Visualizing Microbial Communities on Plastic Marine Debris: Identification, Interactions and Impacts

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Plastic marine debris (PMD) is an increasing anthropogenic pollutant in the global ocean. The effects on marine animals due to entanglement or ingesting have been reported, however, the effect of PMD on microorganisms, such as bacteria, archaea or protists that form the base of the food web, is poorly known. Due to the special properties of PMD, it can serve as a new habitat for certain microbes and seems to be able to transport even harmful microbes over long distances and distribute them in foreign marine regimes. Moreover, PMD enables microbes to live for a long time in close proximity, which might influence the pathways of different chemical compounds. To understand the impact of PMD associated microbes on marine environments, we need to identify the composition and interactions of the microbial communities on PMD and how they are globally distributed. I will characterize the diversity and the spatial distribution of microbial communities residing on PMD already collected from biogeographically diverse marine regions (Atlantic, Pacific, Indian Ocean, Mediterranean and Caribbean Sea). I aim to: 1) identify which microbes are occurring on PMD; 2) investigate the spatial structure of the microbial communities residing on PMD and bio-based plastics; 3) examine which microbes are most closely associated with the plastic polymer surface; 4) investigate if there are core microbiomes on PMD characteristic for different oceanic regions; and, 5) examine which microbes can degrade PMD in environmental samples and in incubation experiments using natural assemblages and microbes already identified as putative hydrocarbon degraders. The chances of obtaining successful outcomes from this project are high, because samples are already available on which to apply an innovative microscopy technique called CLASIFISH (Combinatorial Labelling and Spectral Imaging Fluorescence In Situ Hybridization). This technique enables fast and precise identification of hundreds of different microbial taxa, and their spatial distribution, on a single piece of PMD. CLASI-FISH was developed at my host institution, and my host, Prof. Dr. Amaral-Zettler will train me to design appropriate phylogenetic probes and conduct classical FISH experiments, as well as CLASI-FISH experiments. When I am proficient with the methods, I will apply them to different samples collected in the Atlantic and Pacific Ocean and to natural samples containing potential degraders of PMD that have yet to be identified. Additionally, I will conduct incubation experiments with Plastisphere bacterial cultures maintained in my host laboratory. These experiments will include investigations of how microbial assemblages develop over time on bio-based plastics, and if/how these microbes degrade plastic. During these incubation experiments, I will apply FISH and CLASIFISH methods, as well as scanning electron microscopy, metagenomics and metatranscriptomic approaches, as feasible.