Bovine Serum Albumin Bends Over Backward to Interact with Aged Plastics: A Model for Understanding Protein Attachment to Plastic Debris.

Plastic pollution, a major environmental crisis, has a variety of consequences for various organisms within aquatic systems. Beyond the direct toxicity, plastic pollution has the potential to absorb biological toxins and invasive microbial species. To better understand the capability of environmental plastic debris to adsorb these species, we investigated the binding of the model protein bovine serum albumin (BSA) to polyethylene (PE) films at various stages of photodegradation. Circular dichroism and fluorescence studies revealed that BSA undergoes structural rearrangement to accommodate changes to the polymer's surface characteristics (i.e., crystallinity and oxidation state) that occur as the result of photodegradation. To understand how protein structure may inform docking of whole organisms, we studied biofilm formation of bacteriaShewanella oneidensison the photodegraded PE. Interestingly, biofilms preferentially formed on the photodegraded PE that correlated with the state of weathering that induced the most significant structural rearrangement of BSA. Taken together, our work suggests that there are optimal physical and chemical properties of photodegraded polymers that predict which plastic debris will carry biochemical or microbial hitchhikers.

The effect of plastic additives on Shewanella oneidensis growth and function.

Plastic waste has the potential for significant consequences on various ecosystems; yet, there are gaps in our understanding of the interaction of bacteria with polymer additives. We studied the impact of representative additive molecules to the viability and cell function of Shewanella oneidensis MR-1. Specifically, we explored the toxicity of three bisphenols (bisphenol A (BPA), bisphenol S (BPS), and tetrabromo bisphenol A (TBBPA)) and two diesters (dibutyl sebacate (DBS) and diisobutyl phthalate (DIBP)) in order to evaluate the generalizability of toxicity based on similar molecular structures. TBBPA caused significant, dose-dependent decreases in viability for acute (4 h) exposures in aerobic and anaerobic conditions. While the other 4 additives showed no significant toxicity upon 4 h exposures, chronic (2 day) anaerobic exposures revealed a significant impact to growth. BPA and BPS cause a significant decrease in growth rates for all exposure doses (8-131 µM) while DBS and DIBP had decreases in growth for the lowest exposure concentrations, though recovered to growth rates similar to the control at the highest concentrations. This highlights that S. oneidensis may have the ability to use the diesters as a carbon source if present in high enough concentrations. Riboflavin secretion was monitored as a marker of cellular health. Most additives stimulated riboflavin secretion as a survival response. Yet, there was no generalizable trend observed for these molecules, indicating the importance of considering the nuances of molecular structure to toxicity responses and the need for further work to understand the consequences of plastic waste in our environment.