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A Fluorescent Supramolecular Biosensor for Bacterial Detection via Binding-Induced Changes in Coiled-Coil Molecular Assembly
摘要： The essential elements required for any sensors are a receptor, a signal converter, and a detector. Here, we report the construction of bacterial biosensors in which all of the required biosensor elements are furnished in one supramolecular assembly. The supramolecular biosensor is based on a double-layered octa-helical coiled-coil peptide assembly that contains tetravalent bioreceptors on the outer surface and environment-sensitive fluorophores in the core. The signal conversion takes advantage of the noncovalent and reversible nature of the self-assembled system, i.e., the multivalent binding of bacteria induces conformational changes in the supramolecular state, which is translated into differential fluorescence emissions. We show that fluorescent supramolecular biosensors (fSBs) can selectively detect E. coli over other bacteria. Because the fSBs were resistant to heat-induced denaturation, they retained their bacterial-sensing capability even at an elevated temperature (50 ℃). Biosensors based on responsive supramolecular assemblies can be further developed to detect various large and flat biological objects and biomacromolecules.
关键词： Escherichia coli,Supramolecule,Biosensor,Bacteria,Self-assembly,Peptide-based probe
更新于2025-11-21 11:08:12
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Novel ELISA based on fluorescent quenching of DNA-stabilized silver nanoclusters for detecting E. coli O157:H7
摘要： Escherichia coli O157:H7 (E. coli O157:H7) is a potential threat to human health; thus, a rapid and sensitive method for detecting it is necessary. We designed a single-stranded DNA that contained an appended block and anchoring block. The appended block acted as a scaffold to prepare fluorescent Ag nanoclusters (AgNCs). The anchoring block contained Poly A, which bound with the surface of gold nanoparticles to quench the fluorescence of AgNCs. An interesting ELISA approach for detecting E. coli O157:H7 was established via fluorescent quenching of DNA-stabilized AgNCs by using a sandwich complex. The changes in fluorescence intensity of AgNCs were used to quantitatively detect E. coli O157:H7. The sensitivity for detecting E. coli O157:H7 reached 1.905 × 10^3 CFU/mL with a good linear range. Compared with conventional ELISA, the sensitivity of this technique increased by 30-fold. Moreover, this method demonstrated specificity and reproducibility and could be used in food samples.
关键词： Fluorescence quenching,Ag nanoclusters,Escherichia coli O157:H7,Gold nanoparticles
更新于2025-09-23 15:23:52
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Ultraviolet-C irradiation for reducing <i>Escherichia coli</i> and <i>Salmonella</i> sp. on asparagus spears
摘要： This research was to study on the decontamination of two foodborne pathogenic bacteria (Escherichia coli and Salmonella sp.) on asparagus spears using ultraviolet-C (UV-C) irradiation. Fresh asparagus spears were inoculated with each suspension of Escherichia coli or Salmonella sp. (105 CFU mL-1). The sample was compared with the effect of UV-C irradiation for 1 min after inoculated each bacterial species, which was compared to fresh asparagus spears (control). Asparagus spears were packed in foam trays, wrapped with PVC films (14 μm thickness). The packages were stored at 10°C (85% RH) for 9 days. Escherichia coli, Salmonella sp., total microbial, yeast and molds counts on asparagus spears were enumerated during storage. Fresh asparagus spears had an initial Escherichia coli count of 2.4 log CFU g-1, whereas Salmonella sp. count was about 1.8 log CFU g-1. UV-C irradiation did not reduce both of Escherichia coli and Salmonella sp. count of asparagus spears inoculated with Escherichia coli or Salmonella sp. compared to un-irradiated inoculated sample. After storage at 10°C, UV-C irradiation reduced Escherichia coli count to about 0.1 log CFU g-1 on day 6, whereas it reduced Salmonella sp. counts of asparagus spears inoculated with Salmonella sp. about 1.0 log CFU g-1. Total microbial and fungi counts of all asparagus spears were increased during storage. UV-C irradiation delayed microbial and fungi count compared to un-irradiated sample.
关键词： asparagus,UV-C,Salmonella sp.,Escherichia coli
更新于2025-09-23 15:22:29
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Single-molecule imaging of DNA gyrase activity in living <i>Escherichia coli</i>
摘要： Bacterial DNA gyrase introduces negative supercoils into chromosomal DNA and relaxes positive supercoils introduced by replication and transiently by transcription. Removal of these positive supercoils is essential for replication fork progression and for the overall unlinking of the two duplex DNA strands, as well as for ongoing transcription. To address how gyrase copes with these topological challenges, we used high-speed single-molecule fluorescence imaging in live Escherichia coli cells. We demonstrate that at least 300 gyrase molecules are stably bound to the chromosome at any time, with ～12 enzymes enriched near each replication fork. Trapping of reaction intermediates with ciprofloxacin revealed complexes undergoing catalysis. Dwell times of ～2 s were observed for the dispersed gyrase molecules, which we propose maintain steady-state levels of negative supercoiling of the chromosome. In contrast, the dwell time of replisome-proximal molecules was ～8 s, consistent with these catalyzing processive positive supercoil relaxation in front of the progressing replisome.
