• Journal of Microbiology and Biotechnology
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• 제17권2호
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• pp.226-233
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• 2007

Members of Methylobacterium, referred as pink-pigmented facultative methylotrophic bacteria, are frequently associated with terrestrial and aquatic plants, tending to form aggregates on the phyllosphere. We report here that the production of autoinducer molecules involved in the cell-to-cell signaling process, which is known as quorum sensing, is common among Methylobacterium species. Several strains of Methylobacterium were tested for their ability to produce N-acyl-homoserine lactone (AHL) signal molecules using different indicators. Most strains of Methylobacterium tested could elicit a positive response in Agrobacterium tumefaciens harboring lacZ fused to a gene that is regulated by autoinduction. The synthesis of these compounds was cell-density dependent, and the maximal activity was reached during the late exponential to stationary phases. The bacterial extracts were separated by thin-layer chromatography and bioassayed with A. tumefaciens NTI (traR, tra::lacZ749). They revealed the production of various patterns of the signal molecules, which are strain dependent. At least two signal molecules could be detected in most of the strains tested, and comparison of their relative mobilities suggested that they are homologs of N-octanoyl-$_{DL}$-homoserine lactone ($C_8-HSL$) and N-decanoyl-$_{DL}$-homoserine lactone ($C_{10}-HSL$).

• 미생물학회지
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• 제50권2호
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• pp.128-136
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• 2014

Acyl homoserine lactone (AHL) 분해효소인 lactonase는 높은 기질 특이성을 지니기 때문에 경제적이고 효율적인 쿼럼 저해 기술로 이용될 가능성을 지니고 있다. 본 연구에서는 Chromobacterium violaceum CV026과 Agrobacterium tumefaciens NTL4를 바이오센서로 이용하여 biofouling이 일어난 역삼투막 시료로부터 쿼럼 센싱과 관련된 생물막 형성을 억제하는 6종의 균주를 분리 연구하였다. 분리된 균주는 모두 Bacillus 속으로 동정되었으며, AHL 분자의 acyl 사슬 길이나 치환 종류에 상관 없이 쿼럼 저해활성을 보여주었다. 균주들은 Pseudomonas aeruginosa PAO1에 의한 생물막 형성을 46.7-58.3% 정도 감소시켰으며 이 때 저해물질은 열처리에 민감한 특성을 보여주었다. 분리 균주 중 RO1S-5를 이용하여 N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C12 AHL)과 반응시킨 결과, 상응하는 acyl homoserine (3-oxo-C12-HS)이 생성되는 것을 LC-MS로 확인하여 쿼럼 저해가 lactonase 활성에 의한 것임을 규명하였다. AHL 물질에 대한 높은 특이성 등을 감안할 때 분리 균주 RO1S-5는 생물막 형성과 관련된 질병이나 산업공정 중 발생하는 biofouling을 해결하는데 유용하게 쓰일 수 있을 것으로 기대된다.

• Journal of Microbiology and Biotechnology
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• 제11권5호
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• pp.804-811
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• 2001

In many Gram-negative bacteria, autoinducers, such as N-acyl-L-homoserine lactone(acyl-HSL) and its derivative molecules, mediate the cell-density-dependnet expression of certain operons. The current study identified the autoinducers produced by Burkholderia cepacia G4, a trichloroethylene-degrading lagoon isolate, using TLC bioassays with Agrobacterium tumefaciens NT1(pDCI141E33) and Chromobacterium violaceum CVO26, and a GC-MS analysis. The ${R_f}\;and\;{R_t}$ values and mass spectra were compared with those of synthetic compounds. Based on the analyses, it was confirmed that G4 produces N-hexanoyl (C6)-, N-octanoyl (C8)-, N-decanoyl (C10)-, N-dodecanoyl (C12)-HSL, and an unknown active species. The integration of the GC peak areas exhibited a ratio of C8-HSL:C10-HSL:C12-HSL at 3:17:1 with C6-HSL and C10-HSL production at trace and micromolar levels, respectively, in the culture supernatants. Nutants partially defective in producing acyl-HSLs were also partially defective in the biosynthesis of an antibiotic substance. These results indicate that the autoinducer-dependent gene regulation in G4 is dissimilar to the clinical B. cepacia strains isolated from patients with cystic fibrosis.

