• The Plant Pathology Journal
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• v.38 no.4
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• pp.313-322
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• 2022

Seed-borne pathogens in crops reduce the seed germination rate and hamper seedling growth, leading to significant yield loss. Due to the growing concerns about environmental damage and the development of resistance to agrochemicals among pathogen populations, there is a strong demand for eco-friendly alternatives to synthetic chemicals in agriculture. It has been well established during the last few decades that plant seeds harbor diverse microbes, some of which are vertically transmitted and important for plant health and productivity. In this study, we isolated culturable endophytic bacteria and fungi from soybean seeds and evaluated their antagonistic activities against common bacterial and fungal seed-borne pathogens of soybean. A total of 87 bacterial isolates and 66 fungal isolates were obtained. Sequencing of 16S rDNA and internal transcribed spacer amplicon showed that these isolates correspond to 30 and 15 different species of bacteria and fungi, respectively. Our antibacterial and antifungal activity assay showed that four fungal species and nine bacterial species have the potential to suppress the growth of at least one seed-borne pathogen tested in the study. Among them, Pseudomonas koreensis appears to have strong antagonistic activities across all the pathogens. Our collection of soybean seed endophytes would be a valuable resource not only for studying biology and ecology of seed endophytes but also for practical deployment of seed endophytes toward crop protection.

• Journal of Microbiology
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• v.43 no.1
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• pp.1-10
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• 2005

We isolated and cultured bacteria inhabiting solar saltern ponds in Taean-Gun, Chungnam Province, Korea. All of the isolated 64 strains were found to be moderately halophilic bacteria, growing in a salt range of 2-20 %, with an optimal concentration of 5% salt. Bacterial diversity among the isolated halophiles was evaluated via RFLP analyses of PCR-amplified 16S rDNAs, followed by phylogenetic analysis of the partial 16S rDNA sequences. The combination of restriction enzyme digestions with HaeIII, CfoI, MspI and RsaI generated 54 distinct patterns. A neighbor-joining tree of the partial 16S rDNA sequences resulted in the division of the 64 strains into 2 major groups, 45 strains of ${\gamma}-Proteobacteria$ (70.3%) and 19 strains of Firmicutes (29.7%). The ${\alpha}-Proteobacteria$ and Cytophaga-Flavobacterium-Bacterioides groups, which were repeatedly found to exist in thalassohaline environments, were not represented in our isolates. The ${\gamma}-Proteobacteria$ group consisted of several subgroups of the Vibrionaceae (37.5%), Pseudoalteromonadaceae (10.9%), Halomonadaceae (7.8%), Alteromonadaceae (7.8%), and Idiomarinaceae (6.3%). Members of Salinivibrio costicola (29.7%) were the most predominant species among all of the isolates, followed by Halobacillus treperi (12.5%). Additionally, three new species candidates were found, based on similarities of the 16S rDNA sequences to those of previously published species.

• Food Science and Preservation
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• v.22 no.6
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• pp.920-925
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• 2015

The microbial composition in Nuruk, a Korean cereal fermentation starter, is a critical factor for the quality and organoleptic properties of traditional alcoholic beverages. This study was aimed at monitoring the compositional change and enzyme activity of culturable lactic acid bacteria (LAB) in two types of Nuruk fermented at different temperatures. All culturable LAB were isolated at various time points (0, 3, 6, 10, 20, and 30 days) and identified by 16S rRNA sequencing. In traditional Nuruk type A (TN-A), which was fermented at $36^{\circ}C$, the population of total culturable LAB during the fermentation period was between $10^4$ and $10^5$ log CFU/mL. On the other hand, the LAB population in traditional Nuruk type B (TN-B) fermented at $45^{\circ}C$ (primary fermentation for 10 days) and $35^{\circ}C$ (secondary fermentation for 20 days) was $10^2$ log CFU/mL; however, these bacteria could not be detected after 6 days. Major LAB strains were identified in both Nuruk types: (1) from the MRS-culture of TN-A, Pediococcus pentosaceus at 3-30 days; (2) from MRS-culture of TN-B, P. pentosaceus at 3 days and Enterococcus hirae at 6 days. The protease activities of the dominant LAB isolated from the TN-A and TN-B cultures were within the ranges of 0.64~1.03 mg/mL and 0.74~0.81 mg/mL (tyrosine content), respectively, whereas the ${\alpha}$-amylase activities were 0.75~0.98 mg/mL and 0.78~0.79 mg/mL (amylose content), respectively.

