Microalgae within biofilm Metagenome

Freshwater biofilms are a complex natural assemblage of microorganisms, including microalgae and bacteria. These microorganisms live together in symbiosis in an exopolymeric substance matrix. Biofilms are essential in the ecology and biochemistry of aquatic systems, and are defined to be one of the entries of mercury (Hg) in the trophic chain. The aim of this study was to enhance the knowledge on Hg bioaccumulation process in biofilms. To that end, Hg uptake kinetics was followed in freshwater biofilms of different ages and colonized in the Geneva Lake water and exposed in microcosms to Hg for 24 h. The biofilm composition was characterized by amplicon sequencing to identify predominant phyla associated with bacteria and microalgae. The obtained results demonstrated that the difference in Hg uptake by biofilms is due to difference in their community composition and microstructure (thickness).