Impacts of Nanoplastics on the Viability and Riboflavin Secretion in the Model Bacteria Shewanella oneidensis

Abstract

Characterizing the impact of nanoplastics to organism health is important to understand the consequences of the environmental plastic waste problem. This article examines the impact of nano-polystyrene (nano-PS; 159 ± 0.9 nm diameter) to ecologically relevant bacteria Shewanella oneidensis. Bacterial viability was evaluated using a growth-based assay. Riboflavin secretion is a critical cell function of S. oneidensis, serving as an electron mediator in anaerobic respiration and/or as a signaling molecule when the bacteria are under stress. Thus, changes in cellular function were monitored through riboflavin secretion in order to evaluate toxic responses that may not result in cell death. Under aerobic and anaerobic exposures (4, 8, or 12 h), the viability of the S. oneidensis was minimally changed as compared to the control, while the concentration of riboflavin secreted varied with exposure dose. In order to determine if this was a specific response to nanoplastic particles, opposed to a response to either particles or plastic more generally, we exposed the system to colloidal TiO 2 nanoparticles and polystyrene and polyethylene thin films. We confirmed that riboflavin secretion trends were specific to nano-PS and not to these other materials, which showed no significant changes. We investigated the association of the nano-PS with ICP-MS using Pd that was chemically incorporated into the model nanoplastics. While 59.2% of the nano-PS were found in the non-cellular culture media, 7.0 and 6.6% was found associated with the loosely and tightly bound extracellular polymeric substance, respectively. There was significantly more nano-PS (10.9%) strongly associated with the cells. Taken together, we found that nano-PS had minimal impacts to viability but caused a significant change in the function of S. oneidensis that can be related to the nano-PS attached or in proximity to the bacterium. These trends are consistent between aerobic and anaerobic cultures, signifying that the stress response of S. oneidensis can be generalized between different environmental compartments. This work highlights that the association of nanoplastic materials with microorganisms may modify the cellular function that could ultimately be an impact to ecosystem health.

Metal-doping of nanoplastics enables accurate assessment of uptake and effects on Gammarus pulex

“…25 This approach has also been successfully applied to study the fate and behavior of NP in complex environmental systems 26,27 as well as the impacts to the model bacteria Shewanella oneidensis. 28 Aquatic organisms are able to actively ingest NP or adsorb them to their surfaces and transfer them into higher trophic levels. 8,18 The effects of NP on aquatic biota have raised particular concerns over the last years due to their small size, which allows them to be taken up by cells, affecting biota on a cellular level.…”

The analytical quest for sub-micron plastics in biological matrices

“…The use of 13 C-and 14 C-labeled SMPs can provide an effective way to establish whether the plastic is mineralized or whether it resists biodegradation. 14 C labeled SMPs have been used to investigate the uptake, biodistribution and depuration of SMPs in mollusks exposed to environmentally relevant concentrations (< 15 μg L -1 ) of SMPs [56]. This allowed for the application of radio-tracing tools, that are routinely used for chemicals, to 14 C labeled SMPs.…”

“…14 C labeled SMPs have been used to investigate the uptake, biodistribution and depuration of SMPs in mollusks exposed to environmentally relevant concentrations (< 15 μg L -1 ) of SMPs [56]. This allowed for the application of radio-tracing tools, that are routinely used for chemicals, to 14 C labeled SMPs. For instance, visualization of uptake and localization of 14 C labeled SMPs in biological matrices can be carried out using single-photon emission computed tomography, autoradiography, and positron emission tomography.…”

“…This allowed for the application of radio-tracing tools, that are routinely used for chemicals, to 14 C labeled SMPs. For instance, visualization of uptake and localization of 14 C labeled SMPs in biological matrices can be carried out using single-photon emission computed tomography, autoradiography, and positron emission tomography. Detection and quantification of 14 C labeled SMPs can be achieved using direct measurement of radio-carbon labeled SMPs using scintillation counters or measurement of the radio-carbon labeled CO 2 efflux upon SMP degradation, by means of wavelength-scanned cavity ring-down spectroscopy.…”

“…Recently, labeled or tagged SMPs were also investigated in various model environmental systems using metal-doped plastics as proxies in laboratory experiments using bench-top or pilot-scale systems [13]. Such approaches allow a novel perspective for tracking SMPs in organisms [14] and can advance understanding of how SMPs might behave as a function of their physicochemical properties in physiological media and how this correlates with their biological fate.…”