• Korean Journal of Veterinary Research
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• v.62 no.1
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• pp.5.1-5.5
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• 2022

Many countries have imposed regulations relating to concerns that hide contamination will affect the cleanliness of abattoirs. However, South Korea has not indicated any clear criteria. The purpose of this study is to use surrogate bacteria to measure the contamination in abattoirs caused by contaminated cattle hides. The swab contact method and plate count method are used. Surrogate bacteria are found in most internal environments after the final process. These surrogates remained on the carcass even after the final washing process. This paper is the first study in South Korea that use surrogate bacteria to analyze contamination levels in abattoirs.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.345-352
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• 2023

Antibacterial activity against foodborne bacteria (Bacillus cereus, Staphylococcus aureus, Salmonella Enteritidis) and inhibitory activity against murine norovirus, a human norovirus surrogate, of 28 extracts from plants endemic to Korea were investigated in this study. All plant extracts showed antibacterial activity only against gram-positive bacteria, B. cereus and S. aureus. Extracts from Callistemon speciosus and Nymphaea tetragona showed inhibition zones of 16.54 and 24.35 mm against B. cereus and S. aureus, respectively, presenting the highest antibacterial activities recorded in this study. Among all samples, Ardisia japonica extract at concentrations of 100 and 200 ㎍/mL showed the highest virucidal activities of 96.6 and 100.0%, respectively. Ardisia japonica, Duchesnea indica, Polygonum aviculare, and Geum japonicum extracts showed high antibacterial and virucidal activity simultaneously without Raw 264.7 cell cytotoxicity. These plant extracts may serve as potential antimicrobials to control foodborne infections.

• Food Science of Animal Resources
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• v.33 no.4
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• pp.522-530
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• 2013

The ability of probiotics to adhere to the intestinal epithelium likely plays an important role in their colonization of the gastrointestinal tract. Here, we performed high-throughput screening (HTS) for suitable characteristics of potential probiotic bacteria using attachment and colonization ability through a C. elegans surrogate in vivo model. A total of 100 strains of lactic acid bacteria (LAB) isolated from infant feces were subjected to the colonization assay using C. elegans intestine. Based on colonization ability, we showed that nine isolates have a high attachment ability during whole experimental periods (up to 168 h), compared to Lactobacillus rhamnosus strain GG as a control. Also, through the use of an in vitro cell attachment model, nine isolates revealed highly binding activity to the mucus layer. Next, the selected 9 isolates were assayed for their survival ability when exposed to acidic and bile conditions as well as cholesterol reduction and the utilization of prebiotic substrates. As a result, the isolated nine strains were determined to be highly resistant to acid and bile conditions. In addition, they have significant activity for the reduction of cholesterol and utilization of several prebiotic substrates as a carbon source. Finally, the selected nine strains were identified by either L. rhamnosus or L. plantarum (4 strains for L. rhamnosus and 5 strains for L. plantarum, respectively). Taken together, we propose that the direct colonization of probiotics using C. elegans may be applicable to the rapid screening of valuable probiotic strains in vivo.

• Journal of Microbiology and Biotechnology
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• v.25 no.7
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• pp.1015-1025
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• 2015

The development of diverse polymyxin derivatives is needed to solve the toxicity and resistance problems of polymyxins. However, no platform has generated polymyxin derivatives by genetically engineering a polymyxin synthetase, which is a nonribosomal peptide synthetase. In this study, we present a two-step approach for the construction of engineered polymyxin synthetases by substituting the adenylation (A) domains of polymyxin A synthetase, which is encoded by the pmxABCDE gene cluster of Paenibacillus polymyxa E681. First, the seventh L-threonine-specific A-domain region in pmxA was substituted with the L-leucine-specific A-domain region obtained from P. polymyxa ATCC21830 to make polymyxin E synthetase, and then the sixth D-leucine-specific A-domain region (A_6-D-Leu-domain) was substituted with the D-phenylalanine-specific A-domain region (A_6-D-Phe-domain) obtained from P. polymyxa F4 to make polymyxin B synthetase. This step was performed in Escherichia coli on a pmxA-containing fosmid, using the lambda Red recombination system and the sacB gene as a counter-selectable marker. Next, the modified pmxA gene was fused to pmxBCDE on the chromosome of Bacillus subtilis BSK4dA, and the resulting recombinant strains BSK4-PB and BSK4-PE were confirmed to produce polymyxins B and E, respectively. We also succeeded in constructing the B. subtilis BSK4-PP strain, which produces polymyxin P, by singly substituting the A_6-D-Leu-domain with the A_6-D-Phe-domain. This is the first report in which polymyxin derivatives were generated by genetically engineering polymyxin synthetases. The two recombinant B. subtilis strains will be useful for improving the commercial production of polymyxins B and E, and they will facilitate the generation of novel polymyxin derivatives.

