Abstract
SummaryDecades after incorporating plastics into consumer markets, research shows that these polymers have spread worldwide. Fragmentation of large debris leads to smaller particles, collectively called microplastics (MPs), which have become ubiquitous in aquatic environments. A fundamental aspect of understanding the implications of MP contamination on ecosystems is resolving the complex interactions of these artificial substrates with microbial cells. Using polystyrene microparticles as model polymers, we conducted an exploratory study where these interactions are quantitatively analyzed using an in vitro system consisting of single‐bacterial species capturing and aggregating MPs in water. Here we show that the production of Psl exopolysaccharide by Pseudomonas aeruginosa (PA) does not alter MPs colloidal stability but plays a key role in microspheres adhesion to the cell surface. Further aggregation of MPs by PA cells depends on bacterial mobility and the presence of sufficient flow to prevent rapid sedimentation of early MP‐PA assembles. Surprisingly, cells in MP‐PA aggregates are not in a sessile state despite the production of Psl, enhancing the motility of the aggregates by an order of magnitude relative to passive diffusion. The generated data could inform the creation of predictive models that accurately describe the dynamics and influence of bacterial growth on plastics debris.
Highlights
The extensive use and inadequate disposal of plastics in modern life, combined with the long persistence of these synthetic polymers in the environment, has resulted in plastic debris being recognized as a serious threat to human health and ecosystems (Kvale et al, 2021; Rahman et al, 2021)
To explore the process of MPs capture by microorganisms in aquatic environments, green fluorescent PS microspheres were exposed to different bacterial species (Table 1) in a laboratory-based study. 0.5 μm diameter microspheres were chosen as model MPs since their small dimensions render inertia negligible and Cobetia marina Phaeobacter gallaeciensis Pseudomonas aeruginosa Pseudomonas sp
The ‘Aggregation time’ column indicates times when clumping was first noticed in the microbe/MPs mixtures and in brackets the time difference when cellular aggregation was visible in vials with bacteria only
Summary
The extensive use and inadequate disposal of plastics in modern life, combined with the long persistence of these synthetic polymers in the environment, has resulted in plastic debris being recognized as a serious threat to human health and ecosystems (Kvale et al, 2021; Rahman et al, 2021). The transport of MPs in the water systems will be strongly influenced by its modified buoyancy due to association with microorganisms, with important implications on the distribution of MPs (Long et al, 2015; Kooi et al, 2017). Another potential outcome of MPs accumulation in microbial biofilms is plastic degradation, as MPs could be surrounded by other organic matter and enzymes that may accelerate chemical and physical plastic dissolving processes.
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