(584e) Potential Impact of Sublethal Levels of Nanomaterials on Interactive Behavior of Environmental Bacteria

Although bactericidal effects of a wide range of nanomaterials on environmental bacteria have been extensively reported, little is known about the impact of nanomaterials at sublethal levels on environmental bacteria and their interactive behaviors, which is a critical gap toward a comprehensive understanding of the impacts of nanomaterials on microbial ecosystems. In this study, using model environmental bacteria, we report the impact of single-wall carbon nanotubes (SWCNTs) and nanoSilver (nAg) on cell-to-cell interaction through influencing the production of â??public goodsâ? or the production of quorum sensing (QS) signals. Sublethal level of SWCNTs (40 or 80 µg/ml) inhibited the production of pyoverdine (PVD) (an important metabolite that involves in interactive behavior of microbial communities, especially in iron-limiting environments) in planktonic cultures of Pseudomonas aeruginosa. The inhibitory effect has been confirmed at the mRNA level by transcriptional assay and quantitative polymerase chain reaction (qPCR) analysis. We further explored the effect of SWCNTs on mature biofilms of P. aeruginosa. Our results showed that the exposure to SWCNTs for up to 48 h did not significantly influence PVD production in cells encased in mature biofilms; however, the exposure to SWCNTs promoted cell detachment from the biofilms and decreased PVD production of the detached cells. To explore the influence of nanomaterials on quorum sensing, we used P. syringae and Pantoea stewartii as model organisms and quantified the influence of SWCNTs and nAg on the production of different acylated homoserine lactones (AHL) signals. Our results showed for the first time that differential effects could be exhibited by nanomaterials on different QS signals. Our findings advance current knowledge toward a comprehensive understanding of the ecotoxicity of nanomaterials.