Effects of Various Carbon Nanotubes on Soil Bacterial Community Composition and Structure

Carbon nanotubes (CNTs) have huge industrial potential, and their environmental impacts need to be evaluated. Knowledge of CNT impacts on soil microbial communities is still limited. To address this knowledge gap, we systematically examined dynamic effects of one type of single-walled carbon nanotubes (SWs) and three multiwalled carbon nanotubes (MWs) with different outer diameters on the soil bacterial community in an agricultural soil over 56 days. The results showed that SWs differently affected soil bacterial abundance, diversity, and composition as compared to MWs. The differences could have resulted from the materials' distinct physical structure and surface composition, which in turn affected their bioavailability in soil. For certain treatments, soil bacterial diversity and the relative abundance of certain predominant phyla were correlated with their exposure duration. However, many phyla recovered to their initial relative abundance within 56 days, reflecting resilience of the soil bacterial community in response to CNT-induced disturbance. Further analysis at the genus level showed differential tolerance to MWs, as well as size- and dose-dependent tolerance among bacterial genera. Predictive functional profiling showed that while CNTs initially caused fluctuations in microbial community function, community function largely converged across all treatments by the end of the 56 day exposure.