Boris Eyheraguibel

Every year, rivers introduce a staggering amount of hundred kilotons of plastic into the Oceans. This plastic is inhabited by microorganisms known as the plastisphere, which can be transferred between different ecosystems through the transport of microplastics. Here, we simulated the microbial colonization of polyethylene-based plastic pellets that are classically used to manufacture large-scale plastic products. The pellets were immersed for 1 month in four to five sampling stations along the river-to-sea continuum of nine of the major European rivers. This study presents the first untargeted metabolomics analysis of the plastisphere, by using ultra high-performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS). The plastisphere metabolomes were similar in the Rhine and Rhone rivers, while being different from the Tiber and Loire rivers, which showed greater similarity to the Thames and Seine rivers. Interestingly, we found a clear distinction between plastisphere metabolomes from freshwater and marine water in most of the river-to-sea continuum, thus suggesting a complete segregation in plastisphere metabolites that is not consistent with a major transfer of microorganisms between the two contrasted ecosystems. Putative annotations of 189 discriminating metabolites suggested that lipid metabolism was significantly modulated. These results enlightened the relevance of using environmental metabolomic as complementary analysis to the current OMICs analysis. Graphical Abstract

The occurrence of micro and nano plastics has been reported in every environmental compartment including marine and freshwaters, soils and sediments, air and atmospheric precipitations. Recent evidence showing the presence of airborne microplastics in remote ecosystems highlights the extent of this pollution. The atmospheric transportation and the distribution of airborne microplastics still need to be better documented to understand the dynamic of microplastic transfer between ecosystems.While most studies dedicated to the analysis of microplastics in the air use a passive sampling methodology through atmospheric deposition we developed an original stainless device to sample large volumes of air with high debit (2000 L/min) providing a fast sampling of aerosols within a small localized area. An optimized sampling protocol has been deployed in the North Western Mediterranean Sea from the Expedition 7th Continent (E7C) boat. 19 sampling sites have been studied during the E7C expedition in September-October 2019, including measurements in port and coastal areas as well as offshore environments. The analysis of micro/nano plastics was carried out using pyrolysis coupled with gas chromatography and tandem mass spectrometry (Py-GC-MS/MS). This approach allowed us to evaluate the concentrations of micro and nano plastics present in the samples for 5 types of plastics (polypropylene, polystyrene, polymethyl methacrylate, polyethylene terephthalate and polycarbonate) and for 2 size ranges (5-50μm and <5μm).This study confirmed that plastic particles are present in the atmosphere even in remote areas such as the offshore environments. The results showed that airborne micro and nano plastics were detected at each sampling station, from the coast to the open sea, at various concentrations. Py-GC-MS/MS analysis allowed us to quantify the 5 types of polymer and revealed the predominance of PET and PP material. High-volume samplers and Py-GC-MS/MS analysis have proven to be an efficient and powerful methodology to gather and quantify airborne plastic particles at micro and nanoscale level.

Plastics are associated with a worldwide pollution crisis, with strong negative impacts on both terrestrial and aquatic ecosystems. In marine environments, various organisms are colonizing plastic debris, but few studies have focused on fungal communities despite their non-trivial ecological roles in the marine environment. In this study, different types of plastics (biodegradable and conventional) immersed in marine natural environments and under laboratory controlled settings were collected after long-term colonization. Using a metabarcoding approach targeting two genetic markers, namely, the ITS2 region and the V4 hypervariable region of the 18S rRNA gene, we highlighted that fungal communities associated with plastic polymers were distinct from those found in the surrounding seawater. They also differed significantly between sampling locations and the nature of immersed polymers, indicating that fungal colonization was impacted by the sites and types of plastics, with clear dissimilarities between conventional and biodegradable polymers. Specifically for the conventional PVC polymer (Polyvinyl chloride), we also observed the successive stages of biofilm development and maturation after long-term immersion in seawater. A noticeable change in the fungal communities was observed around 30–40 days in natural settings, suggesting a colonization dynamic likely associated with a transition from biofilm formation to distinct communities likely associated with biofouling. Overall, this study strengthens the idea that the fungal kingdom is an integrated part of the “plastisphere”.

A new scientific hypothesis states that biosurfactants from cloud microorganism origin could change the surface tension of aerosols and thus the mode of precipitations. In order to check this hypothesis, our team has screened a collection of 480 microbial strains isolated from cloud waters for the production of biosurfactants and showed that 42% of these strains were producing such molecules. In the present work, we isolated and identified by LC-MS-MS lipopeptides produced from three strains issued from this screening. Viscosin and massetolide E (cyclic lipopeptides) were produced by Pseudomonas sp. PDD-14b-2, and syringafactins (linear lipopeptides) were produced by Xanthomonas campestris PDD-32b-52 and Pseudomonas syringae PDD-32b-74. The critical micelle concentration (CMC) of these biosurfactants was determined using the pendant drop method. Finally, two approaches of molecular dynamics were used to model the conformation of viscosin and syringafactin A at the water-air interface: one is based on all-atoms simulation (CHARMM force field), while the other one on coarse-grain (CG) simulation (MARTINI force field). To conclude, this work shows how the biodiversity of the cloud microbiota can be explored to search and produce biosurfactants of interest both for atmospheric sciences and also for biotechnological applications.

Plastics are ubiquitous in the oceans and constitute suitable matrices for bacterial attachment and growth. Understanding biofouling mechanisms is a key issue to assessing the ecological impacts and fate of plastics in marine environment. In this study, we investigated the different steps of plastic colonization of polyolefin-based plastics, on the first one hand, including conventional low-density polyethylene (PE), additivated PE with pro-oxidant (OXO), and artificially aged OXO (AA-OXO); and of a polyester, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), on the other hand. We combined measurements of physical surface properties of polymers (hydrophobicity and roughness) with microbiological characterization of the biofilm (cell counts, taxonomic composition, and heterotrophic activity) using a wide range of techniques, with some of them used for the first time on plastics. Our experimental setup using aquariums with natural circulating seawater during 6 weeks allowed us to characterize the successive phases of primo-colonization, growing, and maturation of the biofilms. We highlighted different trends between polymer types with distinct surface properties and composition, the biodegradable AA-OXO and PHBV presenting higher colonization by active and specific bacteria compared to non-biodegradable polymers (PE and OXO). Succession of bacterial population occurred during the three colonization phases, with hydrocarbonoclastic bacteria being highly abundant on all plastic types. This study brings original data that provide new insights on the colonization of non-biodegradable and biodegradable polymers by marine microorganisms.

The whole genome of Rhodococcus enclensis 23b-28, a bacterial strain isolated from cloud water, was sequenced. This microorganism is equipped with genes able to degrade aromatic compounds and could thus play a role in complex organic matter decomposition in cloud water.