• 생명과학회지
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• 제18권2호
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• pp.206-212
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• 2008

인간이 서로 간의 의사소통을 위해 언어를 사용하듯이, 세균의 경우도 외부 환경 변화를 신속히 감지하여 서로 효과적으로 대응하기 위해서 주변 세포들과 소통할 수 있는 세균만의 독특한 화학적 언어를 사용하는 것으로 알려져 있다. 특히, 일정 세포 농도에 도달했을 때 자체적으로 생산된 화학적 신호를 통해 개체 수를 인지하고 그에 따라 특정 유전자의 발현을 동시에 조절하는 quorum sensing (QS) 기작은 다양한 세균 종들에서 광범위하게 존재한다. 본 연구는 다양한 천연물 추출물들을 대상으로 QS 저해 활성을 확인하였는데 QS 지시균주인 Agrobacterium tumefaciens NT1과 화학적으로 합성한 QS autoinducers을 사용한 bioassay를 수행하였다. 그 결과 양배추, 파, 양파의 추출물들에서 QS 저해 활성을 확인하였고, recycling preparative HPLC (prep-HPLC)를 통한 정제 과정을 통해, 83분 지점의 peak에 해당하는 성분들이 공통으로 QS 저해 활성을 가지고 있음을 확인하였다. 따라서 그 QS 저해 성분을 QSI-83으로 지정하고 thin layer chromatography (TLC)를 통해 P. syringae pv. tabaci의 autoinducers 합성을 저해하는 활성을 가지고 있음을 확인하였다. 또한 열에 대한 안정성과 세균 생장에서의 영향을 조사하였는데, 그 결과 QSI-83은 열에 안정하며 세균의 생장에는 영향을 끼치지 않는 물질임을 확인하였다. 따라서 우리는 천연물로부터 분리된 새로운 성분이 QS 저해제로서 이용될 수 있음을 제안한다.

• 미생물학회지
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• 제44권2호
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• pp.85-92
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• 2008

Pseudomonas aeruginosa는 기회 감염성 병원균으로, Cystic fibrosis, 미생물 감염성 각막염,화상 부위 2차 감염 등의 다양한 질병을 초래한다. 정족수 인식(쿼럼 센싱)이라고도 알려져 있는 세포간 신호전달 기전이 이러한 감염에서 중요한 역할을 하기 때문에 P. aeruginosa의 정족수 인식 시스템들이 집중적으로 연구되어 왔다. P. aeruginosa의 정족수 인식 시스템들을 소개하는 많은 문헌들이 주로 두 개의 주요 acyl-homoserine lactone (AHL) 계열 정족수 신호물질들인 N-3-oxododecanoyl homoserine lactone (3OC12)과 N-butanoyl homoserine lactone (C4)에 초점을 맞추어 설명하고 있지만, 실제로는 몇 가지 새로운 신호물질들이 발견되어져 왔고, 그들이 P. aeruginosa의 병독성과 신호전달에 중요한 역할을 할 수 있음이 제안되어져 왔다. 그 중 하나가 PQS(Pseudomonas quinolone signal; 2-heptyl-3-hydroxy-4-quinolone)인데, 이 물질은 현재 P. aeruginosa의 잘 규명된 주요 신호물질로 인식되고 있다. 이에 더하여, 최근의 연구들은 또 다른 가능성 있는 P. aeruginosa신호물질들을 제안해 왔는데, diketopiperazines (DKPs)과 pyocyanin이 그들이다. DKPs는 환형 dipeptide로써 이를 구성하는 아미노산의 종류에 따라 다양한 구조를 가진다. P. aeruginosa의 배양액에서 검출된 몇몇 DKPs들이 기존에는 AHL에만 특이적으로 반응한다고 알려졌던 Vibrio 랸�N갸 LuxR biosensor를 활성화 시킬 수 있다는 것이 발견되어 새로운 신호물질로 제안되었다. Pyocyanin (1-hydroxy-5-methyl-phenazine)은 P. aeruginosa가 생산하는 여러 phenazine 화합물들 중의 하나로써, 특징적인 청록색을 띄는 산화-환원 활성물질이다. 이 물질도 정체 성장기 동안 일부 정족수 인식의 조절을 받는 유전자들의 발현을 증가시키는 최종 신호 인자로 최근 제안되었으며, 그 신호는 또 다른 전사 조절 인자인 SoxR에 의해 매개된다고 제안되었다. 본 논문에서는 P. aeruginosa에서 새롭게 발견, 제안되고 있는 이들 신호 전달 물질들에 대해 자세히 다루어 보기로 한다.

