• 한국미생물·생명공학회지
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• 제32권1호
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• pp.1-10
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• 2004

Many bacteria monitor their population density and control the expression of specialized gene sets in response to bacterial cell density based on a mechanism referred to as quorum sensing. In all cases, quorum sensing involves the production and detection of extracellular signaling molecules, auto inducers, as which Gram-negative and Gram-positive bacteria use most prevalently acylated homoserine lactones and processed oligo-peptides, respectively. Through quorum-sensing communication circuits, bacteria regulate a diverse array of physiological functions, including virulence, symbiosis, competence, conjugation, antibiotic production, motility, sporulation, and biofilm formation. Many pathogens have evolved quorum-sensing mechanisms to mount population-density-dependent attacks to over-whelm the defense responses of plants, animals, and humans. Since these AHL-mediated signaling mechanisms are widespread and highly conserved in many pathogenic bacteria, the disruption of quorum-sensing system might be an attractive target for novel anti-infective therapy. To control AHL-mediated pathogenicity, several promising strategies to disrupt bacterial quorum sensing have been reported, and several chemicals and enzymes have been also investigated for years. These studies indicate that anti-quorum sensing strategies could be developed as possible alternatives of antibiotics.

• 미생물학회지
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• 제38권1호
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• pp.38-44
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• 2002

국내 분리 침습성 균주중선별된 S. pneumoniae KNIH1156 (type 19F)으로부터 페렴구균의 병원성 인자이며 항원학적으로 다양한 표면단백항원인 pneumococcal surface protein A (PspA)를 분리${\cdot}$정제하였다. 폐렴구균을 CDM-ET배지에서 배양하게 되면 배지내로 PspA가 방출된다는 점과 PspA가 인간의 lactoferrin에 특이적으로 결합한다는 사실을 이용하여 CDM-ET 배지에서 S. pneumoniae KNIH1156 을 배양한 후 배양액을 농축하여 lactoferrinaffinity chromatography에 통과시켜 PspA를 분리, 정제하였다. 정제 후 anti-PspA antiserum으로 PspA를 확인하여 순수분리, 정제되었음을 확인하였으며 또한 인간의 lactoferrin과의 결합능력을 유지하고 있음을 확인하였다. 순수하게 분리하여 정제된 PspA의 면역원성을 확인하기 위하여 ICR mice에 욕강주사하였을 때 $LD_{50}$ 가 $1{\times}10^{7.5}$ CFU/ml께서 $1{\times}10^{10}$ CFU/ml로 약 500배 중가함을 관찰하였다. 따라서 본 실험에서S. pneumoniae KNIH1156 으로부터 분리${\cdot}$ 정제한 PspA가 면역원성과 방어능을 가지고 있음을 확인할 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제32권2호
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• pp.220-227
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• 2022

The spread of antibiotic-resistant strains of Staphylococcus aureus, a gram-positive opportunistic pathogen, has increased due to the frequent use of antibiotics. Inhibition of the quorum-sensing systems of biofilm-producing strains using plant extracts represents an efficient approach for controlling infections. Torilis japonica is a medicinal herb showing various bioactivities; however, no studies have reported the anti-biofilm effects of T. japonica extracts against drug-resistant S. aureus. In this study, we evaluated the inhibitory effects of T. japonica ethanol extract (TJE) on biofilm production in methicillin-sensitive S. aureus (MSSA) KCTC 1927, methicillin-resistant S. aureus (MRSA) KCCM 40510, and MRSA KCCM 40511. Biofilm assays showed that TJE could inhibit biofilm formation in all strains. Furthermore, the hemolysis of sheep blood was found to be reduced when the strains were treated with TJE. The mRNA expression of agrA, sarA, icaA, hla, and RNAIII was evaluated using reverse transcription-polymerase chain reaction to determine the effect of TJE on the regulation of genes encoding quorum sensing-related virulence factors in MSSA and MRSA. The expression of hla reduced in a concentration-dependent manner upon treatment with TJE. Moreover, the expression levels of other genes were significantly reduced compared to those in the control group. In conclusion, TJE can suppress biofilm formation and virulence factor-related gene expression in MSSA and MRSA strains. The extract may therefore be used to develop treatments for infections caused by antibiotic-resistant S. aureus.

• The Plant Pathology Journal
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• 제36권6호
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• pp.608-617
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• 2020

The type III secretion system (T3SS) is a key virulence determinant in the infection process of Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). Pathogen constructs a type III apparatus to translocate effector proteins into host cells, which have various roles in pathogenesis. 4-Hydroxybenozic acid and vanillic acid were identified from root extract of Sedum middendorffianum to have inhibitory effect on promoter activity of hrpA gene encoding the structural protein of the T3SS apparatus. The phenolic acids at 2.5 mM significantly suppressed the expression of hopP1, hrpA, and hrpL in the hrp/hrc gene cluster without growth retardation of Pst DC3000. Auto-agglutination of Pst DC3000 cells, which is induced by T3SS, was impaired by the treatment of 4-hydroxybenzoic acid and vanillic acid. Additionally, 2.5 mM of each two phenolic acids attenuated disease symptoms including chlorosis surrounding bacterial specks on tomato leaves. Our results suggest that 4-hydroxybenzoic acid and vanillic acid are potential anti-virulence agents suppressing T3SS of Pst DC3000 for the control of bacterial diseases.

