• Journal of the Korean Applied Science and Technology
• /
• v.39 no.6
• /
• pp.831-838
• /
• 2022

An auxin-producing bacteria, KSD16, KSD33, and KSD36 were isolated from agricultural soil. The strain KSD16, KSD33, and KSD36 was classified as a strain of Arthrobacter sp. based on phylogenetic analysis of 16S rRNA gene. The isolated KDS16, KDS33, and KSD36 was confirmed to produce indole-3-acetic acid (IAA), which is one of the auxin hormones. When the concentration of IAA was assessed the maximum concentration of IAA, 206.62 mg L^-1, was detected from the culture broth incubated in R2A medium containing 0.1% L-tryptophan for 48 h at 28 ℃. To study the effect of IAA producing bacteria on germination rate, seeds of Mung bean were prepared for each treatment. KSD16, KSD33, and KSD36 showed significant increase in root length and number of adventitious roots than the controls. To investigate the growth-promoting effects on the crops, Arthrobacter species were placed in water cultures and seed pots of mung beans. In consequence, the seed germination of mung beans was 73.4% higher than the control.

• Journal of Environmental Science International
• /
• v.32 no.11
• /
• pp.777-788
• /
• 2023

Potato common scab disease is caused by pathogens belonging to Streptomyces spp. and results in a serious yield loss worldwide. Despite decades of research aimed at disease management, a definitive control method remains undiscovered. This study aims to explore the correlation between the C/N ratio and urea application with potato common scab pathogen dynamics and disease severity. We applied sawdust with a high C/N ratio and urea into the soil prior to potato cropping, both in pot and field experiments. Disease severity assessments and quantification of the TxtB gene were conducted at the harvest stage. Furthermore, culture experiments were performed to assess the direct impact of urea on the pathogen. Our findings revealed that higher disease severity was correlated with a high C/N ratio application and pathogenic gene quantity. Urea exhibited a direct influence on S. scabiei activity, reducing the disease severity in pot experiments. However, the effects of urea application on disease suppression in the conductive field were inconclusive. Although the results of urea application experiments displayed inconsistencies between pot and field trials, urea worked as the control to suppress S. scabiei activity. Further investigations are needed under various field conditions to confirm these findings.

• Journal of Radiation Industry
• /
• v.17 no.2
• /
• pp.183-190
• /
• 2023

The global problem of handling radioactive materials is facing limitations. Eco-friendly bioremediation methods using microorganisms are being studied. This study was conducted to screen cesium-resistant microbial strains. M1 strain was selected from the soil sample by enriched culture in R2A medium containing 100 mM CsCl. In liquid medium containing above 40 mM of CsCl, the growth of M1 was inhibited in a concentration-dependent manner. Otherwise, M1 can survive up to 80mM CsCl in solid medium although the growth rate was slow and colony size was small. M1 strain was genetically identified as a strain of the genus Acinetobacter through 16S rRNA sequencing, and radiation resistance (D10 value) of M1 was found to be 0.307 kGy. These results showed that M1 strain is highly resistant to cesium and can grow in radiation environment. It was considered that M1 strain is useful in the field of biological decontamination of cesium.

• Journal of Microbiology and Biotechnology
• /
• v.34 no.5
• /
• pp.1029-1039
• /
• 2024

This study explores beneficial bacteria isolated from the roots and rhizosphere soil of Khao Rai Leum Pua Phetchabun rice plants. A total of 315 bacterial isolates (KK001 to KK315) were obtained. Plant growth-promoting traits (phosphate solubilization and indole-3-acetic acid (IAA) production), and antimicrobial activity against three rice pathogens (Curvularia lunata NUF001, Bipolaris oryzae 2464, and Xanthomonas oryzae pv. oryzae) were assessed. KK074 was the most prolific in IAA production, generating 362.6 ± 28.0 ㎍/ml, and KK007 excelled in tricalcium phosphate solubilization, achieving 714.2 ± 12.1 ㎍/ml. In antimicrobial assays using the dual culture method, KK024 and KK281 exhibited strong inhibitory activity against C. lunata, and KK269 was particularly effective against B. oryzae. In the evaluation of antimicrobial metabolite production, KK281 and KK288 exhibited strong antifungal activities in cell-free supernatants. Given the superior performance of KK281, taxonomically identified as Bacillus sp. KK281, it was investigated further. Lipopeptide extracts from KK281 had significant antimicrobial activity against C. lunata and a minimum inhibitory concentration (MIC) of 3.1 mg/ml against X. oryzae pv. oryzae. LC-ESI-MS/MS analysis revealed the presence of surfactin in the lipopeptide extract. The crude extract was non-cytotoxic to the L-929 cell line at tested concentrations. In conclusion, the in vitro plant growth-promoting and disease-controlling attributes of Bacillus sp. KK281 make it a strong candidate for field evaluation to boost plant growth and manage disease in upland rice.

