About a life cycle of a bacterial biofilm: from its birth to its possible killing. A study with the eyes of the physical chemist.

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Analyse par RMN du carbone-13 assistée par ordinateur de mélanges complexes : application aux essences issues de la transformation des combustibles fossiles et à la caractérisation de polymères acryliques

Non disponible / Not availableAprès quelques rappels de spectroscopie RMN, le principe du logiciel d'analyse automatique de mélanges complexes est présenté: il s'agit de transformer le spectre expérimental en spectre de bâtons puis de soustraire du spectre total chaque raie identifiée. Dans le cas de pics fortement enchevêtrés, des algorithmes de desenchevêtrement sont employés. Le logiciel repose sur l'existence d'une bibliothèque de déplacements chimiques du carbone-13 et il est montré comment il est possible de réaliser cette bibliothèque pour des produits spécifiques d'une même famille directement dans le mélange. La méthode est ensuite appliquée aux essences issues des procèdes de transformation du charbon et du pétrole. L'analyse individuelle des produits aromatiques est réalisée et les résultats sont comparés à ceux obtenus par CG-SM. Grâce a ces résultats, la modélisation de la fraction saturée peut être réalisée sans séparation chromatographique préalable. Enfin, cette méthode est appliquée à la caractérisation de la microstructure des polymères acryliques. En effet certains signaux RMN du carbone-13 sont sensibles aux effets de configuration et de composition de la chaine mais sont enchevêtrés. Une méthodologie basée sur la comparaison des résultats expérimentaux et théoriques obtenus par des lois statistiques grâce à la simulation des spectres permet l'attribution et la quantification des différents signaux

In situ spectroscopic analysis of Lactobacillus rhamnosus GG flow on an abiotic surface reveals a role for nutrients in biofilm development

International audienceIn this work, infrared spectroscopy was used to monitor the changes in the biochemical composition of biofilms of the probiotic bacterium Lactobacillus rhamnosus GG (LGG) in three nutritive media (10-fold diluted MRS, AOAC, and mTSB), in situ and under flow conditions. Epifluorescence microscopy was used to observe the shape of LGG cells and their distribution on the surface. Spectroscopic fingerprints recorded as a function of time revealed a medium-dependent content of nucleic acids, phospholipids and polysaccharides in the biofilms. In addition, time-dependent synthesis of lactic acid was observed in MRS/10 and AOAC/10. Polysaccharides were produced to the highest extent in mTSB/10, and the biofilms obtained were the densest in this medium. The rod shape of the cells was preserved in MRS/10, whereas acidic stress induced in AOAC/10 and the nutritional quality of mTSB/10 led to strong morphological changes. These alterations due to the nutritive environment are important to consider in research and use of LGG biofilms

Effect of the nutritive medium choice on the formation of Lactobacillus rhamnosus GG biofilms on an abiotic surface

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Infrared and Raman spectra of uranyl(VI) oxo-hydroxo complexes in acid aqueous solutions: a chemometric study

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Discrepancies between Cyclic and Linear Antimicrobial Peptide Actions on the Spectrochemical and Nanomechanical Fingerprints of a Young Biofilm

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Infrared and Raman spectroscopic study of carboxylic acids in heavy water

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Analysis of changes in attenuated total reflection FTIR fingerprints of Pseudomonas fluorescens from planktonic state to nascent biofilm state

International audienceAttenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy is a useful method for monitoring biofilm in situ, non-destructively, in real time, and under fully hydrated conditions. In this work we focused on changes in Pseudomonas fluorescens ATR-FTIR fingerprint accompanying the very early stages of biofilm formation: initial bacterial adhesion and the very beginning of biofilm development in the presence of nutrients. To help interpreting variations in the ATR-FTIR fingerprint of sessile bacteria, ATR-FTIR spectra of planktonic bacteria in different growth phases were also examined, and the average surface coverage and spatial arrangement of bacteria on the ATR crystal were determined by epifluorescence microscopy. The proteins, nucleic acids and polysaccharides ATR-FTIR spectral data recorded during growth of sessile bacteria were shown to be linked to changes in the physiological state of the bacteria, possibly accompanied by extracellular polymeric substances production. This work clearly showed by spectroscopic method how bacteria change drastically their metabolism during the first hours of biofilm formation