The impact of various forms of silver nanoparticles on the rhizosphere of wheat (Triticum aestivum L.) - Shifts in microbiome structure and predicted microbial metabolic functions

Abstract

The study investigated the effects of different silver nanoparticles (AgNPs) on the soil microbiome and wheat growth. For comparison purposes, a commercial fungicide and silver nitrate (AgNO₃) were used. The results revealed three distinct groups of nanoparticles based on their impacts. Small-size AgNPs (10 nm) with a negative charge, as well as fungicide had limited effects on the microbiome, similar to the no-treatment control. Bigger in size (30-60 nm) and a negative charge AgNPs showed the most beneficial effects on soil microbiota shifts. These AgNPs increased the abundance of bacteria with beneficial traits such as nitrogen-fixing, urease, protease, and lignin degradation bacteria. The third type of AgNPs had a positive charge of nanostructure and influenced specific microbial populations, increasing the abundance of anaerobic and autotrophic groups of microorganisms, which could be assessed as a harmful shift for plants growth promotions and was similar to the AgNO₃ treatment. Overall, the study emphasized the potential of AgNPs in agriculture not only as biocidal. The conducted study proved that AgNPs with bigger size/negative charge, used in low concentration can have a surprisingly stimulating effect on the positive characteristics of the rhizosphere microbiome. Moreover, the surface charge of AgNPs is a significant factor affecting microbial activity of wheat rhizosphere soil, which in this treatment is significantly similar to the AgNO₃ treatment.

Keywords: Metabolic functions; Microbiomes; Network analysis; PGPR; Rhizosphere.