• Journal of Microbiology and Biotechnology
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• v.20 no.11
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• pp.1577-1584
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• 2010

In total, 140 halotolerant bacterial strains were isolated from both the soil of barren fields and the rhizosphere of six naturally growing halophytic plants in the vicinity of the Yellow Sea, near the city of Incheon in the Republic of Korea. All of these strains were characterized for multiple plant growth promoting traits, such as the production of indole acetic acid (IAA), nitrogen fixation, phosphorus (P) and zinc (Zn) solubilization, thiosulfate ($S_2O_3$) oxidation, the production of ammonia ($NH_3$), and the production of extracellular hydrolytic enzymes such as protease, chitinase, pectinase, cellulase, and lipase under in vitro conditions. From the original 140 strains tested, on the basis of the latter tests for plant growth promotional activity, 36 were selected for further examination. These 36 halotolerant bacterial strains were then tested for 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. Twenty-five of these were found to be positive, and to be exhibiting significantly varying levels of activity. 16S rRNA gene sequencing analyses of the 36 halotolerant strains showed that they belong to 10 different bacterial genera: Bacillus, Brevibacterium, Planococcus, Zhihengliuella, Halomonas, Exiguobacterium, Oceanimonas, Corynebacterium, Arthrobacter, and Micrococcus. Inoculation of the 14 halotolerant bacterial strains to ameliorate salt stress (150 mM NaCl) in canola plants produced an increase in root length of between 5.2% and 47.8%, and dry weight of between 16.2% and 43%, in comparison with the uninoculated positive controls. In particular, three of the bacteria, Brevibacterium epidermidis RS15, Micrococcus yunnanensis RS222, and Bacillus aryabhattai RS341, all showed more than 40% increase in root elongation and dry weight when compared with uninoculated salt-stressed canola seedlings. These results indicate that certain halotolerant bacteria, isolated from coastal soils, have a real potential to enhance plant growth under saline stress, through the reduction of ethylene production via ACC deaminase activity.

• Journal of Life Science
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• v.23 no.8
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• pp.1010-1018
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• 2013

The greenhouse whitefly, Bemisia tabaci, is considered one of the most destructive pests of crops. In this study, we aimed to determine the optimal liquid culture conditions in shake flasks for maximal sporulation of Beauveria bassiana M130 using rice bran. The optimal initial pH for the spore production of B. bassiana using extracted rice bran medium was 5.2 and $28^{\circ}C$. The screening in shake flasks of carbon and nitrogen sources resulted in the identification of an optimal medium based on 0.5% $(NH_4)_2SO_4$, with extracted rice bran 8:1. Using this medium, a production level of $2.15{\times}10^9$ spores per ml was obtained after six days from culture inoculation at $28^{\circ}C$ in a rotary shaking incubator at 130 rpm. In addition, the specific activities of extracellular enzymes of chitinase and protease were $4,296{\mu}mol$ and $375{\mu}mol$, respectively. These results suggest that Beauveria bassiana M130 could be a bio-controller for the greenhouse whitefly.

• The Plant Pathology Journal
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• v.31 no.1
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• pp.50-60
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• 2015

The use of novel isolates of Trichoderma with efficient antagonistic capacity against Fusarium oxysporum f. sp. lycopersici (FOL) is a promising alternative strategy to pesticides for tomato wilt management. We evaluated the antagonistic activity of 30 isolates of T. asperellum against 4 different isolates of FOL. The production of extracellular cell wall degrading enzymes of the antagonistic isolates was also measured. The random amplified polymorphic DNA (RAPD) method was applied to assess the genetic variability among the T. asperellum isolates. All of the T. asperellum isolates significantly reduced the mycelial growth of FOL isolates but the amount of growth reduction varied significantly as well. There was a correlation between the antagonistic capacity of T. asperellum isolates towards FOL and their lytic enzyme production. Isolates showing high levels of chitinase and ${\beta}$-1,3-glucanase activities strongly inhibited the growth of FOL isolates. RAPD analysis showed a high level of genetic variation among T. asperellum isolates. The UPGMA dendrogram revealed that T. asperellum isolates could not be grouped by their antagonistic behavior or lytic enzymes production. Six isolates of T. asperellum were highly antagonistic towards FOL and potentially could be used in commercial agriculture to control tomato wilt. Our results are consistent with the conclusion that understanding the genetic variation within Trichoderma isolates and their biochemical capabilities are required for the selection of effective indigenous fungal strains for the use as biocontrol agents.

