Nanomaterial Effects on Soil Microorganisms

Abstract

Nanomaterials like other types of industrial products may enter the environment through intentional and unintentional releases. It has been demonstrated using different methodologies, different indicators, and natural soils, which NMs could have an impact on microbial activities, abundances, and diversity. Effects on soil beneficial activities such as microbial N₂ cycle, symbiotic relations (e.g., AMF), Fe metabolism (siderophores), and production of antifungal compounds are particularly foreboding for microbial-dependent crop production. However, the toxic effects on microbial community are highly dependent on both the NMs considered and the soil properties. In fact, inorganic NMs (metal, metal oxide NPs) may have a greater toxic potential than organic NMs (fullerenes and CNTs) to soil microorganisms. The soil properties seem to play a key role for the bioavailability of NMs, especially the clay and organic matter content. Microbiologists strongly need to take more into consideration the physicochemical characteristics of the soil used in the experiments (texture, organic matter content, pH, etc.) and to compare the ecotoxicity of NMs in a range of different soils. The identification of soil parameters controlling the bioavailability of NMs is fundamental for a better environmental risk assessment. That being said, harnessing the full benefits of nanotechnology without degrading the ecosystem would require more studies conducted in real environmental conditions (soil) and continuous investigation into how less biotoxic NMs can be manufactured based on modifications on surface properties that would reduce the release of toxic ions or, possibly, tailoring the toxicity toward specific organisms, much like “narrow-spectrum” antibiotics. It is important to know that more attention is classically given to soil bacterial communities, despite the crucial role of fungal communities in energy flow and nutrient transfer in terrestrial ecosystems. New insights regarding the broad distribution and abundance of archaea in soils and oceans imply that they also contribute to global energy cycles, especially nitrogen cycle where ammonia-oxidizing archaea play a key role in nitrification. What is known on NM toxicity from in vitro studies using bacterial strains may not be extrapolated to archaeal and fungal communities. Thus, we must consider the response of archaeal and fungal communities to NM contamination, in order to have a better assessment of NM ecotoxicity in soils. For this, we need to collect an exhaustive data about microbial communities. Fortunately, modern tools and techniques have been developed in this field such as atomic force microscopy, metagenomics, and other molecular methods. They can help researchers to find more precise information comparing current tool and techniques.