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Inactivation of Bacteria during Stimulation of Sensitizers with High-Power Nanosecond Laser Pulses
摘要： The results of a study of photoinactivation of bacteria during stimulation of sensitizers with nanosecond laser pulses with a power density within 1–30 MW/cm2 are presented. The irreversible damage to living cells by shock waves developed during the formation and collapse of vapor bubbles in locally heated microregions of the medium is discussed. The local heating of the medium occurred due to heat release during nonradiative relaxation of high electronic states of sensitizer molecules.
关键词： local heating,highly excited electronic states of molecules,photoinactivation of bacteria,acoustic waves
更新于2025-09-16 10:30:52
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Development and validation of an alternative parameter for quantification of signals emitted by fluorescently labelled bacteria in microscopic images
摘要： In this study, an alternative parameter for quantifying the signals of fluorescently labelled bacteria (e.g. propidium iodide, Cyanine 3, etc.) in microscopic images was investigated. Three common parameters (mean grey value (MGV), mean grey value which is corrected for the background (MGVcwB) and the signal to background ratio (SBR) per bacterial cell) are used as reference parameters. As an alternative, the coefficient of variation (CV) is defined as the ratio of the logarithm of the standard deviation and the logarithm of the mean grey value of a bacterial cell in a microscopic image. The actual fluorescence value was safeguarded by measuring commercially available fluorescence latex microspheres at regular time intervals within our study. The precision and the correlation of the respective values of MGV, MGVcwB, SBR and CV taken from identical images were measured and subsequently normalized in order to enhance the inter-parameter comparability. The average precision of CV was the highest (89% ± 14) with decreasing numbers for MGVcwB, SBR, and MGV (78% ± 25, 71% ± 32, and, 52% ± 22, respectively). Changes in operational parameters, e.g., microscope settings, protocol steps, etc., yielded good results for the CV but less precise results for MGV, MGVcwB, and SBR in the analyses of identical images. In conclusion, using the alternative parameter CV, changes in the composition of microbial ecosystems may thus be investigated at the highest precision level.
关键词： Microscopic images,Mean grey value,Signal to background ratio,Fluorescently labelled bacteria,Coefficient of variation
更新于2025-09-16 10:30:52
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Bacterial identification by lipid profiling using liquid atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry
摘要： Background: In recent years, mass spectrometry (MS) has been applied to clinical microbial biotyping, exploiting the speed of matrix-assisted laser desorption/ionization (MALDI) in recording microbe-specific MS profiles. More recently, liquid atmospheric pressure (AP) MALDI has been shown to produce extremely stable ion flux from homogenous samples and ‘electrospray ionization (ESI)-like’ multiply charged ions for larger biomolecules, whilst maintaining the benefits of traditional MALDI including high tolerance to contaminants, low analyte consumption and rapid analysis. These and other advantages of liquid AP-MALDI MS have been explored in this study to investigate its potential in microbial biotyping. Methods: Genetically diverse bacterial strains were analyzed using liquid AP-MALDI MS, including clinically relevant species such as Escherichia coli, Staphylococcus aureus and Klebsiella pneumoniae. Bacterial cultures were subjected to a simple and fast extraction protocol using ethanol and formic acid. Extracts were spotted with a liquid support matrix (LSM) and analyzed using a Synapt G2-Si mass spectrometer with an in-house built AP-MALDI source. Results: Each species produces a unique lipid profile in the m/z range of 400–1100, allowing species discrimination. Traditional (solid) MALDI MS produced spectra containing a high abundance of matrix-related clusters and an absence of lipid peaks. The MS profiles of the bacterial species tested form distinct clusters using principle component analysis (PCA) with a classification accuracy of 98.63% using a PCA-based prediction model. Conclusions: Liquid AP-MALDI MS profiles can be sufficient to distinguish clinically relevant bacterial pathogens and other bacteria, based on their unique lipid profiles.