• Mycobiology
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• v.40 no.2
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• pp.111-116
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• 2012

Ten strains of the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana were evaluated to find the most effective strain for optimization studies. The first criterion tested for strain selection was the mortality (> 50%) of Spodoptera litura larvae after inoculation of the fungus for 4 days. Results on several bioassays revealed that B. bassiana BNBCRC showed the most virulence on mortality S. litura larvae (80% mortality). B. bassiana BNBCRC also showed the highest germination rate (72.22%). However, its conidia yield ($7.2{\times}10^8$ conidia/mL) was lower than those of B. bassiana B 14841 ($8.3{\times}10^8$ conidia/mL) and M. anisopliae M6 ($8.2{\times}10^8$ conidia/mL). The highest accumulative radial growth was obtained from the strain B14841 (37.10 mm/day) while the strain BNBCRC showed moderate radial growth (24.40 mm/day). M. anisopliae M6 possessed the highest protease activity (145.00 mU/mL) while M. anisopliae M8 possessed the highest chitinase activity (20.00 mU/mL) during 96~144 hr cultivation. Amongst these criteria, selection based on virulence and germination rate lead to the selection of B. bassiana BNBCRC. B. bassiana B14841 would be selected if based on growth rate while M. anisopliae M6 and M8 possessed the highest enzyme activities.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.1
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• pp.77-83
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• 1999

Molecular biological techniques that recently developed, have made it possible to realize some of new attempts in the research field of rumen microbiology. Those are 1) cloning of genes from rumen microorganisms mainly in E. coli, 2) transformation of rumen bacteria and 3) ecological analysis with nonculturing methods. Most of the cloned genes are for polysaccharidase enzymes such as endoglucanase, xylanase, amylase, chitinase and others, and the cloning rendered gene structural analyses by sequencing and also characterization of the translated products through easier purification. Electrotransformation of Butyrivibrio fibrisolvens and Prevotella ruminicola have been made toward the direction for obtaining more fibrolytic, acid-tolerant, depoisoning or essential amino acids-producing rumen bacterium. These primarily required stable and efficient gene transfer systems. Some vectors, constructed from native plasmids of rumen bacteria, are now available for successful gene introduction and expression in those rumen bacterial species. Probing and PCR-based methodologies have also been developed for detecting specific bacterial species and even strains. These are much due to accumulation of rRNA gene sequences of rumen microbes in databases. Although optimized analytical conditions are essential to reliable and reproducible estimation of the targeted microbes, the methods permit long term storage of frozen samples, providing us ease in analytical work as compared with a traditional method based on culturing. Moreover, the methods seem to be promissing for obtaining taxonomic and evolutionary information on all the rumen microbes, whether they are culturable or not.

• Microbiology and Biotechnology Letters
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• v.46 no.1
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• pp.68-76
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• 2018

Actinobacterial strains isolated from Cow feces were studied for their antifungal attributes against phytopathogens and industrially important enzymes. A total of 30 Actinobacterial strains were obtained from 10 samples of cow feces. All the strains were belonging to the genera Streptomyces on the basis of morphological and chemotaxonomic analysis. During preliminary screening, out of 30 strains, 15 strains (50%) showed antifungal activity against five fungal phytopathogens including Aspergillus niger, Fusarium solani, Fusarium oxysporum, Macrophomina phaseolina and Rhizoctonia solani. While, isolate GBTCF-26 was found to be most active against R. solani with 62.2% inhibition of fungal mycelium, GBTCF-09 was prominent against F. solani and F. oxysporum with percent inhibition of 61.1% and 58.8%, respectively. Out of 30 strains, 19 (63.3%), 16 (53.3%), 11 (36.7%), 10 (33.3%), 4 (13.3%) and 8 (26.7%) strains were producing amylase, caseinase, gelatinase, lipase, chitinase and cellulose, respectively. The selected strains, GBTCF-09, GBTCF-21 and GBTCF-26, were identified as Streptomyces sp. on the basis of their 16S rDNA sequence. The study supports the idea that the Actinobacteria from unique niches (Cow feces) possess the production potential of industrially important enzymes including bioactive molecules.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1998.11a
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• pp.172-173
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• 1998

A research collection of Pseudomons solanacearum bacteria, a pathogen causing ‘bacteria wilt’ disease of more than 265 plant species, represented for northern provinces of Vietnam has recently been established and was saved for examination of antifungal activity in their culture fluids. All strains used in this work have been isolated from infected tomato, potato, and groundnut collected from production fields and they express different levels of virulence on their host plants. Cell-free culture fluids of these strains were tested for antifungal activity (to inhibit growth of mycelium and to destroy germination tube of fungal spores) on a number of fungi that either infect or associate with vegetable crops of Solanaceae family (tomato, potato, pepers...), fruit plants (banana), and even well-known by Vietnamese traditional medicine herbal plants belonging to Trifoliatus, Schefflera, Homalomena and Panax genera (Araliaceae family) of which roots are used as a resource of the herbal material. The antifungal activity was found in nearly all strains tested. Result of study on chitin, CMC, tween 80 and casein degradation abilities of the latter suggested that antifungal activity of positively-found strains may be due to their ability of extracelluar chitinase's excretion that destroy fungal cell wall.