• The Plant Pathology Journal
• /
• v.40 no.4
• /
• pp.346-357
• /
• 2024

This study was carried out to screen the antifungal activity against Colletotrichum acutatum, Colletotrichum dematium, and Colletotrichum coccodes. Bacterial isolate GP-P8 from pepper soil was found to be effective against the tested pathogens with an average inhibition rate of 70.7% in in vitro dual culture assays. 16S rRNA gene sequencing analysis result showed that the effective bacterial isolate as Bacillus siamensis. Biochemical characterization of GP-P8 was also performed. According to the results, protease and cellulose, siderophore production, phosphate solubilization, starch hydrolysis, and indole-3-acetic acid production were shown by the GP-P8. Using specific primers, genes involved in the production of antibiotics, such as iturin, fengycin, difficidin, bacilysin, bacillibactin, surfactin, macrolactin, and bacillaene were also detected in B. siamensis GP-P8. Identification and analysis of volatile organic compounds through solid phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS) revealed that acetoin and 2,3-butanediol were produced by isolate GP-P8. In vivo tests showed that GP-P8 significantly reduced the anthracnose disease caused by C. acutatum, and enhanced the growth of pepper plant. Reverse transcription polymerase chain reaction analysis of pepper fruits revealed that GP-P8 treated pepper plants showed increased expression of immune genes such as CaPR1, CaPR4, CaNPR1, CaMAPK4, CaJA2, and CaERF53. These results strongly suggest that GP-P8 could be a promising biocontrol agent against pepper anthracnose disease and possibly a pepper plant growth-promoting agent.

• Journal of Environmental Health Sciences
• /
• v.50 no.4
• /
• pp.274-281
• /
• 2024

Background: One of the major causes of pathogenic E. coli is the feces of infected livestock, and the management of the livestock environment is necessary to prevent pathogenic E. coli. Objectives: The prevalence of pathogenic E. coli was identified from livestock environments, and the molecular characteristics and antibiotic resistance profiles of the isolated pathogenic E. coli strains were analyzed. Methods: In 2022 and 2023, nine points of livestock houses at sites in Chungcheongnam-do Province were selected, and 100 cow feces or soil samples around the livestock houses were collected once per month. Pathogenic E. coli was isolated by selective culture and identified using multiplex PCR. Antibiotic resistance was tested on the isolated strains by using VITEK-2, and candidate strains were selected to perform 16s rRNA sequencing and phylogenetic analysis. Results: A total of 100 samples were tested, and 60 pathogenic E. coli strains were isolated. Of these, 45 and 15 isolates were determined to be single and hybrid pathogenic E. coli , respectively. Among the 15 hybrid pathogenic E. coli strains, eight, five, and two strains were respectively identified as EHEC/ETEC, EHEC/EPEC, and EHEC/ETEC/EPEC hybrids. All 45 isolates showed resistance to at least one antibiotic, and they were susceptible to cefotaxime, amikacin, nalidixic acid, and ciprofloxacin. The highest resistance was against cefalotin, tetracyclin, and ampicillin (20.0%~58.3%). The 16s rRNA sequences of candidate isolates revealed nucleotide sequence identities of 99.1% to 100%. Conclusions: In order to manage pathogenic E. coli from the One Health animal environment perspective, the characteristics of the occurrence of pathogenic E. coli from the livestock environment and molecular biology and antibiotic resistance to isolated strains were analyzed. In order to prevent and manage the occurrence of pathogenic E. coli, these monitoring studies must be continuously conducted.

• Journal of Microbiology and Biotechnology
• /
• v.34 no.8
• /
• pp.1671-1679
• /
• 2024

Aspergillus flavus, the primary mold that causes food spoilage, poses significant health and economic problems worldwide. Eliminating A. flavus growth is essential to ensure the safety of agricultural products, and extracellular compounds (ECCs) produced by Bacillus spp. have been demonstrated to inhibit the growth of this pathogen. In this study, we aimed to identify microorganisms efficient at inhibiting A. flavus growth and degrading aflatoxin B₁. We isolated microorganisms from soil samples using a culture medium containing coumarin (CM medium) as the sole carbon source. Of the 498 isolates grown on CM medium, only 132 bacterial strains were capable of inhibiting A. flavus growth. Isolate 3BS12-4, identified as Bacillus siamensis, exhibited the highest antifungal activity with an inhibition ratio of 43.10%, and was therefore selected for further studies. The inhibition of A. flavus by isolate 3BS12-4 was predominantly attributed to ECCs, with a minimum inhibitory concentration and minimum fungicidal concentration of 0.512 g/ml. SEM analysis revealed that the ECCs disrupted the mycelium of A. flavus. The hydrolytic enzyme activity of the ECCs was assessed by protease, β-1,3-glucanase, and chitinase activity. Our results demonstrate a remarkable 96.11% aflatoxin B1 degradation mediated by ECCs produced by isolate 3BS12-4. Furthermore, treatment with these compounds resulted in a significant 97.93% inhibition of A. flavus growth on peanut seeds. These findings collectively present B. siamensis 3BS12-4 as a promising tool for developing environmentally friendly products to manage aflatoxin-producing fungi and contribute to the enhancement of agricultural product safety and food security.