关键词： matrix-assisted laser desorption/ionization,mass spectrometry,bacteria,profiling,speciation,MALDI,biotyping,lipids
更新于2025-09-16 10:30:52
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The molecular mechanisms of light adaption in light-harvesting complexes of purple bacteria revealed by a multiscale modeling
摘要： The light-harvesting in photosynthetic purple bacteria can be tuned in response to the light conditions during cell growth. One of the used strategies is to change the energy of the excitons in the major light-harvesting complex, commonly known as LH2. In the present study we report the first systematic investigation of the microscopic origin of the exciton tuning using three complexes, namely the common (high-light) and the low-light forms of LH2 from Rps. acidophila plus a third complex analogous to the PucD complex from Rps. palustris. The study is based on the combination of classical molecular dynamics of each complex in a lipid membrane and excitonic calculations based on a multiscale quantum mechanics/molecular mechanics approach including a polarizable embedding. From the comparative analysis, it comes out that the mechanisms that govern the adaptation of the light conditions use the different H-bonding environment around the bacteriochlorophyll pigments to dynamically control both internal and inter-pigment degrees of freedom. While the former have a large effect on the site energies, the latter significantly change the electronic couplings, but only the combination of the two effects can fully reproduce the tuning of the final excitons and explain the observed spectroscopic differences.
关键词： purple bacteria,H-bonding environment,multiscale modeling,light-harvesting complexes,excitonic tuning
更新于2025-09-16 10:30:52
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[OSA Optical Fiber Sensors - Lausanne (2018..-..)] 26th International Conference on Optical Fiber Sensors - Towards a Single Parameter Sensing for Bacteria Sorting through Optical Fiber Trapping and Back-Scattered Signal Analysis
摘要： We investigated if a recently proposed method can differentiate yogurt bacteria trapped by a polymeric lensed fiber tip, through back-scattered signal analysis. Results suggest that it can be a valuable contribution for foodborne analysis/bacteria identification.
关键词： optical fiber trapping,foodborne analysis,bacteria sorting,back-scattered signal analysis
更新于2025-09-16 10:30:52
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The in vivo mechanics of the magnetotactic backbone as revealed by correlative FLIM-FRET and STED microscopy
摘要： Protein interaction and protein imaging strongly benefit from the advancements in time-resolved and superresolution fluorescence microscopic techniques. However, the techniques were typically applied separately and ex vivo because of technical challenges and the absence of suitable fluorescent protein pairs. Here, we show correlative in vivo fluorescence lifetime imaging microscopy F?rster resonance energy transfer (fLiM-fRet) and stimulated emission depletion (SteD) microscopy to unravel protein mechanics and structure in living cells. We use magnetotactic bacteria as a model system where two proteins, MamJ and MamK, are used to assemble magnetic particles called magnetosomes. The filament polymerizes out of MamK and the magnetosomes are connected via the linker MamJ. Our system reveals that bacterial filamentous structures are more fragile than the connection of biomineralized particles to this filament. More importantly, we anticipate the technique to find wide applicability for the study and quantification of biological processes in living cells and at high resolution.
关键词： FLIM-FRET,living cells,magnetotactic bacteria,STED microscopy,protein mechanics
更新于2025-09-12 10:27:22
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Detection of <i>Escherichia coli</i> O157:H7 with Antibody Conjugated Amino-Functionalized Graphene Quantum Dots as Immunofluorescence Probes
摘要： Escherichia coli O157: H7 (E. coli O157: H7) is a foodborne pathogenic bacterium which can cause fever, diarrhoea and vomiting in humans. Thus, a rapid, simple, and specific bioprobe for pathogen detection in contaminated foods has been attracted more and more attention. In this work, the strong fluorescent amino-functionalized graphene quantum dots (af-GQDs) were prepared by hydrothermal method. The microtopographic height, surface morphology and spectroscopic properties of af-GQDs are characterized by the high resolution transmission electron microscope (HRTEM), atomic force microscope (AFM), UV-vis, fluorescence, Raman spectroscopic techniques. All the results showed that the af-GQDs can be effectively applied in the preparation of biocompatible immunofluorescence probe and in the detection of E. coli O157: H7. The minimum detection limit is 100 cfu/mL. It is a simple, rapid, sensitive, low-cost and easy to be popularized method, which provides a feasible way to monitor E. coli O157: H7 in food safety.
