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International audience; Aim: Polyphenols, dietary compounds, have drawn increasing attention due to their ability to lower oxidative stress involved in many pathologies and due to their positive effects in modulation of redox cellular signalling pathways [1]. The objectives of our studies are to identify the compounds derived from polyphenols after cellular metabolization (neuronal cells and gut bacteria) and to highlight how these molecules can act beneficially on microbiota and prevent neurodegenerescence diseases [2]. A particular attention is paid on oxidized phenolic metabolites and their biological effects. Methods: Currently, we focus our work in the impact of 5-O-caffeoylquinic acid (5-CQA), a dietary phenolic compound with neuroprotective properties [3], on the growth and the metabolism of three intestinal bacterial species (Lactobacillus reuteri, Bacteroides fragilis and Bifidobacterium longum). In parallel, we determine the bioconversion of 5-CQA by these three bacteria in mono and co-cultures. We particularly use LC-ESI-MS 2 and a molecular networking approach (GNPS platform) [4] to identify the biotransformed metabolites (e.g. oxidized derivatives). In addition, electrochemical technics are helpful to study the redox mechanism of 5-CQA and to generate oxidized samples. Results: L. reuteri has shown capacity to biotransform 5-CQA notably into caffeic acid and its oxidized derivative quinone, and into 3-hydroxybenzoic acid, contrary to B. fragilis and B. longum which didn't show any ability. First experiments in co-cultures were also carried out. Conclusion and perspectives: We have demonstrated an oxidative pathway in the bioconversion of 5-CQA by L. reuteri. Further experiments will be carried out to show the role of native, oxidized and biotransformed dietary polyphenols in the gut-brain axis.

International audience; In the context of research for new cytotoxic compounds, obtaining bioactive molecules from renewable sources remain a big challenge. Microorganisms and more specifically Actinobacteria from original sources are well known for their biotechnological potential and are hotspots for the discovery of new bioactive compounds. The strain DP94 studied here had shown an interesting cytotoxic activity of its culture broth (HaCaT IC50 = 8.0 ± 1.5 μg/mL; B16 IC50 = 4.6 ± 1.8 μg/mL), which could not been explained by the compounds isolated in a previous work. The increase of the cytotoxic activity of extracts was investigated, based on a Taguchi L9 orthogonal array design, after DP94 culture in TY medium using two different vessels (bioreactor or Erlenmeyer flasks). Various culture parameters such as temperature, pH and inoculum ratio (%) were studied. For experiments conducted in a bioreactor, stirring speed was included as an additional parameter. Significant differences in the cytotoxic activities of different extracts on B16 melanoma cancer cell lines, highlighted the influence of culture temperature on the production of cytotoxic compound(s) using a bioreactor. A culture in Erlenmeyer flasks was also performed and afforded an increase of the production of the active compounds. The best conditions for the highest cytotoxicity (IC50 on B16 6 ± 0.5 μg/mL) and the highest yield (202.0 mg/L) were identified as pH 6, temperature 37°C and 5% inoculum.

International audience; Microbial diversity studies using small subunit (SSU) rRNA gene sequences continue to advance our understanding of biological and ecological systems. Although a good predictor of overall diversity, using this gene to infer the presence of a species in a sample is more controversial. Here, we present a detailed polyphasic analysis of 10 bacterial strains isolated from three coastal lichens Lichina confinis, Lichina pygmaea and Roccella fuciformis with SSU rRNA gene sequences identical to the type strain of Streptomyces cyaneofuscatus. This analysis included phenotypic, microscopic, genetic and genomic comparisons and showed that despite their identical SSU rRNA sequences the strains had markedly different properties, and could be distinguished as 5 different species. Significantly, secondary metabolites profiles from these strains were also found to be different. It is thus clear that SSU rRNA based operational taxonomy units, even at the most stringent cut-off can represent multiple bacterial species, and that at least for the case of Streptomyces, strain de-replication based on SSU gene sequences prior to screening for bioactive molecules can miss potentially interesting novel molecules produced by this group that is notorious for the production of drug-leads.

International audience; Recent studies have admitted that bacterial communities were an important united partner of mini-ecosystem lichen symbiosis. Lichen, moreover, is also a rich source of new bacterial lineages and novel bacterial compounds. Therefore, microorganism communities isolated from lichens became a significant subject as a great potential of natural product discovery. Paenibacillus odorifer, a bacterium belonging to Firmicutes, was isolated from Rhizocarpon geographicum, a particular popular crust-forming rock lichen. Assessing its optimal growth conditions was conducted to improve its metabolite production yield by measure of optical density (OD) and by analysis of its chemical profile via TLC, HPLC, LC-MS. Firstly, the parameters chosen for optimal culture were kind of medium, pH and temperature. Results revealed that the growth of P. odorifer was better at 250C using Gym Streptomyces liquid medium supplemented with CaCO3 at pH=7. Secondly, the fermentation was launched by applying the best conditions of bacterial growth. After the 3-day culture using a bioreactor, the supernatant and bacterial cells were separated by centrifugation and organic compounds were absorbed from supernatant by XAD-7 resin. The desorption from resin was carried outthrough several stages to collect raw extract. TLC, HPLC and LC-MS analyses highlighted that this extract was a rich source of metabolites. Then, the crude extract was fractionated via flash chromatography on a 40 g C18 reversed-phase column, using a gradient solvent system of CH3CN-H2O at 15 mL/min flow rate in 75 min. Two diketopiperazines were isolated from the fractions by applying semi-preparative HPLC (Prevail C18 column, various ratios of CH3CN) such as cyclo(L-Phe-L-Val) and cyclo(L-Phe-L-Ile). Correspondingly, fermentation of P. odorifercould produce valuable compounds for future research.