Dipicolinic acid (DPA) is a specific molecule of bacterial spores which is essential to their resistance to various stresses such as ultraviolet (UV) exposure and to their germination. DPA has a particular photochemistry that remains imperfectly understood. In particular, due to its ability to absorb UVc radiation, it is likely to form in vitro a wide variety of photoproducts (DPAp) of which only about ten have been recently identified.
View Article and Find Full Text PDFJ Photochem Photobiol B
September 2022
In this study, we develop a characterization of bacterial spore resistance to NIR pulsed light under modalities traditionally used in multiphoton microscopy. Energy dose and laser power are both key parameters in spore and bacterial cell inactivation. Surprisingly, spores and vegetative cells seem to show a similar sensitivity to pulsed NIR, spores being only 2-fold more resistant than their vegetative counterparts.
View Article and Find Full Text PDFSpectrochim Acta A Mol Biomol Spectrosc
November 2022
Bacterial spores can cause significant problems such as food poisoning (like neurotoxin or emetic toxin) or serious illnesses (like anthrax or botulism). This dormant form of bacteria, made of several layers of barriers which provide extreme resistance to many abiotic stresses (radiation, temperature, pressure, etc.), are difficult to investigate in situ.
View Article and Find Full Text PDFIn this study, stationary and time-resolvedfluorescence signatures, were statistically and chemometrically analyzed among three typologies of Chardonnay wines (A, B and C) with the objectives to evaluate their sensitivity to acidic and polyphenolic changes. For that purpose, a dataset was built using Excitation Emission Matrices of fluorescence (N = 103) decomposed by a Parallel Factor Analysis (PARAFAC), andfluorescence decays (N = 22), mathematically fitted, using the conventional exponential modeling and the phasor plot representation. Wine PARAFAC component C4 coupledwith its phasor plot g and s values enable the description of malolactic fermentation (MLF) occurrence in Chardonnay wines.
View Article and Find Full Text PDFBacterial spores are among the most resistant forms of life on Earth. Their exceptional resistance properties rely on various strategies, among them the core singular structure, organization and hydration. By using elastic incoherent neutron scattering, we probed the dynamics of Bacillus subtilis spores to determine whether core macromolecular motions at the sub-nanosecond timescale could also contribute to their resistance to physical stresses.
View Article and Find Full Text PDFBacterial spores are extremely resistant life-forms that play an important role in food spoilage and foodborne disease. The return of spores to a vegetative cell state is a three-step process, these being activation, germination, and emergence. High-pressure (HP) processing is known to induce germination in part of the spore population and even to inactivate a high number of spores when combined with other mild treatments such as the addition of nisin.
View Article and Find Full Text PDFDuring slow freezing, spermatozoa undergo membrane alterations that compromise their ability of fertilizing. These alterations are cause either by cold shock or by the use of cryoprotectants known to be cytotoxic. However, little is known about the membrane changes that occurred during freezing.
View Article and Find Full Text PDFThe objective of this study is to identify the prevalence of vertebral fractures (VFs) and to measure the scanographic bone attenuation coefficient of the first lumbar vertebra (SBAC-L1) based CT-scan, a biomarker of bone fragility in patients with rheumatoid arthritis (RA) and ankylosing spondylitis (AS) and in a control group. This monocentric and retrospective study included patients with RA and AS, based on ACR/EULAR or New-York criteria, respectively. A control group was constituted.
View Article and Find Full Text PDFToday, there is no effective non-thermal method to inactivate unwanted bacterial spores in foods. High-Pressure (HP) process has been shown to act synergistically with moderate heating and the bacteriocin nisin to inactivate spores but the mechanisms have not been elucidated. The purpose of the present work was to investigate in depth the synergy of HP and nisin on various foodborne spore species and to bring new elements of understandings.
View Article and Find Full Text PDFA multivariate image is an image stack in which each pixel contains several variables. Such images are common in many fields (medicine, imaging microscopy, satellite imaging..
View Article and Find Full Text PDFIntroduction: Screening for osteoporosis is crucial in rheumatoid arthritis (RA) patients. The aim of this study was to assess the value of thoraco-abdomino-pelvic CT-derived bone mineral density (BMD) results in L1, compared to dual energy X-ray absorptiometry (DXA) results for osteoporosis screening in rheumatoid arthritis patients.
Methods: Consecutive RA patients who underwent a CT-scan and DXA within a 2-year period were retrospectively included.
Specific treatments combining high temperatures of up to 150 °C and moderate pressure of up to 0.6 MPa have been applied to Bacillus subtilis 168 spores conditioned at different a levels (between 0.10 and 0.
View Article and Find Full Text PDFBlue light (400-430 nm) is known to induce lethal effects in some species of fungi by photo-oxidation caused by the excitation of porphyrins but the mechanisms involved remain poorly understood. In this work, we exposed the yeast to a high density light flux with two-photon excitation (830 nm equivalent to a one-photon excitation around 415 nm) and used quasi real-time visualization with confocal microscopy to study the initiation and dynamics of photo-oxidation in subcellular structures. Our results show that the oxidation generated by light treatments led to the permeabilization of the plasma membrane accompanied by the sudden expulsion of the cellular content, corresponding to cell death by necrosis.