关键词： Escherichia coli,transcription,DNA gyrase,replication,supercoiling,single-molecule imaging
更新于2025-09-23 15:21:21
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Efficient photocatalytic inactivation of Escherichia coli by Mn-CdS/ZnCuInSe/CuInS2 Quantum Dots-Sensitized TiO2 nanowires
摘要： A novel visible light-driven photocatalyst (represented as Mn-CdS/ZCISe/CIS/TiO2) for the passivation of Escherichia coli (E. coli) was prepared with TiO2 nanowires as support and CuInS2 (CIS), ZnCuInSe (ZCISe) quantum dots (QDs), and Mn-doped CdS (Mn-CdS) nanoparticles (NPs) as sensitizers. The use of CIS, ZCISe QDs and Mn-CdS NPs extends the light harvest region to visible light. The photoelectric conversion efficiency was consequently improved with a photocurrent density of 12.5 mA/cm2, about 60 times that of the pure TiO2 nanowires. The germicidal efficiency of the photocatalyst was assess by passivation of E. coli, 96% bacteria in 50 mL 105 colony forming units (CFU)/mL solution were killed within 50 min. Besides the high efficiency, the composite has good stability and satisfactory recycling performance. The antibiotic mechanism was also performed by using photoluminescence and scavenging agent of different active matter, revealing that the photo-generated holes play a major role in the sterilization process.
关键词： Quantum dots,Escherichia coli,TiO2,Photocatalysis
更新于2025-09-23 15:21:01
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[IEEE 2018 IEEE 8th International Conference Nanomaterials: Application & Properties (NAP) - Zatoka, Ukraine (2018.9.9-2018.9.14)] 2018 IEEE 8th International Conference Nanomaterials: Application & Properties (NAP) - The Study of the Activation of Antibacterial Activity of Silver Nanoparticles by Laser Radiation
摘要： Silver nanoparticles are known to have inhibitory and bactericidal effects and they play a significant role in the development of new antimicrobial substances against pathogenic microorganisms. In this article the minimum bactericidal concentration of the silver nanoparticles on two different bacteria cultures (Escherichia coli and Staphylococcus aureus) as well as the possibility to enhance their antimicrobial activity using laser irradiation was investigated. It was found, that solutions of silver nanoparticles at concentrations ≥ 3120 μg/ml cause death of both types of studied microorganisms. Dispersion of nanoparticles after laser irradiation caused the inhibition of Staphylococcus aureus at lower concentrations.
关键词： surface plasmon resonance,Escherichia coli,Staphylococcus aureus,bactericidal properties,silver nanoparticles
更新于2025-09-23 15:21:01
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Antibacterial activity of ZnO nanoparticles fabricated using laser ablation in solution technique
摘要： The zinc oxide (ZnO) nanoparticles have been produced by using laser ablation in solution technique, resulting nanoparticles with hexagonal wurtzite structure and the size range of 20 – 50 nm. The optical characterization has predicted the nanoparticles band gap at least 3.16 eV. The ZnO nanoparticles were employed as an antibacterial agent for the growth of Escherichia coli (E. coli), and it shows a great potential. Total plate count (TPC) analysis was conducted by applying the ZnO nanoparticles with different concentration of 5%, 10%, 15%, 20%, 25% and 30% (portion of bacteria medium). The 5% concentration could reduce more than half of the E. coli population after 24 hours incubation time. There was no living bacteria detected for 20%, 25% and 30% ZnO concentration.
