerrsis inhibited growth of Candida albicanus. Achyranthes japonica and Glycyrrhiza uralensis showed antifungal activity in Aspergillus niger. It was noteworthy that Glycrrhiza uranensis inhibited growth of Staphylococcus aureus, E. coli, Pseudomonas aeruginosa and Aspergillus niger.

• The Plant Pathology Journal
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• v.24 no.1
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• pp.24-30
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• 2008

Colletotrichum gloeosporioides forms an appressorium, a specialized infection structure, to infect its hosts. Among 400 and 600 culture filtrates from fungi and class Actinomycetes, six methanol extracts (A5005, A5314, A5387, A5560, A5597, and A5598) from the class Actinomycetes significantly inhibited appressorium formation in C. gloeosporioides infecting pepper fruits in a dose-dependent manner, while conidial germination was slightly enhanced. Two (A5005 and A5560) of them also exhibited distinctive inhibitory effect on the disease progress of pepper anthracnose. Water fractions of both culture filtrates also specifically inhibited appressorium formation in C. gloeosporioides and pepper anthracnose disease. Inhibition of appressorium formation by culture filtrate of A5005 was partially restored by the exogenous calcium. This results suggests that chemicals within A5005 extents its biological activity through disturbance of intracellular $Ca^{2+}$ regulation during prepenetration morphogenesis by C. gloeosporioides. Together, cell-based and target-oriented screening system used in this study should be applicable for other plant pathogenic fungi prerequisite appressorium formation to infect their hosts.

• Korean Journal of Medicinal Crop Science
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• v.6 no.4
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• pp.277-285
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• 1998

Antifungal activity on major seedborne diasease of crops was screened by the treatment of the extracts from 50 medicinal plants in vitro and in vivo. The extracts of garlic and taxus, Rheum undulatum, Achiranthes japonica, Glycyrrhiza uralensis, Oenothera lamar kiana treated with the blotting filter paper and water agar methods inhibited the growth of Pyricularia oryzae, Alternaria sesamicola, Colletotrichum gloeosporioides, and Alternaria brassicicola among the tested plants. Antifungal activities on infected seeds by soaking methods were shown even at the dilution of the extracts by 10 times. The activity was the highest in soaking seeds at $25^{\circ}C$ for 24 hours. The effect of plant extract on seed germination was not significant as compared with untreated seed. However, early growth of seedling was increased by the treatment of extracts. The extract of taxus slightly inhibited the seed germination of radish and chinese cabbage but those of Achirunthes japonica, Glycyrrhiza uralensis and Oenthfera lamarkiana showed severe damage on the seed germination and early growth of seedling.

• The Korean Journal of Mycology
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• v.18 no.2
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• pp.96-101
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• 1990

This study was conducted to select the promising antifungal microoganisms for biological control of wet bubble, Mycogone perniciosa. Ninty one isolates of fungi, 342 isolates of bacteria, and 556 actinomycetes were isolated from mushroom composts and soils, were subjected to primary screening test on agar medium base for their antimicrobial spectra. Among them, 12 bacteria and 71 actinomycetes were selected. Among the antibiotic producing microoganisms, 5 cultures were selected on the basis their antibiotic activities on casing soil with Benlate nontolerence M. perniciosa. Finally, AJ-117, AJ-136 and AK-139 were selected as microoganism with antifungal activity against two strains of M. perniciosa.

• Journal of Microbiology and Biotechnology
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• v.14 no.1
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• pp.220-223
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• 2004

Club root caused by Plasmodiophora brassicae is found in crucifers. Among the over hundreds of Streptomyces isolated from soil in Korea. One strain showed prominent activity against P. brassicae. The strain was identified based on 16S rDNA sequencing and the morphology by a method of scanning electron microscopy. An active compound in the fermented broth obtained from the strain was separated. Even though the complete assignments of the compound remain for future work, the results regarding the isolation and characterization of the strain with a certain activity against P. brassicae are shown in this paper.

• Korean Journal of Microbiology
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• v.19 no.3
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• pp.108-114
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• 1981

In order to isolate microorganisms which produce antibiotics aganist wheat black rust, some bacteria, molds, and actinomycetes were isolated from soils and screened for the production of antibiptics against wheat black rust. Beacuse wheat black rust-puccinia graminis--is a complete parsitic mold which can't grow in artifical medium, new method for the screening of antibiotic producing microorgsnisms against wheat black rust developed by using live leaves of wheat. With new method, a strain No. $480HS_{20}$ which produces a substnace having strong and Puccinia graminis activity and very narrow antimicrobial spectrum was isolated. the substance produced by the strain No.$480HS_{20}$ had better anti Puccinia graminis activity than any other known antifungal antibotics such as kasurgamycin, balasticidins, actidione, antimycin, ologomycin. And the substance was observed to be very stable at heat and ultraviolet light. The strain was indentified as Bacillus subtilis.