• Microbiology and Biotechnology Letters
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• v.47 no.1
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• pp.125-131
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• 2019

We have isolated and identified 72 bacterial strains from four bentonite samples collected at the mining areas located in Gyeongsangbuk-do, Republic of Korea, and measured their hydrolytic enzyme (${\alpha}$-amylase, protease, and cellulase) activities to identify the isolates with industrial-use potential. Most of the isolates belonged to the Bacillaceae, with minor portions being from the Paenibacillaceae, Micrococcaceae, and Bacillales Family XII at the family level. Of the strains isolated, 33 had extracellular ${\alpha}$-amylase activity, 30 strains produced cellulase, and 35 strains produced protease. Strain MBLB1268, having the highest ${\alpha}$-amylase activity, was identified as Bacillus siamensis ($0.38{\pm}0.06U/ml$). Bacillus tequilensis MBLB1223, isolated from Byi33-b, showed the highest cellulase activity ($0.26{\pm} 0.04U/ml$), whereas Bacillus wiedmannii MBLB1197, isolated from Zdb130-b, exhibited the highest protease activity ($54.99{\pm}0.78U/ml$). These findings show that diverse bacteria of the Bacillaceae family adhere to and exist in bentonite and are potential sources of industrially useful hydrolytic enzymes.

• The Plant Pathology Journal
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• v.37 no.6
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• pp.652-661
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• 2021

Xanthomonas citri pv. glycines (Xcg) is a major pathogen of soybean (Glycine max) in South Korea, despite the availability of soybean varieties with some resistance. We conducted a nationwide survey of the incidence and severity of bacterial pustule caused by Xcg. The percentage of infected fields was 7% to 17% between 2015 and 2017. We characterized the diversity of a nationwide collection of 106 Xcg isolates based on avrBs3 banding patterns. The isolates fell into 11 groups, each represented by a type strain; only two of these were similar to isolates collected from 1999 to 2002. The diversity of Xcg strains increased and the dominant strains changed between 1999 and 2017, with three new type strains comprising 44% of the isolates examined in 2012 to 2017. Pathogenicity tests did not show evidence for a shift in the races or aggressiveness of Xcg strains. Korean soybean cultivars, including the widely-grown Daewon cultivar, were susceptible to the 11 new type strains. The cultivar CNS, which carries the rxp resistance gene, was susceptible to most type strains, including two representing 83% of the Korean Xcg strains. In contrast, Williams 82, which also carries rxp, showed resistance to at least five type strains. Collectively, these results suggest that Williams 82 has resistance loci in addition to rxp. The widespread distribution of Xcg, the high virulence of the current endemic strains, and the low resistance of most Korean soybean cultivars collectively favor widespread disease in Korea in years that are favorable to pustule development.

• Korean Journal of Microbiology
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• v.53 no.4
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• pp.242-250
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• 2017

Actinobacteria tolerating extreme conditions can be a rich source of bioactive compounds and enzymes. In this study filamentous actinobacteria were isolated from soils of Ulleung Island, and their physiological properties were examined. Soil samples were collected, serially diluted and spread on various agar media. The average viable counts of total bacteria were $1.28{\times}10^7CFU/g$ for soil sample 1 (ULS1) and $2.05{\times}10^7CFU/g$ for soil sample 2 (ULS2). As a result, 34 strains of actinobacteria were isolated and assigned to the genera Streptomyces (16 strains), Isoptericola (5 strains), Rhodococcus (4 strains), Agromyces (3 strains), Micrococcus (2 strains), Arthrobacter (1 strain), Williamsia (1 strain), Microbacterium (1 strain), and Oerskovia (1 strain) based on 16S rRNA gene sequence analysis. Enzyme activity and plant growth promoting potential were tested for representative isolates. Multiple strains of Streptomyces degraded starch, casein and Tween 80. As for plant growth promoting potential, strains of Oerskovia, Williamsia, Isoptericola, and Streptomyces solubilized phosphate, and those of Agromyces, Oerskovia, Micrococcus, Rhodococcus, Streptomyces, and Isoptericola produced 3-indole-acetic acid (IAA), respectively. Selected strains of Streptomyces exhibited strong antagonistic activity against Staphylococcus aureus and Bacillus subtilis as well as Candida albicans. This study confirms that actinobacteria from Ulleung Island can be a good source of novel bioactive compounds.