• The Korean Journal of Mycology
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• v.44 no.1
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• pp.36-47
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• 2016

This study was conducted to evaluate five different strains of rhizobacterial isolates viz. PA1, PA2, PA4, PA5 and PA12 for biological control against Colletotrichum acutatum, C. coccodes, C. gloeosporioides, C. dematium, Botrytis cinerea, Rhizoctonia solani, Sclerotinia minor and Fusarium sp. In vitro inhibition assay was performed on three different growth mediums, potato dextrose agar (PDA), tryptic soy agar (TSA), and PDA-TSA (1:1 v/v) for the selection of potential antagonistic isolates. According to the result, isolate PA2 showed the highest inhibitory effect with 65.5% against C. coccodes on PDA and with 96.5% against S. minor on TSA. However, the same isolate showed the highest inhibition with 58.5% against C. acutatum on PDA-TSA. In addition, an in vivo experiment was performed to evaluate these bacterial isolates for biological control against fungal pathogens. Plants treated with bacteria were analyzed with phytopathogens and plants inoculated with phytopathogens were treated with isolates to determine the biological control effect against fungi. According to the result, all five isolates tested showed inhibitory effects against phytopathogens at various levels. Mode of action of these rhizobacterial isolates was evaluated with siderophore production, protease assay, chitinase assay and phosphate solubilizing assay. Bacterial isolates were identified by 16S rDNA sequencing, which showed that isolates PA1 and PA2 belong to Bacillus subtilis, whereas, PA4, PA5, and PA12 were identified as Bacilus altitudinis, Paenibacillus polymyxa and Bacillus amyloliquefaciens, respectively. Results of the current study suggest that rhizobacterial isolates can be used for the plant growth promoting rhizobacteria (PGPR) effect as well as for biological control of various phytopathogens.

• Korean Journal of Microbiology
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• v.48 no.1
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• pp.16-21
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• 2012

Since many pesticides cause various health and environmental problems, alternative measures to replace them are needed, and the bacteria producing the antifungal substances can be one of them. In this study, several rhizobacteria were isolated and their antifungal activities against some important plant pathogenic fungi were examined. Pseudomonas otitidis TK1 and Paenibacillus peoriae RhAn32 inhibited the growth of Fusarium oxysporum f. sp. niveum and F. oxysporum f. sp. lycopersici by 49.8% and 45.6%, and 45.1% and 48.3%, respectively compared to those of the control. P. peoriae RhAn32 also decreased the growth of F. oxysporum f. sp. raphani by 37.5%. This growth inhibition might be due to the production of antifungal substances, such as siderophore, hydrogen cyanide and chitinase, which were produced by these rhizobacteria. P. otitidis TK1 also produced plant growth hormones indole acetic acid and indole butyric acid at $293.41{\mu}g/mg$ protein and $418.53{\mu}g/mg$ protein, respectively. When P. otitidis TK1 and B. cereus TK2 were inoculated together with F. oxysporum f. sp. lycopersici to the 4 weeks grown tomato seedlings and incubated additional 8 weeks, the stem lengths of tomato increased up to 45.7% and 55.3% and root lengths were raised to 64.9% and 60.8%, respectively than those of the control group. The wet weights increased by 118% and 182%, respectively compared to the control group.

• Korean Journal of Food Science and Technology
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• v.21 no.1
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• pp.37-44
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• 1989

This study aims at producing red pigment effectively by using protoplast fusion. Auxotrophic mutants of M. anka, $4478-27-37(Thi^-,\;Met^-),\;4478-27-62(Thi^-,\;Arg^-)$ were derived from M. anka, 4478-27. M. anka, $6540-185-24\;(Pan^-,\;Leu^-)$ and M. anka, $6540-185-72\;(Arg^-)$ were derived from M. anka, 6540-185. The optimal conditions of protoplast fromation were at time by using mixtures of chitinase (100mg/ml), cellulase (5mg/ml) and ${\beta}-glucuronidase\;(5mg/ml)$. The protoplast of those auxotrophic mutants were fused effectively, in the solution of 30% PEG $6,000,001M-CaCl_2$, 0.05M-glycine, pH 6.0. Fusion frequencies were 0.70%-0.85%. Fusants, No. 14 and 42 produced highest red pigment among them.