Synthesis of azafluorenones and related compounds using deprotocupration-aroylation followed by intramolecular direct arylation

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.International audienceThe efficiency of the deprotocupration-aroylation of 2-chloropyridine using lithiocuprates prepared from CuX (X=Cl, Br) and LiTMP (TMP=2,2,6,6-tetramethylpiperidido, 2 equiv) was investigated. CuCl was identified as a more suitable copper source than CuBr for this purpose. Different diaryl ketones bearing a halogen at the 2 position of one of the aryl groups were synthesized in this way from azines and thiophenes. These were then involved in palladium-catalyzed ring closure: substrates underwent expected CH-activation-type arylation to afford fluorenone-type compounds, and were also subjected to cyclization reactions leading to xanthones, notably in the presence of oxygen-containing substituents or reagents

Bacterial interactions in a marine mudflat biofilm: a Pseudomonas bacterium produces a proteinaceous molecule inhibiting the biofilm formation of a flavobacterium strain

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Colonisation de deux interfaces par des bactéries marines issues d'un biofilm benthique transitoire et d'un biofilm composite " microorganismes / produits de corrosion " permanent.

International audienceEn environnement marin, les biofilms microbiens recouvrent la plupart des surfaces solides. Lors de la formation des biofilms, la colonisation des interfaces par les microorganismes est progressive et suit une logique taxonomique et/ou fonctionnelle des espèces. Ces biofilms représentent des systèmes multi-cellulaires au sein desquels se produisent de nombreuses interactions, de compétitions et coopérations complexes encore mal comprises et que nous souhaitons explorer. Dans le cadre de ce travail, nous nous intéressons à deux types de biofilms, un biofilm benthique prélevé sur la vasière intertidale de Brouage et un biofilm formé sur acier dans le port des Minimes de La Rochelle, impliqué dans la biocorrosion des structures métalliques. L'objectif de ce travail est d'étudier les interactions bactériennes au sein de ces biofilms. Une large gamme de bactéries hétérotrophes cultivables (160) a été isolée de ces biofilms. Leur capacité à former des biofilms a été évaluée en faisant varier les interfaces de colonisation (surfaces abiotiques en verre ou en polystyrène) et les conditions de développement des biofilms (statique ou dynamique). Dans un premier temps, nous avons testé, en conditions statiques, la capacité des bactéries à adhérer aux 2 interfaces et à se développer ensuite en biofilm. Dans un deuxième temps, les 9 souches les plus aptes à établir un biofilm sur les 2 interfaces ont été testées en conditions dynamiques (chambre à flux) sur une interface en verre. Les 4 bactéries présentant les propriétés les plus intéressantes (stabilité du biofilm, architecture 3D...) ont été sélectionnées et serviront de modèles pour l'exploration des interactions microbiennes

Caractérisation des substances polymériques extracellulaires (EPS) de biofilms de diatomées benthiques marines

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Cell-bound exopolysaccharides from an axenic culture of the intertidal mudflat Navicula phyllepta diatom affect biofilm formation by benthic bacteria

International audienceAt low tide, intertidal mudflat biofilms cover large surfaces and are mainly responsible for the high productivity of these marine areas. In the European Atlantic coast, such biofilms are mainly composed of diatoms, especially Navicula phyllepta, bacteria, and microbial extracellular polymeric substances (EPS). To better understand interactions occurring between microorganisms, we first axenized a N. phyllepta culture with a new and simple protocol. Colloidal and bound EPS secreted by diatom cells during the exponential growth and the stationary phase were then harvested, and we tested their effects on the in vitro formation of biofilms by three marine bacteria. The latter had been isolated from a French Atlantic intertidal mudflat and were previously selected for their strong in vitro biofilm-forming ability. They belong to the Flavobacterium, Roseobacter, and Shewanella genera. Navicula phyllepta-bound EPS synthesized during the stationary phase specifically inhibited the biofilm formation by the Flavobacterium sp. strain, whereas they stimulated biofilm development by the two other strains. The EPS acted in all cases during the first stages of the biofilm establishment. Saccharidic molecules were found to be responsible for these activities. This is the first report on marine bacterial antibiofilm saccharides of microalgal origin. This work points out the complexity of the benthic natural biofilms with specific microalgae/bacteria interactions and underlines the possibility to use axenic diatoms as a source of bioactive compounds

Marine bacteria from the French Atlantic coast displaying high forming-biofilm abilities and different biofilm 3D architectures

International audienceFew studies have reported the species composition of bacterial communities in marine biofilms formed on natural or on man-made existing structures. In particular, the roles and surface specificities of primary colonizers are largely unknown for most surface types. The aim of this study was to obtain potentially pioneering bacterial strains with high forming-biofilm abilities from two kinds of marine biofilms, collected from two different surfaces of the French Atlantic coast: an intertidal mudflat which plays a central role in aquaculture and a carbon steel structure of a harbour, where biofilms may cause important damages

On the bacterial communities associated with the corrosion product layer during the early stages of marine corrosion of carbon steel

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Caractérisation des substances polymériques extracellulaires (EPS) de biofilms de diatomées benthiques marines

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