• Journal of Species Research
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• v.5 no.1
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• pp.188-200
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• 2016

During recent screening to discover indigenous prokaryotic species in South Korea, a total of 31 bacterial strains assigned to the class Gammaproteobacteria were isolated from a variety of environmental samples including soil, tidal flat, freshwater, seawater, and plant roots. From the high 16S rRNA gene sequence similarity (>98.7%) and formation of a robust phylogenetic clade with the closest species, it was determined that each strain belonged to each independent and predefined bacterial species. There is no official report that these 31 species have been described in South Korea; therefore 5 species of 3 genera in the order Alteromonadales, 11 species of 3 genera in the order Pseudomonadales, 8 species of 6 genera in the order Enterobacteriales, 2 species of 1 genera in the order Vibrionales, 1 species of 1 genera in the order Oceanospirillales, 3 species of 3 genera in the order Xanthomonadales, and 1 species in the order Spongiibacter_o within the Gammaproteobacteia are reported for proteobacterial species found in South Korea. Gram reaction, colony and cell morphology, basic biochemical characteristics, isolation source, and strain IDs are also described in the species description section.

• Journal of Species Research
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• v.5 no.1
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• pp.166-178
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• 2016

An outcome of the study to discover indigenous prokaryotic species in Korea, a total of 26 bacterial species assigned to the classes Bacteroidetes and Firmicutes were isolated from diverse environmental samples collected from soil, tidal flat, freshwater, seawater, wetland, plant roots, and fermented foods. From the high 16S rRNA gene sequence similarity (>99.0%) and formation of a robust phylogenetic clade with the closest species, it was determined that each strain belonged to each independent and predefined bacterial species. There is no official report that these 26 species have been described in Korea; therefore 14 strains for the order Flavobacteriales and two strains for the order Cytophagales were assigned to the class Bacteroidetes, and 8 strains for the order Bacillales and 4 strains for the order Lactobacillales were assigned to the class Firmicutes are reported for new bacterial species found in Korea. Gram reaction, colony and cell morphology, basic biochemical characteristics, isolation source, and strain IDs are also described in the species description section.

• Journal of Microbiology and Biotechnology
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• v.27 no.1
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• pp.101-111
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• 2017

The task of improving a fungal strain is highly time-consuming due to the requirement of a large number of flasks in order to obtain a library with enough diversity. In addition, fermentations (particularly those for fungal cells) are typically performed in high-volume (100-250 ml) shake-flasks. In this study, for large and rapid screening of itaconic acid (IA) high-yielding mutants of Aspergillus terreus, a miniaturized culture method was developed using 12-well and 24-well microtiter plates (MTPs, working volume = 1-2 ml). These miniaturized MTP fermentations were successful, only when highly filamentous forms were induced in the growth cultures. Under these conditions, loose-pelleted morphologies of optimum sizes (less than 0.5 mm in diameter) were casually induced in the MTP production cultures, which turned out to be the prerequisite for the active IA biosynthesis by the mutated strains in the miniaturized fermentations. Another crucial factor for successful MTP fermentation was to supply an optimal amount of dissolved oxygen into the fermentation broth through increasing the agitation speed (240 rpm) and reducing the working volume (1 ml) of each 24-well microtiter plate. Notably, almost identical fermentation physiologies resulted in the 250 ml shake-flasks, as well as in the 12-well and 24-well MTP cultures conducted under the respective optimum conditions, as expressed in terms of the distribution of IA productivity of each mutant. These results reveal that MTP cultures could be considered as viable alternatives for the labor-intensive shake-flask fermentations even for filamentous fungal cells, leading to the rapid development of IA high-yield mutant strains.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.498-508
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• 2019

