Assessment of agglomeration, co-sedimentation and trophic transfer of titanium dioxide nanoparticles in a laboratory-scale predator-prey model system

Govind Sharan Gupta,Alok Dhawan,Ashutosh Kumar,Rishi Shanker

doi:10.1038/srep31422

Abstract

Nano titanium dioxide (nTiO2) is the most abundantly released engineered nanomaterial (ENM) in aquatic environments. Therefore, it is prudent to assess its fate and its effects on lower trophic-level organisms in the aquatic food chain. A predator-and-prey-based laboratory microcosm was established using Paramecium caudatum and Escherichia coli to evaluate the effects of nTiO2. The surface interaction of nTiO2 with E. coli significantly increased after the addition of Paramecium into the microcosm. This interaction favoured the hetero-agglomeration and co-sedimentation of nTiO2. The extent of nTiO2 agglomeration under experimental conditions was as follows: combined E. coli and Paramecium > Paramecium only > E. coli only > without E. coli or Paramecium. An increase in nTiO2 internalisation in Paramecium cells was also observed in the presence or absence of E. coli cells. These interactions and nTiO2 internalisation in Paramecium cells induced statistically significant (p < 0.05) effects on growth and the bacterial ingestion rate at 24 h. These findings provide new insights into the fate of nTiO2 in the presence of bacterial-ciliate interactions in the aquatic environment.

Highlights

Nano titanium dioxide is the most abundantly released engineered nanomaterial (ENM) in aquatic environments
The trophic transfer of nTiO2 was further supported by the presence of packaged bacteria and nTiO2 in the egested Paramecium food vacuoles (SI-Fig. S10a). Bacterial abundance and their high surface-area-to-volume ratio increases the probability of interactions with ENMs in the environment
Bacteria are the simplest organisms in the lower trophic levels linked to ciliated protozoans in the upper trophic levels of the food chain

Summary

Introduction

Nano titanium dioxide (nTiO2) is the most abundantly released engineered nanomaterial (ENM) in aquatic environments. An increase in nTiO2 internalisation in Paramecium cells was observed in the presence or absence of E. coli cells These interactions and nTiO2 internalisation in Paramecium cells induced statistically significant (p < 0.05) effects on growth and the bacterial ingestion rate at 24 h. These findings provide new insights into the fate of nTiO2 in the presence of bacterial-ciliate interactions in the aquatic environment. The accumulation of ENMs can affect the growth, reproduction, ingestion and digestion behaviour of aquatic organisms[18,20,21] Factors such as surface interactions (adsorption or hetero-agglomeration), internalisation, oxidative stress, membrane damage and mitochondrial perturbations have been reported to be responsible for the acute toxicity of ENMs in microorganisms, cell lines www.nature.com/scientificreports/.

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