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The recent growth of fast-fashion and our daily use of fibrous materials over the years have led to the massive release of microfibers (MF) into the oceans. Although MF pollution is commonly linked to plastic pollution, a vast majority of the collected MF are made of natural components. We investigated the effects of a 96h-exposure to both natural and synthetic textile MF and their associated chemical additives on the physiology of C. gigas. Selected MF were either produced in the lab from six commercial yarns (acrylic, nylon and polyester (synthetic MF); wool, cotton and organic cotton (natural MF)) or originating from the laundering of jumpers made of polyester, cotton or a mix of MF (polyester/cotton/acrylic). Specifically, we evaluated oyster's capacity of ingesting MF of a given size and explored the effects of both MF and their leachates on a set of biomarkers representing key physiological functions. For both MF and leachates, two scenarios were considered: an environmentally relevant (10 MF.L-1) and a worst-case scenario (10000 MF.L-1). Overall, when comparing laboratory-produced and laundering MF, a distinctive response was observed. There was no effect of laboratory-produced MF exposure concentration on oyster's key physiological processes whereas a dose-dependent effect was observed in oysters exposed to MF from washing machines. In addition, the exposure to both laundering MF and leachates disturbed oysters' digestive function, and this, regardless the nature of MF, while a more contrasting response was observed in the case of laboratory-produced MF. Ingestion of natural calibrated MF led to a perturbation of oyster digestive functions, presumably due to their physical characteristics (roughness), while little effects of synthetic MF were observed on the selected endpoints. These results stress the need to consider realistic wastes in ecotoxicological studies, including natural and non-calibrated particles to thoroughly evaluate the impact of anthropogenic debris. Also see: https://micro2022.sciencesconf.org/426823/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano

Hydrothermal vents are located on the mid-ocean ridges, and are characterized by challenging physico-chemical conditions. Despite these conditions dense hydrothermal communities develop down around hydrothermal fluid emissions. The presence of marine invertebrates relies on their capacity to cope with these challenging factors, and, for those forming most of the biomass, on their ability to live in symbiosis with chemoautotrophic bacteria. Bathymodiolus azoricus is one of these symbiotic species that harbors two types of γ-proteobacteria, a sulfide-oxidizing bacterium (SOX) (using the oxidation of H2S as the source of energy and CO2 as source of carbon) and a methane-oxidizing bacterium (MOX) (that uses the oxidation of CH4 as both a source of energy and carbon). These bacteria are located in specific epithelial cells in the gill tissue of the mussel. The proportion and number of these symbiont types (SOX vs. MOX) in B.azoricus can change in response to environmental conditions, and especially on the relative concentration of reduced compounds. The aim of our study is to understand the molecular mechanisms of acquisition, regulation and maintenance of the symbiotic charge in B .azoricus gills. We therefore, performed a global OMICs analysis (proteomics –nano LC-MS/MS and transcriptomics- micro-array) on mussels from natural population (Lucky Strike, -1700m) and on mussels that experimentally loose or maintain their symbiotic rate. This exploratory approach was followed by a more specific approach on family of proteins involved in immunity process and/or in host/symbiont interactions. This PhD provides hypotheses on the mechanisms governing the relationship and communication between host and symbionts.; L'importance des symbioses dans l'évolution du vivant est désormais admise et les associations symbiotiques sont observées dans une grande diversité d'habitats. Notre étude porte sur une symbiose au sein d'un écosystème réduit, les sources hydrothermales de l'océan profond. Bathymodiolus azoricus est un bivalve hydrothermal vivant le long de la ride Médio-Atlantique, qui héberge dans des cellules branchiales spécialisées, deux types de γ-protéobactéries différentes : des méthanotrophes (MOX) et des sulfo-oxydantes (SOX). Ces dernières sont capables d'oxyder les composés réduits présents dans le fluide hydrothermal fournissant ainsi énergie et/ou source de carbone à leur hôte. Cette double endosymbiose est plastique ainsi, l'abondance relative du type de symbionte hébergé (SOX vs. MOX) varie en fonction des concentrations en composés réduits présent dans le milieu (H2S, CH4). L'objectif de ce travail de thèse est d'identifier les acteurs moléculaires impliqués dans l'acquisition, le maintien et la régulation des bactéries symbiotiques. Pour ce faire, une analyse OMICs globale (protéomique -nano LC-MS/MS- et transcriptomique -micro-array-) a été mise en ¿uvre sur des individus symbiotiques issus de population naturelle (site hydrothermal Lucky Strike, -1700m) et sur des individus ayant expérimentalement perdu ou maintenu leurs symbiotes. Suite à cette approche globale et exploratoire, une approche plus spécifique a été menée sur des familles de protéines impliquées dans des processus immunitaire et/ou d'interactions hôte/symbiotes. Cette thèse apporte un éclaircissement sur les mécanismes régissant les relations et la communication hôte/symbiote.