• Journal of Microbiology and Biotechnology
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• v.17 no.9
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• pp.1558-1562
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• 2007

To elucidate the influence of pipe materials on the VBNC (viable but nonculturable) state and bacterial numbers in drinking water, biofilm and effluent from stainless steel, galvanized iron, and polyvinyl chloride pipe wafers were analyzed. Although no HPC (heterotrophic plate count) was detected in the chlorinated influent of the model system, a DVC (direct viable count) still existed in the range between 3- and 4-log cells/ml. Significantly high numbers of HPC and DVC were found both in biofilm and in the effluent of the model system. The pipe material, exposure time, and the season were all relevant to the concentrations of VBNC and HPC bacteria detected. These findings indicate the importance of determining the number of VBNC cells and the type of pipe materials to estimate the HPC concentration in water distribution systems and thus the need of determining a DVC in evaluating disinfection efficiency.

• Korean Journal of Microbiology
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• v.37 no.1
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• pp.85-91
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• 2001

Biological treatment of benzene and toluene contaminated soil was investigated in laboratory microcosm of 16 different types for degrading benzene and toluene by indigenous bacteria. At the experimental conditions of the microcosms fast degrading benzene and toluene, moisture contents were 30% and 60% in a soil gap and content of powdered-activated carbon(PCA) for adhesion of benzene and toluene-degrading bacteria was 1% in total soil mass. At the conclusion of the shifted bacteria community, Case 6 and case 7 were operated until 10 days, and then the total cell number and the number of benzene and toluene degrading bacteria were investigated. The total cell number of Case 6 and Case 7 increased 488 fold and 308 fold of total indigenous cell, respectively. The number of benzene and toluene degrading bacteria increased and maintained the percentages occupied in pre-operating microcosm. Species of benzene and toluene degrading bacteria in microcosm changed from species of Gram negative bacteria to Gram positive bacterial species after soil exposed to benzene and toluene.

• Korean Journal of Microbiology
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• v.50 no.2
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• pp.119-127
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• 2014

The affiliations and physiological characteristics of culturable bacteria isolated from the sediments of Ross Sea, Antarctica were investigated. Sixty-three isolates obtained by cultivation were grouped into 21 phylotypes affiliated with the phyla Actinobacteria and Bacteroidetes and with the classes Alphaproteobacteria and Gammaproteobacteria by phylogenetic analysis of 16S rRNA gene sequences. Based on phylogenetic analysis (<98.65% sequence similarity), approximately 49% of total isolates represented potentially novel species or genus. Among them, extracellular protease, lipase, and exopolysaccharide activities at $10^{\circ}C$ or $20^{\circ}C$ were detected in approximately 46%, 25%, and 32% of the strains, respectively. Forty-three isolates produced at least one type of extracellular material and 21 of them produced at least two extracellular protease, lipase, and/or exopolysaccharides. Our findings indicate that culturable bacterial diversity present within the marine sediments of Ross Sea, Antarctica may contribute to the hydrolysis of the major organic constituents which is closely related with carbon and nitrogen cycling in this environment.

• Journal of Microbiology and Biotechnology
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• v.24 no.5
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• pp.648-660
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• 2014

Doenjang, a traditional Korean fermented soybean paste, is made by mixing and ripening meju with high salt brine (approximately 18%). Meju is a naturally fermented soybean block prepared by soaking, steaming, and molding soybean. To understand living bacterial community migration and the roles of bacteria in the manufacturing process of doenjang, the diversity of culturable bacteria in meju and doenjang was examined using media supplemented with NaCl, and some physiological activities of predominant isolates were determined. Bacilli were the major bacteria involved throughout the entire manufacturing process from meju to doenjang; some of these bacteria might be present as spores during the doenjang ripening process. Bacillus siamensis was the most populous species of the genus, and Bacillus licheniformis exhibited sufficient salt tolerance to maintain its growth during doenjang ripening. Enterococcus faecalis and Enterococcus faecium, the major lactic acid bacteria (LAB) identified in this study, did not continue to grow under high NaCl conditions in doenjang. Enterococci and certain species of coagulase-negative staphylococci (CNS) were the predominant acid-producing bacteria in meju fermentation, whereas Tetragenococcus halophilus and CNS were the major acid-producing bacteria in doenjang fermentation. We conclude that bacilli, LAB, and CNS may be the major bacterial groups involved in meju fermentation and that these bacterial communities undergo a shift toward salt-tolerant bacilli, CNS, and T. halophilus during the doenjang fermentation process.

