• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.4
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• pp.507-515
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• 2024

Microbial forensics is a scientific discipline for analyzing evidence related to biological crimes by identifying the origin of microorganisms. Multiple locus variable number tandem repeat analysis(MLVA) is one of the microbiological analysis methods used to specify subtypes within a species based on the number of tandem repeat in the genome, and advances in next generation sequencing(NGS) technology have enabled in silico anlysis of full-length whole genome sequences. In this paper, we analyzed unknown samples provided by Robert Koch Institute(RKI) through The United Nations Secretary-General's Mechanism(UNSGM)'s external quality assessment exercise(EQAE) project, which we officially participated in 2023. We confirmed that the 3 unknown samples were B. anthracis through nucleic acid isolation and genetic sequence analysis studies. MLVA results on 32 loci of B. anthracis were analysed by using genome sequences obtained from NGS(NextSeq and MinION) and Sanger sequencing. The MLVA typing using short-reads based NGS platform(NextSeq) showed a high probability of causing assembly error when a size of the tandem repeats was grater than 200 bp, while long-reads based NGS platform(MinION) showed higher accuracy than NextSeq, although insertion and deletion was observed. We also showed hybrid assembly can correct most indel error caused by MinION. Based on the MLVA results, genetic identification was performed compared to the 2,975 published MLVA databases of B. anthracis, and MLVA results of 10 strains were identical with 3 unkonwn samples. As a result of whole genome alignment of the 10 strains and 3 unknown samples, all samples were identified as B. anthracis strain A4564 which is associated with injectional anthrax isolates in heroin users.

• Journal of Environmental Health Sciences
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• v.50 no.2
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• pp.93-101
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• 2024

Background: As pollutants caused by non-point sources flow into rivers, river water quality monitoring for fecal pollution is becoming increasingly important. Objectives: This study was conducted to investigate the distribution of microbial communities in the Yeongsangang River water system and sewage treatment plants in Gwangju and to evaluate their antibiotic resistance. Methods: In the experiment, samples were distributed to five selective media at each point and then cultured for 18 to 24 hours. When bacteria were observed, they were sub-cultured by size and shape and identified using MALDI-TOF MS equipment. When identification was completed, 17 types of antibiotic susceptibility tests were performed using VITEK II equipment, focusing on gram-negative dominant species among the identified strains. Results: During the study period, a total of 266 strains were isolated from 39 samples. Gram-positive bacteria were 37 strains in four genera, or 13.9% of the total, and Gram-negative bacteria were 229 strains in 23 genera, or 86.1% of the total. Antibiotic susceptibility testing of 23 strains, the major dominant species, showed that one strain (4.3%) was resistant to only one antibiotic, and two strains (8.7%) were 100% susceptible to the 17 antibiotics tested. The other 20 strains (87.0%) were multidrug resistant bacteria resistant to two or more antibiotics. There were various types of multidrug resistance. Among them, penicillin and cephalosporin series showed the highest resistance. Conclusions: Based on the results of this study, it was found that the bacterial community structure changed according to regional and environmental factors, and it was judged that continuous research such as genetic analysis of antibiotic-resistant bacteria present in natural rivers is necessary.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.394-403
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• 2023

In the pursuit of sustainable and environmentally-friendly agricultural practices, we conducted an extensive study on the rhizosphere bacteria inhabiting soils that have been devoid of chemical fertilizers for an extended period exceeding 40 years. Through this investigation, we isolated a total of 80 species of plant growth-promoting rhizosphere bacteria and assessed their potential to enhance plant growth. Among these isolates, Burkholderia cepacia CD2 displayed remarkable plant growth-promoting activity, making it an optimal candidate for further analysis. Burkholderia cepacia CD2 exhibited a range of beneficial characteristics conducive to plant growth, including phosphate solubilization, siderophore production, denitrification, nitrate utilization, and urease activity. These attributes are well-known to positively influence the growth and development of plants. To validate the taxonomic classification of the strain, 16S rRNA gene sequencing confirmed its placement within the Burkholderia genus, providing further insights into its phylogenetic relationship. To delve deeper into the potential mechanisms underlying its plant growth-promoting properties, we sought to confirm the presence of specific genes associated with plant growth promotion in CD2. To achieve this, whole genome sequencing (WGS) was performed by Plasmidsaurus Inc. (USA) utilizing Oxford Nanopore technology (Abingdon, UK). The WGS analysis of the genome of CD2 revealed the existence of a subsystem function, which is thought to be a pivotal factor contributing to improved plant growth. Based on these findings, it can be concluded that Burkholderia cepacia CD2 has the potential to serve as a microbial fertilizer, offering a sustainable alternative to chemical fertilizers.

