• Journal of Microbiology and Biotechnology
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• 제15권5호
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• pp.1039-1046
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• 2005

The salt resistance of antibacterial activity and synergistic effect with clinically used antibiotic agents are critical factors in developing effective peptide antibiotic drugs. For this reason, we investigated the resistance of antibacterial activity to antagonism induced by NaCl and $MgCl_2$ and the synergistic effect of P20 with cefotaxime. P20 is a 20-residue synthetic peptide derived from a cecropin A (CA)-melittin(ME) hybrid peptide. In this study, P20 was found to have potent antibacterial activity against clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) strains without hemolytic activity against human erythrocytes. The combination study revealed that P20 in combination with cefotaxime showed synergistic antibacterial activity in an energy-dependent manner. We also confirmed the synergism between P20 and cefotaxime by fluorescence-activated flow cytometric analysis by staining bacterial cells with propidium iodide (PI) and bis-(1,3-dibutylbarbituric acid) trimethine oxonol (BOX). This study suggests that P20 may be useful as a therapeutic antibiotic peptide with synergistic effect in combination with conventional antibiotic agents.

• BMB Reports
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• 제42권5호
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• pp.281-285
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• 2009

Peroxisomes play an important role in cellular defense systems and generate secondary messengers for cellular communication. Saccharomyces cerevisiae containing oleate-induced peroxisomes were subjected to buffer-soluble extraction and two chromatographic procedures, and a protein with antifungal activity was isolated. The results of MALDI-TOF analysis identified the isolated protein as peroxisomal 3-ketoacyl-CoA thiolase (ScFox3). Purified yeast ScFox3 exhibited thiolase activity that catalyzed the thiolytic cleavage of 3-ketoacyl-CoA to acetyl-CoA and acyl-CoA. ScFox3 protein inhibited various pathogenic fungal strains, with the exception of Aspergillus flavus. Using ScFox3-GFP and PTS2 signal-truncated ScFox3M-GFP, we showed that only ScFox3-GFP, with an intact PTS2 peroxisome signal sequence, was able to translocate into peroxisomes. Yeast ScFox3 is a natural antifungal agent found in peroxisomes.

• Journal of Microbiology and Biotechnology
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• 제16권6호
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• pp.880-888
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• 2006

Pleurocidin, an $\alpha$-helical cationic antimicrobial peptide, was isolated from skin mucosa of winter flounder (Pleuronectes americamus). It had strong antimicrobial activities against Gram-positive and Gram-negative bacteria, but had very weak hemolytic activity. The Gly$^{13,17}\rightarrow$Ala analog (pleurocidin-AA) showed similar antibacterial activities, but had dramatically increased hemolytic activity. The bacterial cell selectivity of pleurocidin was confirmed through the membrane-disrupting and membrane-binding affinities using dye leakage, tryptophan fluorescence blue shift, and tryptophan quenching experiments. However, the non-cell-selective antimicrobial peptide, pleurocidin-AA, interacts strongly with both negatively charged and zwitterionic phospholipid membranes, the latter of which are the major constituents of the outer leaflet of erythrocytes. Circular dihroism spectra showed that pleurocidin-AA has much higher contents of $\alpha$-helical conformation than pleurocidin. The tertiary structure determined by NMR spectroscopy showed that pleurocidin has a flexible. structure between the long helix from $Gly^3$ to $Gly^{17}$ and the short helix from $Gly^{17}$ to $Leu^{25}$. Cell-selective antimicrobial peptide pleurocidin interacts strongly with negatively charged phospholipid membranes, which mimic bacterial membranes. Structural flexibility between the two helices may play a key role in bacterial cell selectivity of pleurocidin.

• Journal of Microbiology and Biotechnology
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• 제27권4호
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• pp.685-693
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• 2017

Candidiasis involving the biofilms of Candida albicans is a threat to immunocompromised patients. Candida biofilms are intrinsically resistant to the antifungal drugs and hence novel treatment strategies are desired. The study intended to evaluate the anti-Candida activity of allyl isothiocyanate (AITC) alone and with fluconazole (FLC), particularly against the biofilms. Results revealed the concentration-dependent activity of AITC against the planktonic growth and virulence factors of C. albicans. Significant (p <0.05) inhibition of the biofilms was evident at ${\leq}1mg/ml$ concentrations of AITC. Notably, a combination of 0.004 mg/ml of FLC and 0.125 mg/ml of AITC prevented the biofilm formation. Similarly, the preformed biofilms were significantly (p <0.05) inhibited by the AITC-FLC combination. The fractional inhibitory concentration indices ranging from 0.132 to 0.312 indicated the synergistic activity of AITC and FLC against the biofilm formation and the preformed biofilms. No hemolytic activity at the biofilm inhibitory concentrations of AITC and the AITC-FLC combination suggested the absence of cytotoxic effects. The recognizable synergy between AITC and FLC offers a potential therapeutic strategy against biofilm-associated Candida infections.

• Journal of Microbiology and Biotechnology
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• 제28권8호
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• pp.1299-1309
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• 2018

We previously reported on lactophoricin (LPcin), a cationic ${\alpha}-helical$ antimicrobial peptide derived from bovine milk, which has antimicrobial effects on Candida albicans as well as Gram-positive and Gram-negative bacteria. In this study, we designed the LPcin-YK3 peptide, a shorter analog of LPcin, and investigated its antimicrobial activity. This peptide, consisting of 15 amino acids with + 3 net charges, was an effective antimicrobial agent against the on the Gram-positive strain, Staphylococcus aureus (MIC: $0.62{\mu}g/ml$). In addition, the hemolytic activity assay revealed that the peptide was not toxic to mouse and human erythrocytes up to $40{\mu}g/ml$. We also used circular dichroism spectroscopy to confirm that peptide in the presence of lipid has ${\alpha}-helical$ structures and later provide an overview of the relationship between each structure and antimicrobial activity. This peptide is a member of a new class of antimicrobial agents that could potentially overcome the problem of bacterial resistance caused by overuse of conventional antibiotics. Therefore, it could be used as a therapeutic or natural additive, particularly in the cosmetics industry.