• The Plant Pathology Journal
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• 제39권3호
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• pp.235-244
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• 2023

Acidovorax citrulli (Ac) is a phytopathogenic bacterium that causes bacterial fruit blotch (BFB) in cucurbit crops, including watermelon. However, there are no effective methods to control this disease. YggS family pyridoxal phosphate-dependent enzyme acts as a coenzyme in all transamination reactions, but its function in Ac is poorly understood. Therefore, this study uses proteomic and phenotypic analyses to characterize the functions. The Ac strain lacking the YggS family pyridoxal phosphate-dependent enzyme, AcΔyppAc(EV), virulence was wholly eradicated in geminated seed inoculation and leaf infiltration. AcΔyppAc(EV) propagation was inhibited when exposed to L-homoserine but not pyridoxine. Wild-type and mutant growth were comparable in the liquid media but not in the solid media in the minimal condition. The comparative proteomic analysis revealed that YppAc is primarily involved in cell motility and wall/membrane/envelop biogenesis. In addition, AcΔyppAc(EV) reduced biofilm formation and twitching halo production, indicating that YppAc is involved in various cellular mechanisms and possesses pleiotropic effects. Therefore, this identified protein is a potential target for developing an efficient anti-virulence reagent to control BFB.

• Journal of Microbiology and Biotechnology
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• 제27권7호
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• pp.1242-1248
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• 2017

Several medicinal plants are ethnomedically used in Korea as agents for treating infection, anti-inflammation, and pain relief. However, beyond typical inhibitory effects on cell growth, little is known about the potential anti-biofilm activity of these herbs, which may help to prevent cavities and maintain good oral health. This study aimed to investigate the antimicrobial and anti-biofilm activities of the methanol extracts of 37 Korean medicinal plants against dental pathogens Streptococcus mutans and Candida albicans, which synergize their virulence so as to induce the formation of plaque biofilms in the oral cavity. The antimicrobial activities were investigated by broth dilution and disk diffusion assay. The anti-biofilm and antioxidant activities were evaluated based on the inhibitory effect against glucosyltransferase (GTase) and the DPPH assay, respectively. Among 37 herbs, eight plant extracts presented growth and biofilm inhibitory activities against both etiologic bacteria. Among them, the methanol extracts (1.0 mg/ml) from Camellia japonica and Thuja orientalis significantly inhibited the growth of both bacteria by over 76% and over 83% in liquid media, respectively. Minimum inhibitory concentration (MIC) values of these methanol extracts were determined to be 0.5 mg/ml using a disk diffusion assay on solid agar media. Biofilm formation was inhibited by more than 92.4% and 98.0%, respectively, using the same concentration of each extract. The present results demonstrate that the medicinal plants C. japonica and T. orientalis are potentially useful as antimicrobial and anti-biofilm agents in preventing dental diseases.

• 생약학회지
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• 제54권1호
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• pp.27-37
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• 2023

This research was conducted to investigate the comprehensive effects of methanol extract of Coptidis rhizoma (MECR) against oral pathogen. We studied the antibacterial, anti-biofilm, anti-gingipain and anti-inflammatory activity of MECR. The minimum bactericidal concentration (MBC) of MECR was 100 ㎍/mL against several oral pathogens. The formation of biofilm of Streptococcus mutans was reduced to 8.93~24.12% in the presence of 25 ㎍/mL of MECR. The gingipain activity of Porphyromonas gingivalis were reduced to 3.91~6.23% in case of Kgp and 5.73~7.78% in case of Rgp in the presence of 10 mg/mL of MECR. The expression of fadA mRNA, virulence factor of Fusobacterium nucleatum (F. nucleatum) was 3 folds decreased in the presence of 25 ㎍/mL of MECR. In case of YD-38 cells challenged with F. nucleatum, RQ values of IL-8 and IL-6 were reduced about 12 folds and 5.45 folds in the presence of 2 ㎍/mL of MECR. In case of RAW 264.7 murine cell challenged with F. nucleatum, RQ values of IL-1β and IL-6 were 2.52 folds and 2.55 folds reduced in the presences of 2 ㎍/mL of MECR. Conclusively, MECR showed potent antibacterial and anti-inflammatory effects against oral pathogenic bacteria.