Bacillus species were isolated from iru, a traditional fermented condiment in Nigeria. Polyphasic approach was used to evaluate the phylogenetic relationship and strain sub-type of the isolated species. Additionally, the phylogenetic profiles of the species isolated from iru were compared with those of bacilli isolated from different continents. The phylogenetic diversity analysis was performed using the combination of 16S rRNA gene sequencing, ITS-PCR, ITS-PCR-RFLP, and M13 RAPD-PCR. The analysis revealed that Bacillus subtilis U170B and B. subtilis U146A isolated from iru were the closest relatives of strains belonging to the phylogeny of B. subtilis sensu stricto and were related to other bacilli isolated from different continents that had functional benefits. The two isolated species exhibited resistance to acidic pH (pH 2.0). The survival rates of B. subtilis U170B, B. subtilis U146A, and B. clausii UBBC-07 (commercial probiotic strain) cultured at pH 2.0 for 3 h were 33.45, 12.44, and 9.53%, respectively. The strains were highly tolerant to bile salts [0.3% (w/v)]. B. subtilis U170B exhibited the highest cell viability (43.45%) when cultured for 3 h in the presence of bile salts, followed by B. subtilis U146A (25%) and B. clausii UBBC-07 (18.94%). B. subtilis U170B and B. subtilis U146A did not exhibit haemolytic activity and were susceptible to different antibiotics. Additionally, these two strains exhibited weak antagonistic activity against B. cereus. The diverse wild strains of B. subtilis can be used as a safe multifunctional starter culture for the industrial production of condiments with health benefits.

• Journal of Species Research
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• v.6 no.2
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• pp.141-153
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• 2017

During an investigation of the biodiversity of bacterial species in Korea, we discovered many indigenous prokaryotic species. A total of 39 bacterial strains in the class Alphaproteobacteria were isolated from various environmental samples collected from marine organisms, sea water, fresh water, tap water, mud flats, activated sludge, mineral water, tidal flats, soil and decayed plants. From the high 16S rRNA gene sequence similarity (>98.7%) and formation of robust phylogenetic clades with the most closely related species, it was determined that each strain belonged to each independent and predefined bacterial species. There is no official report that any of these 39 Alphaproteobacteria species have been described in Korea. Specifically, 18 species in 11 genera in the order Sphingomonadales, 11 species in 10 genera in the order Rhizobiales, two species in two genera in the order Caulobacterales, six species in six genera in the order Rhodobacterales and two species in two genera in the order Rhodospirillales were found in Korea. Gram reaction, colony and cell morphology, basic biochemical characteristics, isolation source, and strain IDs are described in the species description section.

• Journal of Species Research
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• v.6 no.2
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• pp.119-128
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• 2017

Within a comprehensive, widescale investigation of indigenous prokaryotic species in Korea, 29 bacterial strains in the phylum Bacteroidetes were isolated from diverse environmental habitats that included soil, plant roots, natural caves, tidal flats, freshwater from lakes, and seawater. Based on their high 16S rRNA gene sequence similarities (>99.1%) and the formation of robust phylogenetic clades with the closest type species, each strain likely belonged to an independent and predefined bacterial species. There are no publications or official reports of the isolation of these 29 species in Korea. Our study provides strong evidence that seven species in three genera in the order Cytophagales, 15 species in 13 genera in the order Flavobacteriales and seven species in five genera in the order Sphingobacteriales, all within the phylum Bacteriodetes, are new reports of bacterial species in Korea. Gram reaction, colony and cell morphology, basic biochemical characteristics, isolation source, and strain IDs are described in the species description section.

• Journal of Species Research
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• v.6 no.2
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• pp.129-140
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• 2017

During a comprehensive investigation of indigenous prokaryotic species in Korea, a total 31 bacterial strains assigned to the class Alphaproteobacteria were isolated from diverse environmental habitats including freshwater, seawater, brackish water, ginseng soil, plant roots, natural caves, and tidal flats. Based on their high 16S rRNA gene sequence similarities(>99.1%) and formation of robust phylogenetic clades with the closest type species, each strain was assigned to an independent and predefined bacterial species. Because there were no published or official reports regarding the isolation of these 31 species in Korea, this study identified three species in two genera in the order Caulobacterales, 12 species in 10 genera in the order Rhodobacterales, three species in two genera in the order Rhizobiales, two species in two genera in the order Rhodospirillales and 11 species in seven genera, all in the order Sphingomonadaceae within the Alphaproteobacteria are reported as new alphaproteobacterial species in Korea. Gram reaction, colony and cell morphology, basic biochemical characteristics, isolation source, and strain IDs are described in the species description section.