Taxonomic and functional diversity of bacterial communities of agriculture soil exposed to zinc peroxide nanoparticles (nZnO2)

Abstract

Zinc peroxide nanoparticles (nZnO2) have interesting physicochemical properties for multiple industrial applications. Due to their wide use, their direct or indirect release and accumulation in soil represent a potential risk for microbial communities, among others. However, no reports have been found on their potential ecological risks in their soil-fate environment. Thus, this study evaluates the effect of nZnO2 on taxonomic and functional diversity of bacterial communities (BC) of agriculture soil. For this purpose, the soil was exposed to three concentrations of nZnO2 (10, 100 and 1000 mg/kg of soil) in microcosms that were evaluated after 15 and 30 days. The taxonomic and functional diversity of the BC was determined using amplicon sequencing (16S rRNA), physiological profiles (CLPP) and enzymatic activity. Exposure to low concentrations of nZnO2 (up to 100 mg/kg soil) on days 15 and 30 led to an increase of taxonomic diversity, while at 1000 mg/kg nZnO2, taxonomic and functional diversity were reduced in both exposure times. At day 30 (1000 mg/kg nZnO2), a significant impact on taxonomic diversity was manifested by (i) reduction in relative abundance of approximately 40 taxonomic groups, mainly from Rhizobiales, Azospirillales (Pseudomonadota, synonym: Proteobacteria) and increase in relative abundance of Lachnospirales (Bacillota, synonym: Firmicutes), Bacteroidales (Bacteroidota, synomym: Bacteroidetes) and others; (ii) reduction in metabolism of amino acids and amines/amides; and (iii) increase in dehydrogenase and urease activities with respect to the controls. These findings may indicate that the accumulation of large concentrations of nZnO2 in soil would negatively affect the soil biological functions, due to changes in the taxonomic and functional diversity of its BC, whereas low concentrations would likely promote them.