Recent indications of nanoscale (<100 nm) metal oxide toxicity and their increased presence in the environment suggests that an understanding of that toxicity is urgently needed. We have conducted a suite of experiments exploring the levels and mechanisms of toxicity of a suite of metal oxide nanoparticles (ZnO, SnO2, and TiO2) on three model microorganisms: Escherichia coli, Staphylococcus aureus, and four strains of Pseudomonas aeruginosa (A+B+, A+B-, A-B+, and A-B-). Our data indicate each species has a unique level of resistance to metal oxide nanoparticles and that this resistance is due, in part, to electrostatic interactions at the cell surface, such that the presence of charged and uncharged o-oligosaacharides present in the lipopolysaccharide outermembrane (LPS) of gram negative cells influences NP toxicity to these organisms. Current studies are exploring the role of reactive oxygen species (ROS) and subsequent oxidative damage to cellular structures as a possible mechanism of toxicity for these particles. These studies provide evidence that these novel nanomaterials have the potential to be developed into valuable antimicrobials. Future studies by our group include targeted cell killing and induction of biofilm dispersion by active nanostructures.