Effect of Metal Oxide Nanoparticles on Microbial Community Structure and Function in Two Different Soil Types

Sammy Frenk,Tal Ben-Moshe,Dror Minz,Ishai Dror,Brian Berkowitz,Leonard Simon Van Overbeek

doi:10.1371/journal.pone.0084441

Sammy Frenk, Tal Ben-Moshe + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0084441

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Abstract

Increased availability of nanoparticle-based products will, inevitably, expose the environment to these materials. Engineered nanoparticles (ENPs) may thus find their way into the soil environment via wastewater, dumpsters and other anthropogenic sources; metallic oxide nanoparticles comprise one group of ENPs that could potentially be hazardous for the environment. Because the soil bacterial community is a major service provider for the ecosystem and humankind, it is critical to study the effects of ENP exposure on soil bacteria. These effects were evaluated by measuring bacterial community activity, composition and size following exposure to copper oxide (CuO) and magnetite (Fe3O4) nanosized (<50 nm) particles. Two different soil types were examined: a sandy loam (Bet-Dagan) and a sandy clay loam (Yatir), under two ENP concentrations (1%, 0.1%). Results indicate that the bacterial community in Bet-Dagan soil was more susceptible to change due to exposure to these ENPs, relative to Yatir soil. More specifically, CuO had a strong effect on bacterial hydrolytic activity, oxidative potential, community composition and size in Bet-Dagan soil. Few effects were noted in the Yatir soil, although 1% CuO exposure did cause a significant decreased oxidative potential and changes to community composition. Fe3O4 changed the hydrolytic activity and bacterial community composition in Bet-Dagan soil but did not affect the Yatir soil bacterial community. Furthermore, in Bet-Dagan soil, abundance of bacteria annotated to OTUs from the Bacilli class decreased after addition of 0.1% CuO but increased with 1% CuO, while in Yatir soil their abundance was reduced with 1% CuO. Other important soil bacterial groups, including Rhizobiales and Sphingobacteriaceae, were negatively affected by CuO addition to soil. These results indicate that both ENPs are potentially harmful to soil environments. Furthermore, it is suggested that the clay fraction and organic matter in different soils interact with the ENPs and reduce their toxicity.

Highlights

Materials at the nanometer scale are not new, having been reported to be found naturally in various environments, including volcanic dust [1], oceans [2], fresh water [3] and soils [4,5]
We explored the effect of concentration of these MO-engineered nanoparticles (ENPs) by comparing two different contaminant doses, 0.1% and 1% w/w
The soil microbial communities in the two soil types showed a general trend of decrease in dehydrogenase oxidative potential (DEH) and hydrolytic activities (FDA) following exposure to CuO (Figure 1a and 1b)

Summary

Introduction

Materials at the nanometer scale are not new, having been reported to be found naturally in various environments, including volcanic dust [1], oceans [2], fresh water [3] and soils [4,5]. Anthropogenic engineered nanoparticles (ENPs) have appeared relatively recently, with their manufacturing and use becoming widespread only during the last decade [6]. ENPs are often designed to be extremely reactive, and they have characteristics, unlike some of their natural counterparts, that may be harmful to different life forms including microorganisms and animals. The presence of anthropogenic ENPs in the environment, TiO2, has already been reported in streams [8] and wastewater treatment plants [10]. The increase of new ENP-based products promises a steady increase in ENP production, availability and discharge to the environment [11]

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