Unveiling marine plastic degraders through DNA-stable isotope probing

Plastic biodegradation in natural environments is performed by the microbial biofilm living on its surface. This study identifies for the first time plastic degraders in marine environment, by using stable isotope tracers. Polyhydroxybutyrate (PHB) biodegradation was proved by monitoring microbial cell growth (via scanning electron microscopy and flow cytometry) and activities (via continuous oxygen consumption measurements and ³H-leucine incorporation for protein synthesis) during 90 days. We successfully synthetized ¹³C-labeled PHB and conducted DNA-stable isotope probing (DNA-SIP) experiments over different time points, which permitted the first description of key PHB degraders belonging to Marinobacter sp. and Cellvibrionaceae together with Glaciecola sp., Pseudoalteromonas sp., Celeribacter sp. and Alteromonas sp. Overall, SIP labeling combined with metabarcoding proved to be a useful tool for discovering and characterizing active plastic degraders from complex marine communities.