• Journal of Microbiology and Biotechnology
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• v.25 no.5
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• pp.662-671
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• 2015

To enrich the genetic resource of microbial xylanases with high activity and stability under alkaline conditions, a xylanase gene (xynSL4) was cloned from Planococcus sp. SL4, an alkaline xylanase-producing strain isolated from the sediment of soda lake Dabusu. Deduced XynSL4 consists of a putative signal peptide of 29 residues and a catalytic domain (30-380 residues) of glycosyl hydrolase family 10, and shares the highest identity of 77% with a hypothetical protein from Planomicrobium glaciei CHR43. Phylogenetic analysis indicated that deduced XynSL4 is closely related with thermophilic and alkaline xylanases from Geobacillus and Bacillus species. The gene xynSL4 was expressed heterologously in Escherichia coli and the recombinant enzyme showed some superior properties. Purified recombinant XynSL4 (rXynSL4) was highly active and stable over the neutral and alkaline pH range from 6 to 11, with maximum activity at pH 7 and more than 60% activity at pH 11. It had an apparent temperature optimum of 70℃ and retained stable at this temperature in the presence of substrate. rXynSL4 was highly halotolerant, retaining more than 55% activity with 0.25-3.0 M NaCl and was stable at the concentration of NaCl up to 4M. The enzyme activity was significantly enhanced by β-mercaptoethanol and Ca²⁺ but strongly inhibited by heavy-metal ions and SDS. This thermophilic and alkaline- and salt-tolerant enzyme has great potential for basic research and industrial applications.

• Microbiology and Biotechnology Letters
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• v.26 no.4
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• pp.358-364
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• 1998

New microbial-control agents were prepared with B. thuringiensis strain NT0423 having unique properties which are different with other B. thuringiensis strains belonging to serotype 7[Kor. J. Appl. Entomol. 32: 426-432.]. Three B. thuringiensis formulations designated as BioBact 10%, 20% and 40%, were made with various combinations of adjuvants. These formulations showed good physical properties in wettability, suspensibility, particle size and adherence. In addition the result of SDS-PAGE analysis indicated that $\delta$-endotoxins remain stably in all formulations. Among the tested formulations, two wettable powder formulations, BioBact 20% and 40%, comprising 20% and 40% of B. thuringiensis technical powder showed the effective control against diamondback moth larvae (Plutella xylostella) in laboratory and field tests. Especially, when compared with commercial B. thuringiensis formulations (A and B commercial formulations) in field evaluation, BioBact 20% and 40% formulations showed equal activity up to 80% lethality and a good persistence effect which remain on leaves at least 7 days.

• The Korean Journal of Mycology
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• v.30 no.2
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• pp.147-151
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• 2002

Trichoderma spp. are the aggressive causal agents for green mold disease on oyster mushroom (Pleurotus spp.) cultivation. Antifungal bacteria (KATB 99121, KATB 99122 and KATB 99123 strains) were isolated from the compost for Pleurotus ostreatus. Among these bacterial strains, KATB 99121 strain showed an excellent inhibitory activity to the pathogens for green molds such as T. harzianum, T. viride and T. hamatum and an animal pathogen, Candida albicans, but did not affect on the culture of Pleurotus ostreatus (2209, Chunchu 2 and Wonhyung strains). KATB 99121 strain secreted amylolytic, proteolytic and cellulolytic exoenzymes. KATB 99122 and KATB 99123 strains excreted amylolytic, proteolytic, cellulolytic, lipolytic exoenzymes and showed ${\beta}$-glucosidase activity. Further studies will be conducted on the development of microbial fungicides using the antagonistic bacteria for the control of green mold disease on Pleurotus spp.

