Effect of metal oxide nanoparticles on microbial community structure and function in two different soil types

Increased availability of nanoparticle-based products in the consumer market will, inevitably, expose the environment to these materials. Metallic oxide nanoparticles comprise one group of engineered nanoparticles (ENPs) with unique characteristics that are potentially hazardous for the environment. These materials may find their way to the soil environment via wastewater, dumpsters and other anthropogenic sources. Because the soil bacterial community is one of the major service providers for humankind, e.g., in terms of agricultural production, nutrient cycling and organic matter degradation, it is therefore 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 and a sandy clay loam. Results indicate that the sandy loam was more susceptible to change due to the exposure to these ENPs compared to the sandy clay loam. CuO had a strong effect on bacterial activity, community composition and size in the sandy loam. However, in the sandy clay loam, these effects were much mitigated or absent. Fe3O4 affected the activity and composition of the bacterial community only in the sandy loam. ENPs changed the bacterial diversity and richness of operational taxonomic units (OTUs) in both soils. The composition of the bacterial community was modified significantly, with distinct groups of gram positive bacteria (in particular Bacilli members) being specifically affected, both negatively and positively, according to the ENP type and concentration.