• Journal of Microbiology and Biotechnology
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• v.27 no.5
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• pp.995-1004
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• 2017

Culture-dependent methods, such as heterotrophic plate counting (HPC), are usually applied to evaluate the bacteriological quality of hemodialysis water. However, these methods cannot detect the uncultured or viable but non-culturable (VBNC) bacteria, both of which may be quantitatively predominant throughout the hemodialysis water treatment system. Therefore, propidium monoazide (PMA)-qPCR associated with HPC was used together to profile the distribution of the total viable bacteria in such a system. Moreover, high-throughput sequencing of 16S rRNA gene amplicons was utilized to analyze the microbial community structure and diversity. The HPC results indicated that the total bacterial counts conformed to the standards, yet the bacteria amounts were abruptly enhanced after carbon filter treatment. Nevertheless, the bacterial counts detected by PMA-qPCR, with the highest levels of $2.14{\times}10^7copies/100ml$ in softener water, were much higher than the corresponding HPC results, which demonstrated the occurrence of numerous uncultured or VBNC bacteria among the entire system before reverse osmosis (RO). In addition, the microbial community structure was very different and the diversity was enhanced after the carbon filter. Although the diversity was minimized after RO treatment, pathogens such as Escherichia could still be detected in the RO effluent. In general, both the amounts of bacteria and the complexity of microbial community in the hemodialysis water treatment system revealed by molecular approaches were much higher than by traditional method. These results suggested the higher health risk potential for hemodialysis patients from the up-to-standard water. The treatment process could also be optimized, based on the results of this study.

• Journal of Microbiology
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• v.43 no.3
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• pp.219-227
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• 2005

Little is known about the bacterial communities associated with the plants inhabiting sand dune ecosystems. In this study, the bacterial populations associated with two major sand dune plant species, Calystegia soldanella (beach morning glory) and Elymus mollis (wild rye), growing along the costal areas in Tae-An, Chungnam Province, were analyzed using a culture-dependent approach. A total of 212 bacteria were isolated from the root and rhizosphere samples of the two plants, and subjected to further analysis. Based on the analysis of the 16S rDNA sequences, all the bacterial isolates were classified into six major phyla of the domain Bacteria. Significant differences were observed between the two plant species, and also between the rhizospheric and root endophytic communities. The isolates from the rhizosphere of the two plant species were assigned to 27 different established genera, and the root endophytic bacteria were assigned to 21. Members of the phylum Gammaproteobacteria, notably the Pseudomonas species, comprised the majority of both the rhizospheric and endophytic bacteria, followed by members of Bacteroidetes and Firmicutes in the rhizosphere and Alphaproteobacteria and Bacteroidetes in the root. A number of isolates were recognized as potentially novel bacterial taxa. Fifteen out of 27 bacterial genera were commonly found in the rhizosphere of both plants, which was comparable to 3 out of 21 common genera in the root, implying the host specificity for endophytic populations. This study of the diversity of culturable rhizospheric and endophytic bacteria has provided the basis for further investigation aimed at the selection of microbes for the facilitation of plant growth.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.3
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• pp.300-309
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• 2014

Objectives: The objective of this study is to evaluate microbial exposure hazards in the metal-working fluids(MWF) handling industry. Methods: Air quality parameters(airborne bacteria, fungi, endotoxin and oil mist) and bulk MWF in storage tanks were evaluated at 54 points at nine sites in South Korea. Results: The geometric means(GM) of culturable airborne bacteria, fungi, endotoxin and oil mist concentration were $133CFU/m^3$(n=376, range $7{\sim}6,510CFU/m^3$), $159CFU/m^3$(n=381, range $7{\sim}8,469CFU/m^3$), $8.06EU/m^3$(n=103, range $0.34{\sim}280.4EU/m^3$) and $0.20mg/m^3$(n=104, range $0.01{\sim}2.87mg/m^3$), respectively. The ratio of indoor to outdoor concentration was 2.7 for bacteria, 6.1 for endotoxin, and 4.8 for oil mist. Even though average airborne bacteria concentration did not exceed recommended exposure limits($1,000CFU/m^3$), MWF in the storage tanks was highly contaminated with bacteria(arithmetic mean $2.1{\times}10^6CFU/ml$) and exceeded recommended bacteria limits($10^5CFU/ml$). Conclusions: It is necessary for MWF handling workplaces to conduct periodical biohazard inspection of MWF storage tanks. Additionally, further research may be necessary to establish biological occupational exposure limits.