(micro)Plastic biofilms: Keeping afloat by carving out a new niche

As pervasive and persistent pollutants, microplastics exist alongside vast microbial communities in nature. These hardy substrates accumulate rich polymeric matrices from their surroundings that in turn offer nutrition and protection to diverse communities and their theatre of activity, representing a new ecological niche. In our research to date, biofilm communities demonstrate no specificity to plastic polymers but appear rather to be more strongly shaped by spatial and temporal factors. Other synthetic substrates such as tyre wear, however, signal towards some form of community selection that may manifest in the presence of leachates from the polymer itself. Contrary to these biofilms, polyaromatic hydrocarbons appear to follow the opposite pattern, with adsorbed concentrations on plastic more strongly dictated by the type of plastic polymer than the environment itself. Although community specificity has not yet been evidenced among different plastic polymers, our studies show that microplastics might shape communities in a different way. As suggested by our detection of carotenoid synthesis pathways and photosynthetic gene clusters among microplastic biofilms, we postulate this new niche to shape a specific functional toolkit adaptive among its members as a product of prolonged exposure to UV radiation at the sea's surface. This opens exciting new avenues for further research into the functional capabilities of these biofilms and offers new perspective on their potential beyond subordinate processes such as biodegradation. Here, we present a synthesis of our collective research on microplastic biofilms, the factors that shape them, and their interactions with nature. Also see: https://micro2024.sciencesconf.org/558827/document