Copper oxide nanoparticles slightly affect diversity and metabolic profiles of the prokaryotic community in pecan tree (Carya illinoinensis) rhizospheric soil

Abstract

The prokaryotic community in the pecan tree (Carya illinoinensis) rhizospheric soil with (clo) and without (non-clo) clover coverage exposed to copper oxide nanoparticles (CuO-NP) was evaluated by 16S rRNA amplicon sequencing. Treatments were applied with CuO-NP at concentrations of 0, 10, 100, and 1000 mg kg−1 soil and maintained for 45 days in microcosms. The analyses indicated that the prokaryotic microbial community of the soils consisted mainly of the phyla Thaumarchaeota, Proteobacteria, Actinobacteria, Bacteroidetes, Acidobacteria and Firmicutes (>80%). In terms of diversity, slight differences were observed between the control groups and their respective treatments and among treatments in both clo and non-clo soils. The community structure analyses showed the orders Caulobacterales, Burkholderiales, Xanthomonadales and Clostridiales significantly abundant (P < 0.05) at 1000 mg CuO-NP kg−1 soil. Their abundances coincide with the significant relevance of the ortholog groups (COG and KO) involved in metabolic pathways, such as, copper toxicity protection. The metabolic profile of the studied microbial communities is predominantly linked to nitrogen, sulfur, and halogen cycles. None of these metabolisms appeared to be drastically affected by CuO-NP. Hence, the findings in this study are encouraging as they imply that these nanoparticles may be used to deliver copper to copper-poor soils with subtle alteration of the soil microbiome metabolic capabilities.