As the nanotechnology industry grows, so will the concentration of synthetic nanoparticles in the environment as a result of manufacturing processes, industrial waste, and consumer waste. Titanium dioxide nanoparticles (nano-TiO2) are widely produced and are already found in a range of mainstream products. When released into the environment (either intentionally or otherwise), available nano-TiO2 will interact with bacteria in virtually every environmental niche. However, little is known about these interactions and how nano-TiO2 may affect bacterial processes. A better understanding of these interactions could offer insight into both potential toxicity and fate of nano-TiO2 in the environment. This research presents initial findings on the toxicity of nano-TiO2 to planktonic Pseudomonas putida, an environmentally widespread and metabolically versatile soil bacterium. Toxicity of nano-TiO2 in both light and dark conditions was studied by quantifying bacterial growth characteristics (lag time, growth rate, and cell yield) over a range of nano-TiO2 concentrations. Under dark conditions, we observed a significant decrease in cell yield and growth rate with increasing nano-TiO2 concentrations, indicating a dose-response effect. Non-nanoparticulate TiO2 in the presence of UV-light has been widely shown to cause toxicity via oxidative stress, but the dark conditions with nano-TiO2 studied were not expected to cause similarly toxic effects. Metal association with cells is quantified by ICP-MS in order to better describe cell binding and nano-TiO2 fate. Environmental scanning electron microscopy (ESEM) is used to observe effects of nano-TiO2 on cell morphology as well as metal associations with cells. A complete understanding of nano-TiO2-bacterial interactions with regards to fate and toxicity may have implications for nanoparticle waste management and decontamination strategies in the future.