关键词： E. coli O157: H7,Bioprobe,Amino-functionalized graphene quantum dots,Foodborne bacteria,Immunofluorescence
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Mobile Based in Situ Detection of Live/Dead and Antibiotic Resistant Bacteria by Silver Nanorods Array Sensor Fabricated by Glancing Angle Deposition
摘要： The rapid in-situ detection of viability of bacteria is essential for human health and environmental care. It has become one of the biggest needs in biological and medical sciences to prevent infections and diseases, which usually occur in hospitals and field clinics. Nowadays, antibiotic resistance (ABR) has been grown as one of the world’s acutest public health problems, which requires a quick and efficient solution. Here, we demonstrate an easy, sensitive, user-friendly, portable, cost effective and time saving approach for detection of live, dead and drug resistant bacteria. Most of the organisms are found to produce H2S gas by their metabolism system. The endogenous H2S evolution was targeted to differentiate between live and dead as well as ABR bacteria. The silver nanorods (AgNRs) arrays sensors were fabricated by glancing angle deposition technique. The colorimetric and water wettability (contact angle) features of as-synthesized AgNRs were found to be highly sensitive and selective for hydrogen sulfide (H2S) gas. E.coli, P. aeruginosa, B. subtilis and S. aureus were used as the model organisms for this study. A drastic visible change in color as well as wetting properties of AgNRs array was observed. To make it easy, a user friendly and field deployable android based mobile app ‘Colorimetric Detector’ was developed. This dual mode detection is facile, inexpensive and can be easily scaled-up in the field of disease diagnosis.
关键词： mobile app,colorimetric detection,silver nanorods,antibiotic resistance,bacteria detection,H2S gas
更新于2025-09-11 14:15:04
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Bacteria-assisted synthesis of nanosheets-assembled TiO2 hierarchical architectures for constructing TiO2-based composites for photocatalytic and electrocatalytic application
摘要： Synthesis and application of three-dimensional TiO2 hierarchical architectures are one of the major priorities in the research and development of TiO2 catalysts. Using bacteria as template and reactor, a bioinspired strategy was developed in the present study to synthesize nanosheets-assembled TiO2 hierarchical architectures (N-TiO2-HA) and relative composites for photocatalytic and electrocatalytic application. In the first part of this work, three kinds of bacteria were used for the synthesis of N-TiO2-HA with satisfactory mono-dispersity, and the growth mechanism was investigated. In the second part, the porous TiO2 hollow spheres (P-TiO2-HS), which were obtained by calcining N-TiO2-HA at 750 oC in air, were incorporated with MIL-101(Fe) to improve the visible-light photocatalytic efficiency. The results of photo-Fenton assisted degradation of rhodamine B and ciprofloxacin indicate that the synthesized composites have excellent visible-light photocatalytic activity. In the third part, the nanosheets-assembled TiO2-carbon hollow spheres (N-TiO2-C-HS), which were obtained by calcining N-TiO2-HA at 750 oC in argon atmosphere, were electrodeposited with Pt for electrocatalytic oxidation of methanol. The electrochemical measurements show that Pt-deposited N-TiO2-C-HS have better electrocatalytic activity, stability, and tolerance to CO poisoning than commercial Pt/C catalysts.
关键词： nanosheets,TiO2 hierarchical architectures,photocatalysis,bacteria,electrocatalytic oxidation of methanol
更新于2025-09-11 14:15:04
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A Paper-Based Biological Solar Cell
摘要： A merged system incorporating paperfluidics and papertronics has recently emerged as a simple, single-use, low-cost paradigm for disposable point-of-care (POC) diagnostic applications. Stand-alone and self-sustained paper-based systems are essential to providing effective and lifesaving treatments in resource-constrained environments. Therefore, a realistic and accessible power source is required for actual paper-based POC systems as their diagnostic performance and portability rely significantly on power availability. Among many paper-based batteries and energy storage devices, paper- based microbial fuel cells have attracted much attention because bacteria can harvest electricity from any type of organic matter that is readily available in those challenging regions. However, the promise of this technology has not been translated into practical power applications because of its short power duration, which is not enough to fully operate those systems for a relatively long period. In this work, we for the first time demonstrate a simple and long-lasting paper-based biological solar cell that uses photosynthetic bacteria as biocatalysts. The bacterial photosynthesis and respiration continuously and self-sustainably generate power by converting light energy into electricity. With a highly porous and conductive anode and an innovative solid-state cathode, the biological solar cell built upon the paper substrates generated the maximum current and power density of 65 μA/cm2 and 10.7 μW/cm2, respectively, which are considerably greater than those of conventional micro-sized biological solar cells. Furthermore, photosynthetic bacteria in a 3-D volumetric chamber made of a stack of papers provided stable and long-lasting electricity for more than 5 h, while electrical current from the heterotrophic culture on 2-D paper dramatically decreased within several minutes.
关键词： photosynthetic bacteria,microbial fuel cells,paper-based point-of-care diagnostic devices,solar energy harvesting,paper-based biological solar cells
更新于2025-09-11 14:15:04