View Article and Find Full Text PDFTo study vertebral fracture (VF) prevalence and the scanographic bone attenuation coefficient of the first lumbar vertebra (SBAC-L1) on computed tomography scans (CT-scans) in systemic sclerosis patients. This monocentric retrospective study included patients followed from 2000 to 2014 and fulfilling ACR/EULAR 2013 criteria for systemic sclerosis and who underwent a thoracic or thoraco-abdomino-pelvic CT-scan during their follow-up. Clinical characteristics for sclerosis and osteoporosis risk factors were collected.
View Article and Find Full Text PDFBecause of the ability of foodborne pathogens to survive in low-moisture foods, their decontamination is an important issue in food protection. This study aimed to clarify some of the cellular mechanisms involved in inactivation of foodborne pathogens after drying and subsequent heating. Individual strains of Typhimurium, Senftenberg, and were mixed into whole milk powder and dried to different water activity levels (0.
View Article and Find Full Text PDFFluorescent Probes aimed at absorbing in the blue/green region of the spectrum and emitting in the green/red have been synthesized (as the form of dyads-pentads), studied by spectrofluorimetry, and used for cellular imaging. The synthesis of phthalocyanine-pyrene 1 was achieved by cyclotetramerization of pyrenyldicyanobenzene, whereas phthalocyanine-BODIPY 2c was synthesized by Sonogashira coupling between tetraiodophthalocyanine and meso-alkynylBODIPY. The standard four-steps BODIPY synthesis was applied to the BODIPY-pyrene dyad 3 starting from pyrenecarbaldehyde and dimethylpyrrole.
View Article and Find Full Text PDFDue to the ability of foodborne pathogens to survive in low moisture food, the decontamination of milk powder is an important issue in food protection. The safety of food products is, however, not always insured and the different steps in the processing of food involve physiological and metabolic changes in bacteria. Among these changes, virulence properties may also be affected.
View Article and Find Full Text PDFSalmonella Typhimurium and Cronobacter sakazakii are two foodborne pathogens involved in neonatal infections from milk powder and infant formula. Their ability to survive in low-moisture food and during processing from the decontamination to the dried state is a major issue in food protection. In this work, we studied the effects of the drying process on Salmonella Typhimurium and Cronobacter sakazakii, with the aim of identifying the drying parameters that could promote greater inactivation of these two foodborne pathogens.
View Article and Find Full Text PDFDrying is a common process which is used to preserve food products and technological microorganisms, but which is deleterious for the cells. The aim of this study is to differentiate the effects of drying alone from the effects of the successive and necessary rehydration. Rehydration of dried bacteria is a critical step already studied in starter culture but not for different kinetics and not for pathogens.
View Article and Find Full Text PDFIn this work, we investigated how a combination of ethanol and high temperature (70°C), affect the properties of the inner membrane of Bacillus subtilis spores. We observed membrane permeabilization for ethanol concentrations ≥50%, as indicated by the staining of the spores' DNA by the cell impermeable dye Propidium Iodide. The loss of membrane integrity was also confirmed by a decrease in the peak corresponding to dipicolinic acid using infrared spectroscopy.
View Article and Find Full Text PDFAn original high-pressure microscopy chamber has been designed for real-time visualization of biological cell growth during high isostatic (gas or liquid) pressure treatments up to 200 MPa. This new system is highly flexible allowing cell visualization under a wide range of pressure levels as the thickness and the material of the observation window can be easily adapted. Moreover, the design of the observation area allows different microscope objectives to be used as close as possible to the observation window.
View Article and Find Full Text PDFHydrostatic pressure plays a significant role in the distribution of life in the biosphere. Knowledge of deep-sea piezotolerant and (hyper)piezophilic bacteria and archaea diversity has been well documented, along with their specific adaptations to cope with high hydrostatic pressure (HHP). Recent investigations of deep-sea microbial community compositions have shown unexpected micro-eukaryotic communities, mainly dominated by fungi.
View Article and Find Full Text PDFVisualization of DNA and RNA quadruplex formation in human cells was demonstrated recently with different quadruplex-specific antibodies. Despite the significant interest in these immunodetection approaches, dynamic detection of quadruplex in live cells remains elusive. Here, we report on NaphthoTASQ (N-TASQ), a next-generation quadruplex ligand that acts as a multiphoton turn-on fluorescent probe.
View Article and Find Full Text PDFSubphthalocyanine (SubPc), a putative fluorophore for optical imaging (OI), was conjugated to chelating ligands (DOTA, DTPA) affording water-soluble conjugates complexed with (non-radioactive) metals relevant to the following medical imaging techniques/therapies: MRI (Gd), PET (Cu, Ga), SPECT (In, Ga, Lu), RIT (Cu, Lu, Y), and NCT (Gd). Magneto-optical properties of ditopic gadolinium species (and optical properties of other metal containing species) were examined (brightness (ε × ΦF) and relaxivity R1) and fluorescence confocal/biphoton microscopy studies were conducted.
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