• Journal of Microbiology and Biotechnology
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• 제30권4호
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• pp.571-582
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• 2020

Quorum sensing (QS)-mediated infections cause severe diseases in human beings. The control of infectious diseases by inhibiting QS using antipathogenic drugs is a promising approach as antibiotics are proving inefficient in treating these diseases. Marine fungal (Pestalotiopsis sydowiana PPR) extract was found to possess effective antipathogenic characteristics. The minimum inhibitory concentration (MIC) of the fungal extract against test pathogen Pseudomonas aeruginosa PAO1 was 1,000 ㎍/ml. Sub-MIC concentrations (250 and 500 ㎍/ml) of fungal extract reduced QS-regulated virulence phenotypes such as the production of pyocyanin, chitinase, protease, elastase, and staphylolytic activity in P. aeruginosa PAO1 by 84.15%, 73.15%, 67.37%, 62.37%, and 33.65%, respectively. Moreover, it also reduced the production of exopolysaccharides (74.99%), rhamnolipids (68.01%), and alginate (54.98%), and inhibited the biofilm formation of the bacteria by 90.54%. In silico analysis revealed that the metabolite of P. sydowiana PPR binds to the bacterial QS receptor proteins (LasR and RhlR) similar to their respective natural signaling molecules. Cyclo(-Leu-Pro) (CLP) and 4-Hydroxyphenylacetamide (4-HPA) were identified as potent bioactive compounds among the metabolites of P. sydowiana PPR using in silico approaches. The MIC values of CLP and 4-HPA against P. aeruginosa PAO1 were determined as 250 and 125 ㎍/ml, respectively. All the antivirulence assays were conducted at sub-MIC concentrations of CLP (125 ㎍/ml) and 4-HPA (62.5 ㎍/ml), which resulted in marked reduction in all the investigated virulence factors. This was further supported by gene expression studies. The findings suggest that the metabolites of P. sydowiana PPR can be employed as promising QS inhibitors that target pathogenic bacteria.

• 한국미생물·생명공학회지
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• 제44권2호
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• pp.218-226
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• 2016

헬리코박터 파이로리균은 인간의 위에 감염하여 위염, 위궤양, 심지어 위암을 포함한 다양한 위장 질환의 발생시키는 원인으로 알려져 있다. 이러한 헬리코박터균의 제균을 위해 항생제 치료법이 이용되고 있지만 이러한 항생제들에 대한 헬리코박터균의 내성 증가가 전세계적인 문제로 대두되고 있다. 보고들에 따르면, 천연물질인 plumbagin은 항균 및 항암 효과를 가지고 있는 것으로 알려져있다. 따라서 본 연구에서는 헬리코박터 표준균주(ATCC 49503)에 plumbagin을 처리한 후 항균효과를 확인하였으며, 세균의 성장 및 병원성과 관련된 다양한 물질들의 발현에 미치는 영향을 immunoblotting 및 RT-PCR 방법을 이용하여 조사하였다. plumbagin의 헬리코박터균 억제효과를 확인하기 위해 한천희석법과 액체배지희석법을 이용해 최소억제농도를 도출하였다. 위와 같은 Plumbagin에 의한 헬리코박터균의 억제기전을 이해하기 위하여 헬리코박터균에 plumbagin을 처리한 후 세균 의 증식과 관련된 물질들을 대상으로 RT-PCR을 수행한 결과 RNA polymerase subunit α (rpoA)의 mRNA 발현이 감소한 것을 확인하였다. 또한, 헬리코박터균에 plumbagin을 처리한 후 주요 병원성인자들의 발현을 조사한 결과 CagA와 VacA 독소들의 mRNA 및 단백질양이 감소한 것을 확인하였으며, 유레아제(ureA)와 부착단백(alpA)의 발현도 plumbagin 처리에 의해 감소한 것을확인하였다. 위와 같은 결과들을 토대로, plumbagin은 본 연구에서 밝힌 기전들을 통해 헬리코박터균의 성장, 감염 및 발병을 억제하는 것으로 사료된다.

• 생명과학회지
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• 제13권1호
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• pp.67-72
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• 2003

위염, 위궤양 및 위암의 원인 균인 Helicobacter pylori 가균체 표면에 다량 함유하며 주된 생존 인자이며 병원성 인자인 urease를 대장균에서 발현시키고 이 효소에 대한 항체 또는 기질과의 특이 상호 작용을 이용하여 두 단계의 간편한 방법에 의하여 정제하였다. 우선 anti-H. pylori Urease IgG-Sepharose column과 urea-Sepharose column을 각각 제조하고 DEAE-Sepharose 음이온 교환수지를 통하여 1차 정제한 시료를 각각 적용하고 제반 조건에서 용출시켰다. Anti-H. pylori urease IgG-Sepharose column의 경우에는 urease 시료가 너무 강력하게 결합함으로써 극단적인 pH조건에서만 용출이 가능함이 관찰되었으므로, 100 mM 탄산 완충액(pH 10.5)으로 최종 용출하였을 때 비교적 순수한 효소를 얻었으나, 비활성이 다소 감소된 것으로 나타났다. 한편, urea-Sepharose에 적용시킨 시료는 100 mM urea-HEB 완충액(pH 7.5)으로 비교적 용이하게 용출되어 비교적 높은 순도와 비활성의 urease 효소를 얻을 수 있었으나 이 경우에는 urease의 smaller subunit인 UreA peptide band의 강도가 다소 감소한 것이 관찰되었다.