• Korean Journal of Soil Science and Fertilizer
• /
• v.23 no.1
• /
• pp.53-59
• /
• 1990

The antagonistic fluorescent pseudomonas, which was isolated from continuous cropping rhizosphere of pepper and cucumber, was identified as Pseudomonas fluorescens (P.f.). For further study, transformant was derived from the isolated P.f. after spontaneous mutation to give antibiotic resistance to nalidixic acid and rifampicin as marked strain. Both P.f. and transformant strains were used for this study and the results obtained were summarized as follows. 1. One of the most effective antagonistic strain, KR164, was selected against F. solani, F. oxysporum, R. solani and this strain was identified and classified as Pseudomonas fluorescens biotype IV. 2. Transformant, KR1641, was derived from strain KR164 and both strains had the same biological and biochemical characteristics. 3, Mycelial lysis and abnormal mycelia of plant pathogenic fungi were microscopically observed after simultaneous culture of fungus and given bacterial strain. 4. The length of chinese cabbage to the autolyzed became longer with given bacterial strain in dark culture. 5. Percentage of germination, number of leaves, length of height, and length of root in chinese cabbage in pot experiment were improved by inoculation of given bacterial strain. 6. The number of given bacterial strain kept generally stable until 34 days after inoculation of itself in pot experiment. Inoculation of given bacterial strain did affect the number of plant disease fungi to be decreased but did not affect the number of other bacteria, Bacillus, in pot experiment.

• Korean Journal of Soil Science and Fertilizer
• /
• v.15 no.4
• /
• pp.270-276
• /
• 1982

Water culture experiment with mulberry (Morus alba L.)was carried out to investigate the ionic composition in the exudate and the ionic content in the organs (leaves, petioles, stem cortex, and roots) of mulberry tree with three different nitrogen sources ($NO_3-N$, $NH_4-N$, and $NH_4NO_3$). 1. Amount of exudate was much lower for $NH_4-N$ than for $NO_3-N$. 2. Total nitrogen content in the exudate was the highest in the NH4-N, the order of 2.2 times than in the $NO_3-N$. However, total nitrogen amount absorbed by tree per hour was proportional with the exudate amount. As the result, total nitrogen amount was higher 1.6 times in $NO_3-N$ ($289.6\;me\;plant^{-1}\;hr^{-1}$ than in $NH_4-N$. 3. Ammonium nitrogen depressed $Ca^{2+}$ uptake critically and even all of the anions, whereas $Mg^{2+}$, $K^+$ and $Na^+$ affected little. 4. Reduction of $NO_3$ may occured both in root and in leaves. 5. Content of cations and anions was highest in petioles, except $Ca^{2+}$ which was highest in leaves. As the result, petioles may be the storage organ of nutrients. 6. By increasing $NH_4-N$, ionic balance (C-A) decreased proportionally. 7. Nutrients amount in the exudate were approximatelly proportional with the amount in the roots. This suggested that roots may be the part diagnosed for nutrients. Being the sum of anions (${\Sigma}A$) higher than that of cations (${\Sigma}C$) in the roots, the ionic balance showed negative value.

• Korean Journal of Soil Science and Fertilizer
• /
• v.7 no.4
• /
• pp.201-207
• /
• 1974

Some effects of nitrogen, phosphorus, potassium and respiratory inhibitor on growth of rice plant and activity of GOT, GPT and peroxidase for the rice root were investigated. Obtained results were summarized as follows: 1. Growth of rice root and plant applied with $NO_3$-N in culture solution was generally increased in the length and weight compared with that of $NH_4$-N plot. On the other hand, the GOT, GPT and peroxidase activity was more increased in the $NH_4$-N plot than in the $NO_3$-N plot. 2. Oxidative power of ${\alpha}$-naphthylamine in rice root was stronger in the $NO_3$-N plot than in the $NH_4$-N plot. 3. When rice plant was cultured in the medium which did not supplied nitrogen, phosphorus or potassium, respectively, GOT activity was more decreased than GPT activity, while peroxidase activity was increased mostly in the potassium-free plot. 4. When rice plant was cultivated in the culture solution added respiratory inhibitor, NaF, plant height was shortened in the order of nitrogen-free > $NH_4$-H > urea-N > $NO_3$-N plot, and GOT and GPT activity was also decreased in the order of nitrogen-free > $NH_4$-N > urea-N > $NO_3$-N plot.