• Korean Journal of Microbiology
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• v.55 no.2
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• pp.177-179
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• 2019

Pseudomonas kribbensis CHA-19 was isolated from a temperate forest soil (mid latitude) in New Jersey, USA, for its ability to degrade humic acids, a main component of humic substances (HS), and subsequently confirmed to be able to decolorize lignin (a surrogate for HS) and catabolize lignin-derived ferulic and vanillic acids. The draft genome sequence of CHA-19 was analyzed to discover the putative genes for depolymerization of polymeric HS (e.g., dye-decolorizing peroxidases and laccase-like multicopper oxidases) and catabolic degradation of HS-derived small aromatics (e.g., vanillate O-demethylase and biphenyl 2,3-dioxygenase). The genes for degradative activity were used to propose a HS degradation pathway of soil bacteria.

• Food Science of Animal Resources
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• v.35 no.1
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• pp.91-100
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• 2015

The present study was conducted to screen candidate probiotic strains for anti-inflammatory activity. Initially, a nitric oxide (NO) assay was used to test selected candidate probiotic strains for anti-inflammatory activity in cultures of the murine macrophage cell line, RAW 264.7. Then, the in vitro probiotic properties of the strains, including bile tolerance, acid resistance, and growth in skim milk media, were investigated. We also performed an in vitro hydrophobicity test and an intestinal adhesion assay using Caenorhabditis elegans as a surrogate in vivo model. From our screening, we obtained 4 probiotic candidate lactic acid bacteria (LAB) strains based on their anti-inflammatory activity in lipopolysaccharide (LPS)-stimulated RAW 264.7 cell cultures and the results of the in vitro and in vivo probiotic property assessments. Molecular characterization using 16S rDNA sequencing analysis identified the 4 LAB strains as Lactobacillus plantarum. The selected L. plantarum strains (CAU1054, CAU1055, CAU1064, and CAU1106) were found to possess desirable in vitro and in vivo probiotic properties, and these strains are good candidates for further investigations in animal models and human clinical studies to elucidate the mechanisms underlying their anti-inflammatory activities.

• The Journal of the Korean dental association
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• v.51 no.9
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• pp.501-510
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• 2013

This paper reviews a current view regarding the association between periodontitis and atherosclerotic cardiovascular diseases (ACVD). Many evidences have suggested that there exist biological mechanisms by which periodontitis can lead to ACVD. Periodontal infection can lead to direct bacterial invasion into endothelial tissues through the blood stream, then the bacteria can activate the host inflammatory response followed by atheroma formation, maturation and exacerbation. Also, chronic periodontal infections may indirectly induce endothelial activation or dysfunction through a state of systemic inflammation as evidenced by elevated plasma acute proteins, IL-6 and fibrinogen as well. There is moderate evidence that periodontal treatment can reduce systemic inflammation and improvement of both clinical surrogate markers. But there is no periodontal intervention study available on primary ACVD prevention. There is consistent and strong epidemiologic evidence, including in vitro, animal and clinical studies, that periodontitis imparts increased risk for future ACVD. However, evidences from intervention trials to date are not sufficient to confirm the multi directional causality of periodontitis in ACVD etiology. Well-designed intervention trials on the impact of periodontal treatment on the prevention of ACVD outcomes are needed.

