Inhibitory effects of silver silicate (AgSiO₂) nanoparticles on uncultivable bacterial phyla present in soil

The transport of silver nanoparticles (AgNPs) into the soil occurs through various means by wastewater and other anthropogenic sources. The impact of silver silicate nanoparticle (AgSiO₂) application on the microbial community structure of rice field soil was evaluated. The results indicate that the introduction of AgSiO₂ alters the total bacterial community structure of the soil. Fascinatingly, the phylum WPS2 and Firmicutes showed lower abundance in nanoparticle-treated samples, which signifies their susceptibility to AgSiO₂ nanoparticles. The relative abundance of uncultivable phyla WPS2 was 8% in untreated soil, which was reduced to 0.09% by treatment of nanoparticles. However, there was no significant impact on the relative abundance of phyla Proteobacteria and Acidobacteria. Members of WPS2 have not been cultivated yet; therefore, information on their physiological and functional roles is not yet available. Functional analysis of the treated sample where WPS2 was abundant, had a higher representation of function related to bacterial motility proteins, nitrogen metabolism, carbon fixation, bacterial chemotaxis, oxidative phosphorylation, and photosynthesis proteins.