• Journal of Microbiology and Biotechnology
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• v.8 no.6
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• pp.606-612
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• 1998

A microbial flocculant-producing gram-positive bacterium, strain TE11, was isolated from soil samples, and was identified as Bacillus subtilis by using the Midi system, the Biolog system, 16S rDNA sequence analysis, and some physiological and morphological characteristics. The maximum flocculant capsular biopolymer of TE11 strain (BCP, 4.9mg/ml) was obtained when it was grown in GA broth medium containing 3% glutamic acid, 2% glycerol, 0.5% citric acid, 0.5% $NH_4$Cl, 0.05% $MgSO_4.7H_2O,\; 0.05%\;K_2HPO_4\;,\; and\; 0.004%\; FeC1_3. 6H_2O,\; pH 7.2,\; at\; 30^{\circ}C$ for 70 h with shaking. When glycerol was used as an additional carbon source in the GA medium, TE11 produced only flocculant BCP without any by-product. The flocculant (BCP) was found to aggregate suspended kaolin and activated charcoal powder without cations, and its flocculating activity was significantly enhanced by the addition of bivalent cations such as $Ca^{2＋}.Zn^{2},\; and\; Mn^{2＋}$. The flocculation activity by addition of $Ca^{2+}$ was high in an acidic pH 4.0. In the case of $Zn^{2＋}$, high flocculating activity remained without significant loss in the broad range of pH 4.0 to 9.0.

• Applied Biological Chemistry
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• v.38 no.1
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• pp.13-19
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• 1995

In order to produce phenylalanine without tyrosine co-production, we constructed various temperature-controllable expression vectors by insertion of lower expression of the tyrA gene into the plasmid pSY130-14. And tyrosine revertant to cultivate without addition of tyrosine, was selected from Escherichia coli strain AT2471[tyrA , thi ] by spontaneous mutation. The strain AT2471 harbouring plasmid pSY146A and the tyrosine revertant 5 harbouring plasmid pSY111-14 produced 12 g/l and 15 g/l of phenylalanine respectively in a 2.5 l jar fermenter at a constant temperature of $39^{\circ}C$ after 55 hours cultivation.

• Journal of the Korea Organic Resources Recycling Association
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• v.15 no.4
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• pp.125-130
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• 2007

Six bacteria, which showed the flocculating activity to food wastewater, were isolated from various environment. These strains were identified as Bacillus pumilus, Enterobacter sp., Pantotea agglomerans, Bacillus licheniformis, and two Bacillus sps. Among them, the flocculating activities of three strains, such as Enterobacter sp.(YK102), Bacillus sp.(YK103), and Pantotea agglomerans (YK104), were eight times or more higher than that of the control strain, Zoogloea ramigera. in the test with 0.5% kaolin. In the experiment with food wastewater, Enterobacter sp.(YK102) showed the highest flocculating activity which was 2.5 times higher than that of a control strain, Pseudomonas fluorescens.

• Journal of Microbiology and Biotechnology
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• v.20 no.11
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• pp.1534-1538
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• 2010

Fed-batch cultures of Hansenula polymorpha were studied to develop an efficient biosystem to produce recombinant human serum albumin (HSA). To comply with this purpose, we used a high-purity oxygen-supplying strategy to increase the viable cell density in a bioreactor and enhance the production of target protein. A mutant strain, H. polymorpha GOT7, was utilized in this study as a host strain in both 5-l and 30-l scale fermentors. To supply high-purity oxygen into a bioreactor, nearly 100% high-purity oxygen from a commercial bomb or higher than 93% oxygen available in situ from a pressure swing adsorption (PSA) oxygen generator was employed. Under the optimal fermentation of H. polymorpha with highpurity oxygen, the final cell densities and produced HSA concentrations were 24.6 g/l and 5.1 g/l in the 5-l fermentor, and 24.8 g/l and 4.5 g/l in the 30-l fermentor, respectively. These were about 2-10 times higher than those obtained in air-based fed-batch fermentations. The discrepancies between the 5-l and 30-l fermentors with air supply were presumably due to the higher contribution of surface aeration over submerged aeration in the 5-l fermentor. This study, therefore, proved the positive effect of high-purity oxygen in enhancing viable cell density as well as target recombinant protein production in microbial fermentations.