• 한국미생물생명공학회:학술대회논문집
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• 한국미생물생명공학회 2003년도 2003 Annual Meeting, BioExhibition and International Symposium
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• pp.173-174
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• 2003

• Journal of Microbiology and Biotechnology
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• 제29권4호
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• pp.596-606
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• 2019

N-acyl-homoserine lactone quorum sensing (AHL-QS) has been shown to regulate many physiological behaviors in Serratia marcescens MG1. In the current study, the effects of AHL-QS on the biosynthesis of acid and neutral products by S. marcescens MG1 and its isogenic ${\Delta}swrI$ with or without supplementing exogenous N-hexanoyl-L-homoserine lactone ($C_6-HSL$) were systematically investigated. The results showed that swrI disruption resulted in rapid pH drops from 7.0 to 4.8, which could be restored to wild type by supplementing $C_6-HSL$. Furthermore, fermentation product analysis indicated that ${\Delta}swrI$ could lead to obvious accumulation for acidogenesis products such as lactic acid and succinic acid, especially excess acetic acid (2.27 g/l) produced at the early stage of fermentation, whereas solventogenesis products by ${\Delta}swrI$ appeared to noticeably decrease by an approximate 30% for acetoin during 32-48 h and by an approximate 20% for 2,3-butanediol during 24-40 h, when compared to those by wild type. Interestingly, the excess acetic acid produced could be removed in an AHL-QS-independent manner. Subsequently, quantitative real-time PCR was used to determine the mRNA expression levels of genes responsible for acidogenesis and solventogenesis and showed consistent results with those of product synthesis. Finally, by close examination of promoter regions of the analyzed genes, four putative luxI box-like motifs were found upstream of genes encoding acetyl-CoA synthase, lactate dehydrogenase, ${\alpha}$-acetolactate decarboxylase, and Lys-like regulator. The information from this study provides a novel insight into the roles played by AHL-QS in switching from acidogenesis to solventogenesis in S. marcescens MG1.

• The Plant Pathology Journal
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• 제29권2호
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• pp.182-192
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• 2013

Numerous root-associated bacteria (rhizobacteria) are known to elicit induced systemic resistance (ISR) in plants. Bacterial cell-density-dependent quorum sensing (QS) is thought to be important for ISR. Here, we investigated the role of QS in the ISR elicited by the rhizobacterium, Serratia marcescens strain 90-166, in tobacco. Since S. marcescens 90-166 produces at least three QS signals, QS-mediated ISR in strain 90-166 has been difficult to understand. Therefore, we investigated the ISR capacity of two transgenic tobacco (Nicotiana tabacum) plants that contained either bacterial acylhomoserine lactone-producing (AHL) or -degrading (AiiA) genes in conjunction with S. marcescens 90-166 to induce resistance against bacterial and viral pathogens. Root application of S. marcescens 90-166 increased ISR to the bacterial pathogens, Pectobacterium carotovorum subsp. carotovorum and Pseudomonas syringae pv. tabaci, in AHL plants and decreased ISR in AiiA plants. In contrast, ISR to Cucumber mosaic virus was reduced in AHL plants treated with S. marcescens 90-166 but enhanced in AiiA plants. Taken together, these data indicate that QS-dependent ISR is elicited by S. marcescens 90-166 in a pathogen-dependent manner. This study provides insight into QS-dependent ISR in tobacco elicited by S. marcescens 90-166.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권4호
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• pp.322-328
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• 2005

Acylhomoserine lactones (AHLs) are known to be the triggering molecules in the quorum sensing mechanism of many gram-negative bacteria. In order to detect AHL inhibitors that are potential biofilm inhibitors, a convenient and sensitive bioassay was developed based on the $\beta$-galactosidase activity ($\beta$-GAL) of a recombinant Agrobacterium tumefaciens strain. A series of commercially available AHLs were tested for inducing $\beta$-GAL at varying concentrations in agar-plate and liquid cultures of the reporter strain. All AHLs tested exhibited a concentration­dependent induction, and octanoyl homoserine lactone (OHL) showed the highest sensitivity with a detection limit of 0.1 nM in the liquid culture assay. When fimbrolide, a known quorum sensing inhibitor, was added, induction of $\beta$-GAL by OHL was repressed. The repression at a constant OHL concentration was dependent on the fimbrolide concentration with the detection limit below 1 ppm, indicating that this assay is a sensitive method for screening AHL inhibitors.

• The Plant Pathology Journal
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• 제27권3호
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• pp.242-248
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• 2011

Several soil bacteria were found to degrade N-Acylhomoserine lactones (NAHLs), thereby interfering with the bacterial quorum sensing system. In this research, fifteen strains of NAHL degrading rhizobacteria were isolated from potato rhizosphere. Based on phenotypic characteristics and 16S rDNA sequence analyses, the strains were identified as members of genera Bacillus, Streptomyces, Arthrobacter, Pseudomonas and Mesorhizobium. All tested isolates were capable to degrade both synthetic and natural NAHL produced by Pectobacterium carotovorum subsp. carotovorum (Pcc) strain EMPCC. In quorum quenching experiments selected isolates, especially Mesorhizobium sp., were markedly reduced the pathogenicity of Pcc strain EMPCC in potato tubers and totally suppressed tissue maceration on potato tubers. These led to consider the latter as a useful biocontrol agent against Pectobacterium spp.