Biology subjects

Noel, C.

Publications and source records attributed to Noel, C..

4 recordsLinked to original sources

bioRxiv2026

Integrating coastal microbiome observations for human, oyster and environmental protection

The Reseau dObservatoires de Microbiologie Environnementale integree (ROME) was a pilot study conducted in France from September 2020 to August 2023 aiming to establish a network of eDNA-based observatories across four estuarine ecosystems associated with oyster farming: the Bay of Veys (Normandy), the Bay of Brest (Brittany), Marennes-Oleron (Nouvelle-Aquitaine), and the Thau Lagoon (Occitania). Within a One Health framework, the study assessed the influence of river inputs on estuarine microbiome structuring and the emergence of microbiological hazards affecting human, aquaculture, and ecosystem health. Over 2,000 samples were collected during the study, including biweekly surface water and monthly adult oyster samples. Environmental nucleic acids were analysed using metabarcoding (bacterial and protist communities) and metagenomics (human RNA viruses). The coastal microbiome, including pathogenic and harmful taxa relevant to humans and aquatic invertebrates, was characterized. River influence on microbial community composition was examined through spatial comparisons of stations exposed to varying levels of freshwater runoff, while oysters acted as bio-integrators of local microbial diversity. Results revealed coherent coastal-to-offshore microbiome structuring across all ecosystems, with local variations linked to riverine inputs. eDNA metabarcoding allowed to detect a wide range of prokaryotic and eukaryotic pathogens, as well as harmful algal bloom (HAB) genera, several not captured by conventional monitoring. These findings demonstrate the potential of the ROME eDNA observatory network for high-resolution, integrative surveillance of microbial biodiversity and early detection of biological risks in estuarine environments.

genomics↗

bioRxiv2025

Diversity and predation capacities of Amoebozoa against opportunistic vibrios in contrasting Mediterranean coastal environments.

Free-living amoebae (FLA) are ubiquitous and can be found in many types of environments including soil, freshwater, air and marine environments. They feed on various microorganisms and can play an important role in the food web and its dynamics. We previously described that FLAs belonging to the Vannella genus from the oyster farming area of the Thau lagoon in France could establish stable interactions with Vibrionaceae and could play a role in the selection of some virulence factors, potentially influencing pathogen dynamics. To further investigate the ecological interactions between FLA populations and Vibrionaceae in Mediterranean coastal waters, we conducted monthly sampling for one year at three contrasting sites. Free-living amoebae populations were isolated by culturing water and sediment samples on different bacterial lawns, including E. coli or V. tasmaniensis, V. crassostreae and V. harveyi. Amoebozoan diversity was analyzed using v4-18S barcoding and revealed distinct communities between the sediment and the water column, with Vannellidae significantly enriched in the water column whereas Paramoebidae were significantly enriched in the sediments. Selection of grazers on different bacterial lawns revealed that V. tasmaniensis inhibited the growth of most Vannellidae, whereas V. crassostreae inhibited the growth of a large proportion of Paramoebidae. These differences were further confirmed in functional grazing assays using isolates belonging to each Amoebozoa taxonomic group. Overall, our results highlight the need for more comprehensive studies of the diversity and population dynamics of Amoebozoa in marine environments, and that the role of these diversified grazers in shaping vibrio communities is complex and still poorly characterized.

microbiology↗

bioRxiv2023

A human iPSC-based in vitro neural network formation assay to investigate neurodevelopmental toxicity of pesticides

Proper brain development is based on the orchestration of key neurodevelopmental processes, including the formation and function of neural networks. If at least one key neurodevelopmental process is affected by a chemical, an adverse outcome is expected. To allow a higher testing throughput than the guideline animal experiments, a developmental neurotoxicity (DNT) in vitro testing battery (DNT IVB) has been set up that includes a variety of assays, which model several key neurodevelopmental processes. Gap analyses of the DNT IVB revealed the need of a human-based assay to assess neural network formation and function (NNF). Therefore, here we established the human NNF (hNNF) assay. A co-culture comprised of human-induced pluripotent stem cell (hiPSC)- derived excitatory and inhibitory neurons, as well as primary human astroglia, was differentiated for 35 days on micro-electrode arrays (MEA) and spontaneous electrical activity, together with cytotoxicity, was assessed on a weekly basis after washout of the compounds 24 h prior to measurements. In addition to the characterization of the test system, the assay was challenged with 28 compounds, mainly pesticides, identifying their DNT potential by evaluation of specific spike-, burst- and network parameters. This approach confirmed the suitability of the assay for screening environmental chemicals. Comparison of benchmark concentrations (BMC) with an NNF in vitro assay (rNNF) based on primary rat cortical cells, revealed differences in sensitivity. Together with the successful implementation of hNNF data into a postulated stressor-specific adverse outcome pathway (AOP) network associated with a plausible molecular initiating event for deltamethrin, this study suggests the hNNF assay as a useful complement to the current DNT IVB.

pharmacology and toxicology↗

bioRxiv2018

New Insights into the Nature of Symbiotic Associations in Aphids: Initial Steps Involved in Aphid Gut Infection by Serratia symbiotica Bacteria

Symbiotic microorganisms are widespread in nature and can play a major role in the ecology and evolution of animals. The aphid-Serratia symbiotica bacterium interaction provides a valuable model to study mechanisms behind these symbiotic associations. The recent discovery of cultivable S. symbiotica strains having the possibility of free-living lifestyle allowed us to simulate their environmental acquisition by aphids to examine the mechanisms involved in this infection pathway. Here, after oral ingestion, we analyzed the infection dynamic of cultivable S. symbiotica strains during the hosts lifetime using qPCR and fluorescence techniques and determined the immediate fitness consequences of these bacteria on their new host. We further examined the transmission behavior and phylogenetic position of cultivable strains. Usually, S. symbiotica are considered as maternally-transmitted bacteria living within aphid body cavity and bringing some benefits to their hosts despite their costs. Otherwise, our study revealed that cultivable S. symbiotica are predisposed to establish a symbiotic association with new aphid host, settling in its gut. We showed that cultivable S. symbiotica colonized the entire aphid digestive tract following infection, after which the bacterium multiplied exponentially during aphid development. Our results further revealed that gut colonization by the bacteria induce a fitness cost to their hosts. Nevertheless, it appeared that they also offer an immediate protection against parasitoids. Interestingly, cultivable S. symbiotica seem to be extracellularly transmitted, possibly through the honeydew. These findings provide new insights into the nature of symbiosis in aphids and the mechanisms underpinning these interactions.\n\nImportanceFor the first time, our study provides experimental data that highlight a new kind of symbiotic associations in aphids. By successfully isolating microbial symbiont from aphids and by cultivating it in vitro in our laboratory, we established artificial association by simulating new bacterial acquisitions involved in aphid gut infection. Our results showed the early stages involved in this route of infection. Until now, Serratia symbiotica is considered as a maternally-transmitted aphid endosymbiont. Nevertheless, here, we showed that our cultivable strains having an intermediate status between a strict free-living bacterium and a facultative endosymbiont, occupy and replicate in aphid gut and seem to be transmitted over generations through an environmental transmission mechanism. Moreover, they are both parasites and mutualists given the context, as many of the endosymbionts in aphids. Our findings give new perception of associations involved in aphids symbiosis.

evolutionary biology↗