The role of microbiota in shaping host resilience to polluting heavy metals.

Anthropogenic impacts, such as heavy metal contamination (HMC), can profoundly affect the biology of mollusks inhabiting our coastal waters, with significant repercussions on their populations and the aquaculture sector that relies on them. This study aims to investigate the influence of microbiota in the survival of its host, the Manila clam Ruditapes philippinarum, when exposed to HMC. To this end, the native microbiota was removed from a population of clams living in a non-polluted environment in France (i.e. recipient population) and replaced with the microbiota from a donor population collected in a HMC habitat in Porto Marghera (Venice). Firstly, the recipient population was rendered quasi germ-free by removing the residing microbiome through an antibiotic protocol. Subsequently, two methodologies of microbiota transplantation were tested: one involving cohabitation between the two populations, and another consisting of feeding the recipient group a homogenate obtained from the donor crams. Six days post-transplant, the clams were exposed to HMC, and their survival, overall physiological well-being and gene expression responses were investigated. This preliminary study provides solid foundation for future research on the link between microbiota and clam stress resilience, offering a perspective of integration of ecological and molecular approaches to better cope with anthropogenic challenges.