Bioremediation of Isoproturon and Sulfamethazine : linking the microbial community composition to the degradation capacity

National audience

Inglés. The large use of xenobiotics (pesticides and veterinary antibiotics) in current agricultural practices calls for environmental studies evaluating their impact and methodological developments aiming at lowering their persistence in soil and aquatic environments. Bioremediation via the bioaugmentation of degrading microbial communities is a promising method to clear contaminated sites but needs further developments. Specifically, improvements in the understanding of how degrading microorganisms must overcome environmental filtering when introduced into a new environment, and how biotic interactions with the autochthonous microbial communities might shape their trajectories are needed in order to design efficient bioremediation strategies. Here we focused our research on two xenobiotics used in agricultural practices and frequently retrieved in soil and sediments: a recently banned herbicide: Isoproturon (IPU), and a veterinary antiobiotics : Sulfamethazin (SMZ).Agricultural soils and sediments from various geographical origins were screened for their capacity to degrade IPU and SMZ, respectively. To test the importance of biotic filtering, IPU and SMZ degrading microbial communities were extracted, using a suspension-dilution approach, and reciprocally inoculated into the other sterilized environmental matrix. Degrading microbial communities successfully colonized the other environment and their degrading potential was kept. We then coupled biocidal treatments with serial dilutions to construct microbial community compositional variants in order to detect associations between specific bacterial OTUs and IPU and SMZ degrading capacities. Prediction models laid convincing results in predicting degradation rate and total degradation of communities from their composition. That for both xenobiotics, despite their differences in mineralisation dynamics ; IPU samples showing only few exponentially degrading communities and many non-degrading ones while SMZ samples are well dispersed concerning their degradation capacities.Upcoming work looks at community structure and co-occurrence networks, aiming at identifying groups and interactions -antagonist and cooperative- that play a role in the microbial degradation. From there, we could make enlightened choices for mixing wisely communities to obtain multi-degrading communities in a bioremediation perspective.