• 한국미생물·생명공학회지
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• 제51권2호
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• pp.167-173
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• 2023

Proteolytic enzymes secreted by Aspergillus, as pathogenicity factors, affect blood coagulation and fibrinolysis, and therefore the target proteins of their action in the bloodstream are of significant interest. In the present study, the action of the isolated protease of A. terreus 2 on different human plasma proteins was shown. The protease of A. terreus 2 exhibited the highest proteolytic activity against hemoglobin, which was 2.5 times higher than the albuminolytic activity shown in both of the protein substrates used. In addition, the protease has significant ability to hydrolyze both fibrin and fibrinogen. However, the inability of the A. terreus 2 protease to coagulate rabbit blood plasma and coagulate human and bovine fibrinogen indicates the severity of the enzyme's action on human blood coagulation factors. It should be considered as a potential indicator of this isolated protease's participation in fungal pathogenesis. The protease shows no hemolytic activity. Furthermore, its activity is insignificantly inhibited by thrombin inhibitors, and is not inhibited by plasmin inhibitors.

• Journal of Microbiology and Biotechnology
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• 제33권12호
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• pp.1625-1634
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• 2023

Leuconostoc lactis strain DMLL10 was isolated from kimchi, a fermented vegetable, as a starter candidate through safety and technological assessments. Strain DMLL10 was susceptible to ampicillin, chloramphenicol, clindamycin, erythromycin, gentamicin, kanamycin, streptomycin, and tetracycline. It did not show any hemolytic activity. Regarding its phenotypic results related to its safety properties, genomic analysis revealed that strain DMLL10 did not encode for any toxin genes such as hemolysin found in the same genus. It did not acquire antibiotic resistance genes either. Strain DMLL10 showed protease activity on agar containing NaCl up to 3%. The genome of DMLL10 encoded for protease genes and possessed genes associated with hetero- and homo-lactic fermentative pathways for lactate production. Finally, strain DMLL10 showed antibacterial activity against seven common foodborne pathogens, although bacteriocin genes were not identified from its genome. These results indicates that strain DMLL10 is a novel starter candidate with safety, enzyme activity, and bacteriocin activity. The complete genomic sequence of DMLL10 will contribute to our understanding of the genetic basis of probiotic properties and allow for assessment of the effectiveness of this strain as a starter or probiotic for use in the food industry.

• 환경위생공학
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• 제6권1호
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• pp.31-46
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• 1991

Aeromonas hydrophila which bacause various diseases in human also infects fresh water fish, severly damaging the fishing industries. To prevent disease in humans and reduce damaging on the fishing industries, We have examined several characteristics of Aeromonas hydrophila and obtained the following results. All of the strains gave a posive voges-proskauer, methyl-red, salicin and esculin reaction. Seventeen(94.4%) A. hydrophila strains presented the phenotype SP-PAB- in autoagglut-ination test, but only strain AH 997 showed $SP^{+}PAB^{+}$. in autoagglut ination test, but only strain AH 997 $SP^{+}PAB^{+}$ All of the strains took up the censored to various degrees. Three of 18 strains showed positive reaction in crystal violet binding test. Hemolytic activity ranged from titers of 0 to 1/256. Seven of the 17(38.8%) A. hydrophila strains were positive in sucking mouse assay. Cytotoxin activity on vero and RK cells was displayed various titers.(1/2-1/1024)

• Archives of Pharmacal Research
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• 제28권9호
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• pp.1031-1036
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• 2005

[ $(+)-Lyoniresinol-3{\alpha}-O-\beta-D-glucopyranoside$ ] (1) was isolated from an ethyl acetate extract of the root bark from Lycium chinense Miller, and its structure was determined using 1D and 2D NMR spectroscopy including DEPT, HMQC, and HMBC. $(+)-Lyoniresinol-3{\alpha}-O-\beta-D-glucopyranoside$ exhibited potent antimicrobial activity against antibiotic-resistant bacterial strains, methicillin-resistant Staphylococcus aureus (MRSA) isolated from patients, and human pathogenic fungi without having any hemolytic effect on human erythrocytes. In particular, compound 1 induced the accumulation of intracellular trehalose on C. albicans as stress response to the drug, and disrupted the dimorphic transition that forms pseudo-hyphae caused by the pathogenesis. This indicates that $(+)-Lyoniresinol-3{\alpha}-O-\beta-D-glucopyranoside$ has excellent potential as a lead compound for the development of antibiotic agents.

• 대한수의학회지
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• 제39권5호
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• pp.1028-1032
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• 1999

Alpha toxin of S aureus has cytolytic activity respectively. This antigen has been received the most attention since it is a major virulence factor in pathogenesis of staphylococcal mastitis. Thus, alpha toxin has been focused as potential candidate of vaccine to minimize mastitis in cows. The purpose of this study was to develop a simple, efficient production and purification methods of sufficient amount of alpha toxin antigen from S aureus. Alpha toxin production measured by hemolytic activity was the highest at 18 hrs postinoculation in yeast extract culture medium supplemented with thiamine, nicotinic acid and casamino acid. Alpha toxin was purified by ammonium sulfate precipitation (65%) and ultrafiltration. Molecular weight of the toxin was 33 kDa in the analysis with SDS-PAGE. Conclusionally, when alpha toxin was included in the vaccine, the optimal harvest time of alpha toxin was at 18 hrs after inoculation in yeast extract medium supplemented with thiamine and nicotinic acid.