Alteration of Soil Bacteriome by Prolonged Exposure to Metal Oxide Nanoparticles

Metal oxide nanoparticles (MONPs) have found applications in many industrial and consumer products and are inevitably released into the environment, including soil. Soils host diverse microorganisms that are integral to ecosystem function including regulating plant growth. In this study, the influence of Cu2O, Fe3O4 and Ag2O NPs on soil microbial communities was assessed. Microbial community diversity and compositional structure was characterized using quantitative PCR and 16S rRNA gene sequencing. MONPs altered soil bacteria community composition by causing significant reduction in bacterial diversity and change in bacterial abundance. Soils with Cu2O and Ag2O NPs treatments significantly reduce bacterial diversity accompanied by shifts at the Class and Phylum taxonomic levels toward bacteria groups responsible for chitin degradation (Bacteriodetes) and nitrogen fixation (alpha-Proteobacteria). Response of bacterial communities to MONPs exposure is dependent on the exposure time and type of MONPs used. While the mechanisms underlying these observations remain to be elucidated, it is proposed that the known antimicrobial properties of Cu2O and Ag2O NPs cause reduced growth and viability of some bacteria taxa. ImportanceNanoparticles are finding many applications in society and as such there is the need to gain a better understanding of their potential effects on microorganisms in soil and other environmental niches. Soil contains a large diversity of microorganisms that play many essential roles in organic matter recycling and plant growth. Metagenomics has become an essential tool for understanding the functional diversity of microbiomes and in this study, it was used to assess the diversity of soil bacteria communities in the presence of selected metal oxide nanoparticles. The reported changes in bacterial community structure suggest that nanoparticles have the potential to alter soil microbiomes. However, the effects depend on the composition of the nanoparticles suggesting that environmental impacts of different nanoparticle formulations are necessary.