Impact of Sublethal Levels of Single-Wall Carbon Nanotubes on Pyoverdine Production in <i>Pseudomonas aeruginosa</i> and Its Environmental Implications

Although bactericidal activities of nanomaterials against environmental bacteria have been extensively studied, little is known about the sublethal impacts of nanomaterials, which is a critical gap in our comprehensive understanding of the impacts of nanomaterials on microbial ecosystems. Using <i>Pseudomonas aeruginosa</i> as a model organism, we report for the first time that a sublethal level of single-wall carbon nanotubes (SWCNTs) (40 or 80 μg/mL) inhibited the production of pyoverdine, an important metabolite that is involved in interactive behavior of microbial communities. Transcriptional assay and quantitative polymerase chain reaction analysis revealed a decrease (up to 85%) in the level of expression of genes involved in biosynthesis and transport of pyoverdine in the presence of SWCNTs. Pyoverdine produced by certain bacteria in environmental microbial communities can be exploited by other bacteria in the local communities and has been implicated as playing an important role in establishing intercellular interactions. Our results of the inhibition of pyoverdine production in <i>P. aeruginosa</i> by SWCNTs at sublethal concentrations imply an important sublethal impact of SWCNTs on cell–cell interactions in microbial communities that often exist and play critical roles in maintaining the health of ecosystems in various natural and engineered environments