Abstract
Marine plastic pollution is a global problem of increasing magnitude. Plastics accumulate in ocean subtropical gyres, zones of convergence and coastal systems, but little is known about the ultimate fate of plastics in the marine realm. Only a small fraction of all plastic that has ever been released into the ocean can be accounted for. Abiotic and biotic factors mediate plastic degradation, but so far, only a few microorganisms have been found capable of degrading specific plastic polymers. One group of microorganisms that is generally understudied is marine fungi, although fungi are often involved in the breakdown of very complex and recalcitrant organic matter. I successfully isolated several fungal species from marine plastic debris collected from the North Atlantic and Pacific Oceans. In pilot experiments with Rhodotorula mucilaginosa and 13C isotopically-labelled polyethylene, I determined fungal-mediated plastic conversion into CO2 and traced 13C-label from the polymer into single microbial cells via nanoSIMS measurements. Additional experiments indicated that other fungal species might be able to degrade several plastic types. Based on these findings, I hypothesize that marine fungi are important plastic degraders. With this proposal, I plan to (i) determine the identity of fungal communities on plastic polymers from a variety of contrasting ocean environments through 18S rRNA and ITS gene amplicon sequencing; (ii) isolate and cultivate fungal strains with plastic polymers as the sole carbon source; (iii) investigate fungal-mediated plastic degradation rates and the fate of plastic-derived carbon using stable isotope assays; (iv) identify genomic traits and enzymes involved in plastic degradation to determine the metabolic potential of marine fungi to break down the plastic polymers. This project will expand our knowledge on microbially-mediated degradation of marine plastic and broaden our view on marine fungi.
Netherlands