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111.
Low electron transfer efficiency from bacteria to electrodes remains one of the major bottlenecks that limit industrial applications of microbial fuel cells (MFCs). Elucidating biological mechanism of the electron transfer processes is of great help in improving the efficiency of MFCs. Here, we reported that Pseudomonas aeruginosa could use different electron shuttles in a MFC under different quorum sensing (QS) expression patterns. An electron shuttle (rather than phenazines) with a high mid-point potential of 0.20 V (vs. Ag/AgCl–KCl saturated electrode) was found to be the dominating shuttle in a wild-type P. aeruginosa strain. Strikingly, upon genetic overexpression of rhl QS system in this wild-type strain, the electron shuttle was substituted by phenazines (pyocyanin and phenazine-1-carboxylate, with a low mid-point potential of −0.17 V and −0.28 V, respectively), which directly resulted in an increase of about 1.6 times of the maximum current of the rhl overexpressed strain over the wild-type strain. Our result implied that manipulating electron transfer pathways to improve MFCs’ efficiency could be achieved by rewiring gene regulatory circuits, thus synthetic biology strategies would be adopted. 相似文献
112.
Boukraa M Sabbah M Soulère L El Efrit ML Queneau Y Doutheau A 《Bioorganic & medicinal chemistry letters》2011,21(22):6876-6879
New N-acylhomoserine lactone (AHL) analogues in which the amide function is replaced by a reverse-amide one have been studied as AHL QS modulators. The series of compounds consists of α-(N-alkyl-carboxamide)-γ-butyrolactones, α-(N-alkyl-sulfonamide)-γ-butyrolactones, and 2-(N-alkyl-carboxamide)-cyclopentanones and cyclopentanols. Most active compounds exhibited antagonist activities against LuxR reaching the 30 μM range. 相似文献
113.
Tsuji F Kobayashi K Okada M Yamaguchi H Ojika M Sakagami Y 《Bioorganic & medicinal chemistry letters》2011,21(13):4041-4044
The ComX pheromone is an isoprenoidal oligopeptide containing a modified tryptophan residue, which stimulates natural genetic competence in gram-positive bacteria, Bacillus. We have reported the structure of the ComXRO-E-2 pheromone, which is produced by the RO-E-2 strain of Bacillus subtilis. ComXRO-E-2 analogs with substituted amino acids and isoprenoid modified tryptophan residues (e.g., prenyl, geranyl, and farnesyl), were synthesized and examined for biological activity. These results indicate that Phe-Trp∗(Ger)-NH2 is the minimum pharmacophore of the ComXRO-E-2 pheromone. Furthermore, the length of the isoprenoid moiety (i.e., modification style), and the presence of double bonds, are crucial for biological activity. The modification style of the ComX pheromone is more important than the peptide sequence with respect to biological activity. 相似文献
114.
Uroz S Oger P Chhabra SR Cámara M Williams P Dessaux Y 《Archives of microbiology》2007,187(3):249-256
Abtsract
Comamonas strain D1 enzymatically inactivates quorum-sensing (QS) signal molecules of the N-acyl homoserine lactone (N-AHSL) family, and exhibits the broadest inactivation range of known bacteria. It degrades N-AHSL with acyl-side chains ranging from 4 to 16 carbons, with or without 3-oxo or 3-hydroxy substitutions. N-AHSL degradation yields HSL but not N-acyl homoserine: strain D1 therefore harbors an amidohydrolase activity. Strain D1
is the fifth bacterium species in which an N-AHSL amidohydrolase is described. Consistent with its N-AHSL degradation ability, strain D1 efficiently quenches various QS-dependent functions in other bacteria, such as violacein
production by Chromobacterium violaceum and pathogenicity and antibiotic production in Pectobacterium. 相似文献
115.
116.
Calibration-curve-free quantitative PCR: a quantitative method for specific nucleic acid sequences without using calibration curves 总被引:1,自引:0,他引:1
Tani H Kanagawa T Morita N Kurata S Nakamura K Tsuneda S Noda N 《Analytical biochemistry》2007,369(1):105-111
We have developed a simple quantitative method for specific nucleic acid sequences without using calibration curves. This method is based on the combined use of competitive polymerase chain reaction (PCR) and fluorescence quenching. We amplified a gene of interest (target) from DNA samples and an internal standard (competitor) with a sequence-specific fluorescent probe using PCR and measured the fluorescence intensities before and after PCR. The fluorescence of the probe is quenched on hybridization with the target by guanine bases, whereas the fluorescence is not quenched on hybridization with the competitor. Therefore, quench rate (i.e., fluorescence intensity after PCR divided by fluorescence intensity before PCR) is always proportional to the ratio of the target to the competitor. Consequently, we can calculate the ratio from quench rate without using a calibration curve and then calculate the initial copy number of the target from the ratio and the initial copy number of the competitor. We successfully quantified the copy number of a recombinant DNA of genetically modified (GM) soybean and estimated the GM soybean contents. This method will be particularly useful for rapid field tests of the specific gene contamination in samples. 相似文献
117.