关键词： ZnO nanoparticles,laser ablation,antibacterial activity,Escherichia coli
更新于2025-09-23 15:19:57
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EXPRESS: Cyclic Changes in the Amide Bands Within <i>Escherichia coli</i> Biofilms Monitored Using Real-Time Infrared Attenuated Total Reflection Spectroscopy
摘要： Contrary to the planktonic state of bacteria, their biofilm form represents severe complications in areas such as human medicine or food industry due to the increasing resistance against harsh conditions and treatment. In the present study, infrared attenuated total reflection (IR-ATR) spectroscopy has been applied as an analytic tool studying Escherichia coli (E. coli) biofilm formation close to real time. We report on IR spectroscopic investigations on the biofilm formation via ATR waveguides probing the biofilm in the spectral window of 1800–900 cm?1 at dynamic flow conditions, which facilitated monitoring the growth dynamics during several days. Key IR bands are in the range 1700–1590 cm?1 (amide I), 1580–1490 cm?1 (amide II), and 1141–1006 cm?1 extracellular polymeric substances (EPS), which were evaluated as a function of time. Cyclic fluctuations of the amide I and amide II bands and a continuous increase of the EPS band were related to the starvation of bottom-layered bacteria caused by the nutrient gradient. Potential death of bacteria may then result in cannibalistic behavior known for E. coli colonies. Observing this behavior via IR spectroscopy allows revealing these cyclical changes in bottom-layered bacteria within the biofilm under continuous nutrient flow, in molecular detail, and during extended periods for the first time.
关键词： bacteria,starvation,Escherichia coli,EPS,IR-ATR spectroscopy,amide band,biofilm,infrared attenuated total reflectance
更新于2025-09-19 17:15:36
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A novel short-term high-lactose culture approach combined with a matrix-assisted laser desorption ionization-time of flight mass spectrometry assay for differentiating Escherichia coli and Shigella species using artificial neural networks
摘要： Background Escherichia coli is currently unable to be reliably differentiated from Shigella species by routine matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis. In the present study, a reliable and rapid identification method was established for Escherichia coli and Shigella species based on a short-term high-lactose culture using MALDI-TOF MS and artificial neural networks (ANN). Materials and methods The Escherichia coli and Shigella species colonies, treated with (Condition 1)/without (Condition 2) a short-term culture with an in-house developed high-lactose fluid medium, were prepared for MALDI-TOF MS assays. The MS spectra were acquired in linear positive mode, with a mass range from 2000 to 12000 Da and were then compared to discover new biomarkers for identification. Finally, MS spectra data sets 1 and 2, extracted from the two conditions, were used for ANN training to investigate the benefit on bacterial classification produced by the new biomarkers. Results Twenty-seven characteristic MS peaks from the Escherichia coli and Shigella species were summarized. Seven unreported MS peaks, with m/z 2330.745, m/z 2341.299, m/z 2371.581, m/z 2401.038, m/z 3794.851, m/z 3824.839 and m/z 3852.548, were discovered in only the spectra from the E. coli strains after a short-term high-lactose culture and were identified as belonging to acid shock protein. The prediction accuracies of the ANN models, based on data set 1 and 2, were 97.71±0.16% and 74.39±0.34% (n = 5), with an extremely remarkable difference (p < 0.001), and the areas under the curve of the receiver operating characteristic curve were 0.72 and 0.99, respectively. Conclusions In summary, adding a short-term high-lactose culture approach before the analysis enabled a reliable and easy differentiation of Escherichia coli from the Shigella species using MALDI-TOF MS and ANN.
关键词： MALDI-TOF MS,Escherichia coli,high-lactose culture,artificial neural networks,Shigella species
更新于2025-09-16 10:30:52
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A host dTMP-bound structure of T4 phage dCMP hydroxymethylase mutant using an X-ray free electron laser
摘要： The hydroxymethylation of cytosine bases plays a vital role in the phage DNA protection system inside the host Escherichia coli. This modification is known to be catalyzed by the dCMP hydroxymethylase from bacteriophage T4 (T4dCH); structural information on the complexes with the substrate, dCMP and the co-factor, tetrahydrofolate is currently available. However, the detailed mechanism has not been understood clearly owing to a lack of structure in the complex with a reaction intermediate. We have applied the X-ray free electron laser (XFEL) technique to determine a high-resolution structure of a T4dCH D179N active site mutant. The XFEL structure was determined at room temperature and exhibited several unique features in comparison with previously determined structures. Unexpectedly, we observed a bulky electron density at the active site of the mutant that originated from the physiological host (i.e., E. coli). Mass-spectrometric analysis and a cautious interpretation of an electron density map indicated that it was a dTMP molecule. The bound dTMP mimicked the methylene intermediate from dCMP to 5′-hydroxymethy-dCMP, and a critical water molecule for the final hydroxylation was convincingly identified. Therefore, this study provides information that contributes to the understanding of hydroxymethylation.
关键词： hydroxymethylation,XFEL,dCMP hydroxymethylase,X-ray free electron laser,T4dCH,hydroxylation,cytosine bases,phage DNA protection,dTMP,Escherichia coli,bacteriophage T4,methylene intermediate
更新于2025-09-12 10:27:22