• Journal of Korean Society on Water Environment
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• v.21 no.5
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• pp.470-476
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• 2005

The Korean Water Quality Index (K-WQI) was applied to the rivers located in the watershed of Daecheong Lake to assess the status of river water quality, and propose potential target constituents for better water quality management in the watershed. The estimated K-WQI value for each river was varied from 70 to 90, and Youngdongcheon showed the worst score while Mujunamdeachen showed the best score. The total nitrogen (TN) and total coliform bacteria were identified as the most significant constituents that degrade the K-WQI values in the rivers. The correlation coefficients (r) were determined between K-WQI and the delivered specific load ($kg/km^2/yr$) of BOD, TN, and TP to justify potential target constituents that have a great influence on the improvement of K-WQI values. The results showed that TN (r=-0.86) and TP (r=-0.85) have a strong negative relationships with K-WQI, but BOD have almost no effect. This implies that BOD, the surrogate parameter for organic pollutants, is no more a feasible water quality variable for the water quality management in the study site.

• Journal of Soil and Groundwater Environment
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• v.19 no.2
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• pp.16-24
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• 2014

To test the potential effects of extracellular electron shuttles (EES) on the rate and extent of heavy metal release from contaminated soils during microbial iron reduction, we created anaerobic batch systems with anthraquinone-2,6-disulfonate (AQDS) as a surrogate of EES, and with contaminated soils as mixed iron (hydr)oxides and microbial sources. Two types of soils were tested: Zn-contaminated soil A and As/Pb-contaminated soil B. In soil A, the rate of iron reduction was fastest in the presence of AQDS and > 3500 mg/L of total Fe(II) was produced within 2 d. This suggests that indigenous microorganisms can utilize AQDS as EES to stimulate iron reduction. In the incubations with soil B, the rate and extent of iron reduction did not increase in the presence of AQDS likely because of the low pH (< 5.5). In addition, less than 2000 mg/L of total Fe(II) was produced in soil B within 52 d suggesting that iron reduction by subsurface microorganisms in soil B was not as effective as that in soil A. Relatively high amount of As (~500 mg/L) was released to the aqueous phase during microbial iron reduction in soil B. The release of As might be due to the reduction of As-associated iron (hydr)oxides and/or direct enzymatic reduction of As(V) to As(III) by As-reducing microorganisms. However, given that Pb in liquid phase was < 0.3 mg/L for the entire experiment, the microbial reduction As(V) to As(III) by As-reducing microorganisms has most likely occurred in this system. This study suggests that heavy metal release from contaminated soils can be strongly controlled by subsurface microorganisms, soil pH, presence of EES, and/or nature of heavy metals.

• Journal of Environmental Health Sciences
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• v.48 no.2
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• pp.116-122
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• 2022

Background: The recent COVID-19 pandemic is one of the worst disease outbreaks of the 21th century. Due to a lack of reliable antiviral therapeutics, wearing face masks is recommended to prevent airborne infection originating from virus-contaminated bioaerosols. Objectives: The aim of this study was to evaluate the filtration efficiencies of face masks that are commercially available in South Korea for a biological aerosol of Staphylococcus aureus (S. aureus) and murine coronavirus, a well-known surrogate for human coronaviruses. Methods: We collected six different kinds of commercial masks: two Korea Filter (KF)94 (KF94-1, KF94-2) masks, one surgical (Surgical-1) mask, one anti-droplet (KF-AD-1) mask, and two dust (Dust-1, Dust-2) face masks. S. aureus (ATCC 6538), a well-performing test bacteria and murine coronavirus (ATCC VR-764) were prepared under a suitable culture condition. Then, a mask biological filtration tester was used to examine the microbial filtration efficiencies of masks. Test microorganisms were quantitatively measured via cultivation methods and microbial filtration efficiencies were calculated appropriately. Results: All face masks showed over 99.6% filtration efficiency for S. aureus or murine coronavirus. There were no significant differences among the bacterial filtration efficiencies of the face masks. KF94-1 (99.97±0.08%) and Dust-1 mask (99.97±0.07%) showed the highest (over 99.9%) filtration efficiency for murine coronavirus. KF94-1 or Dust-1 masks showed a significant virus filtration efficiency compared to Surgical-1 mask (p<0.05; Mann-Whitney U test). Conclusions: All the commercially available face masks used in this study can filter S. aureus or murine coronavirus in bioaerosols efficiently, regardless of the mask type. Therefore, our results suggest that wearing a certified face mask is a reliable means to prevent the transmission of infectious airborne diseases via biological aerosols.