Thomas Seviour Susan Hove Hansen Liang Yang Yin Hoe Yau Victor Bochuan Wang Marcel R. Stenvang Gunna Christiansen Enrico Marsili Michael Givskov Yicai Chen Daniel E. Otzen Per Halkj?r Nielsen Susana Geifman-Shochat Staffan Kjelleberg Morten S. Dueholm 《The Journal of biological chemistry》2015,290(10):6457-6469
The mechanism by which extracellular metabolites, including redox mediators and
quorum-sensing signaling molecules, traffic through the extracellular matrix of
biofilms is poorly explored. We hypothesize that functional amyloids, abundant
in natural biofilms and possessing hydrophobic domains, retain these
metabolites. Using surface plasmon resonance, we demonstrate that the
quorum-sensing (QS) molecules, 2-heptyl-3-hydroxy-4(1H)-quinolone and
N-(3-oxododecanoyl)-l-homoserine lactone, and the
redox mediator pyocyanin bind with transient affinity to functional amyloids
from Pseudomonas (Fap). Their high hydrophobicity predisposes
them to signal-amyloid interactions, but specific interactions also play a role.
Transient interactions allow for rapid association and dissociation kinetics,
which make the QS molecules bioavailable and at the same time secure within the
extracellular matrix as a consequence of serial bindings. Retention of the QS
molecules was confirmed using Pseudomonas aeruginosa PAO1-based
2-heptyl-3-hydroxy-4(1H)-quinolone and
N-(3-oxododecanoyl)-l-homoserine lactone reporter
assays, showing that Fap fibrils pretreated with the QS molecules activate the
reporters even after sequential washes. Pyocyanin retention was validated by
electrochemical analysis of pyocyanin-pretreated Fap fibrils subjected to the
same washing process. Results suggest that QS molecule-amyloid interactions are
probably important in the turbulent environments commonly encountered in natural
habitats. 相似文献
118.
Streptococcus mutans, a Gram positive facultative anaerobe, is one among the approximately seven hundred bacterial species to exist in human buccal cavity and cause dental caries. Quorum sensing (QS) is a cell-density dependent communication process that respond to the inter/intra-species signals and elicit responses to show behavioral changes in the bacteria to an aggressive forms. In accordance to this phenomenon, the S. mutans also harbors a Competing Stimulating Peptide (CSP)-mediated quorum sensing, ComCDE (Two-component regulatory system) to regulate several virulence-associated traits that includes the formation of the oral biofilm (dental plaque), genetic competence and acidogenicity. The QS-mediated response of S. mutans adherence on tooth surface (dental plaque) imparts antibiotic resistance to the bacterium and further progresses to lead a chronic state, known as periodontitis. In recent years, the oral streptococci, S. mutans are not only recognized for its cariogenic potential but also well known to worsen the infective endocarditis due to its inherent ability to colonize and form biofilm on heart valves. The review significantly appreciate the increasing complexity of the CSP-mediated quorum-sensing pathway with a special emphasis to identify the plausible drug targets within the system for the development of anti-quorum drugs to control biofilm formation and associated risks. 相似文献
119.
120.
A dual-step fluorescence resonance energy transfer-based quenching assay for screening of caspase-3 inhibitors 总被引:1,自引:0,他引:1
The control of cell death is an intricate process involving a multitude of intracellular modulators. Among these molecules, the caspases have a central role and have become an interesting group of enzymes in the current pharmaceutical industry. We have developed a novel dual-step fluorescence energy transfer-based separation-free assay method for the primary screening of caspase-3 inhibitors in vitro. This method relies on fluorescent europium(III)-chelate-doped nanoparticle donors coated with streptavidin in conjunction with a dual-labeled (N-terminal Alexa Fluor 680 fluorescent acceptor and C-terminal BlackBerry Quencher 650) caspase-3-specific peptide substrate modified with a biotinyl moiety. In the assay, the nanoparticle donor excites the fluorescent acceptor, whose emission is monitored with time-resolved measurements. The intensity of the acceptor reflects the activity of the enzyme because the intensity is controlled by the proximity of the quencher. Owing to the dual-step fluorescence resonance energy transfer, this method enables a sensitized fluorescence signal directly proportional to the extent of enzymatic activity with relatively background fluorescence-free measurements in the event of complete enzyme inhibition. The generic nanoparticle donors further promote versatility and cost-efficiency of the method. The performance evaluated as the inhibitor (Z-DEVD-FMK) dose-response curve (IC(50) value of approximately 12 nM) was in good agreement with that of the recent methods found in literature. This assay serves as a model application proving the feasibility of the europium-chelate-doped nanoparticle labels in a homogeneous assay for proteolytic activity. 相似文献