Silver nanoparticles (AgNPs), found in over 50% of nanotechnology-integrated products including textiles, cosmetics, food packaging, and electronics, are a major anthropogenic stressor entering soils and disrupt essential microbial processes underpinning soil health. Therefore, it is crucial to investigate how and to what extent AgNPs affect soil health. However, only a few studies have focused on the potential effects of AgNPs on soil microbial communities.

In a study published in Environment International, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences explored how microbial functional gene approaches can be used to protect soil health against AgNPs. They proposed an approach to improve the accuracy of toxicity predictions and identify impaired soil processes by employing a functional genomics analysis.

As traditional approaches focusing on identifying microbial species (taxonomy) are insufficient due to the vast unculturable microbial diversity and high heterogeneity in toxicity responses, researchers suggested a paradigm shift towards analyzing microbial functional genes, focusing on the genetic blueprints for processes critical to soil health.

Researchers compiled comprehensive lists of AgNPs-tolerant and sensitive microbial taxa, which provides a crucial reference. They first examined ecotoxicological effects of AgNPs on the soil ecosystem, and then analyzed the tolerance thresholds of microbiomes as well as the most vulnerable ecosystem functions affected by AgNPs.

Specific functional genes involved in vital soil processes (e.g., nitrogen cycling, carbon decomposition) showed measurable, dose-dependent responses to AgNPs exposure. Monitoring these functional genes provided a more accurate and direct prediction of AgNPs' impact on actual soil functions and overall health than taxonomic surveys alone.

Researchers regarded that a functional genomics approach has significant advantages in predicting the impacts of AgNPs on soil microbial function and overall soil health. They proposed to establish soil-type-dependent toxicity thresholds using functional gene markers and to validate soil microbiome engineering approaches in field conditions.

"Protecting soil health from pervasive contaminants like AgNPs demands moving beyond simply counting microbes. Our functional gene-based framework is applicable for assessing and mitigating threats from other emerging soil contaminants," said YANG Xiaodong from XTBG.