Hydrothermal vents are located on the mid-ocean ridges, and are characterized by challenging physico-chemical conditions. Despite these conditions dense hydrothermal communities develop down around hydrothermal fluid emissions. The presence of marine invertebrates relies on their capacity to cope with these challenging factors, and, for those forming most of the biomass, on their ability to live in symbiosis with chemoautotrophic bacteria. Bathymodiolus azoricus is one of these symbiotic species that harbors two types of γ-proteobacteria, a sulfide-oxidizing bacterium (SOX) (using the oxidation of H2S as the source of energy and CO2 as source of carbon) and a methane-oxidizing bacterium (MOX) (that uses the oxidation of CH4 as both a source of energy and carbon). These bacteria are located in specific epithelial cells in the gill tissue of the mussel. The proportion and number of these symbiont types (SOX vs. MOX) in B.azoricus can change in response to environmental conditions, and especially on the relative concentration of reduced compounds. The aim of our study is to understand the molecular mechanisms of acquisition, regulation and maintenance of the symbiotic charge in B .azoricus gills. We therefore, performed a global OMICs analysis (proteomics –nano LC-MS/MS and transcriptomics- micro-array) on mussels from natural population (Lucky Strike, -1700m) and on mussels that experimentally loose or maintain their symbiotic rate. This exploratory approach was followed by a more specific approach on family of proteins involved in immunity process and/or in host/symbiont interactions. This PhD provides hypotheses on the mechanisms governing the relationship and communication between host and symbionts.; L'importance des symbioses dans l'évolution du vivant est désormais admise et les associations symbiotiques sont observées dans une grande diversité d'habitats. Notre étude porte sur une symbiose au sein d'un écosystème réduit, les sources hydrothermales de l'océan profond. Bathymodiolus azoricus est un bivalve hydrothermal vivant le long de la ride Médio-Atlantique, qui héberge dans des cellules branchiales spécialisées, deux types de γ-protéobactéries différentes : des méthanotrophes (MOX) et des sulfo-oxydantes (SOX). Ces dernières sont capables d'oxyder les composés réduits présents dans le fluide hydrothermal fournissant ainsi énergie et/ou source de carbone à leur hôte. Cette double endosymbiose est plastique ainsi, l'abondance relative du type de symbionte hébergé (SOX vs. MOX) varie en fonction des concentrations en composés réduits présent dans le milieu (H2S, CH4). L'objectif de ce travail de thèse est d'identifier les acteurs moléculaires impliqués dans l'acquisition, le maintien et la régulation des bactéries symbiotiques. Pour ce faire, une analyse OMICs globale (protéomique -nano LC-MS/MS- et transcriptomique -micro-array-) a été mise en ¿uvre sur des individus symbiotiques issus de population naturelle (site hydrothermal Lucky Strike, -1700m) et sur des individus ayant expérimentalement perdu ou maintenu leurs symbiotes. Suite à cette approche globale et exploratoire, une approche plus spécifique a été menée sur des familles de protéines impliquées dans des processus immunitaire et/ou d'interactions hôte/symbiotes. Cette thèse apporte un éclaircissement sur les mécanismes régissant les relations et la communication hôte/symbiote.