Effect of TiO(2)-nanoparticles on copper toxicity to bacteria: role of bacterial surface

The impact of titanium dioxide nanoparticles (nano-TiO(2)) on the aquatic environment is an important issue due to their increasing application. Although nano-TiO(2) was reported to show an effect on heavy metal toxicity to aquatic organisms, the underlying mechanism is not well understood. In this study, two bacterial species (Bacillus thuringiensis (B. thuringiensis) and Bacillus megaterium (B. megaterium)) from sediment were selected to study the effects of nano-TiO(2) on copper toxicity. Nano-TiO(2) was found to inhibit the growth of B. thuringiensis and enhance the oxidative stress damage caused by copper, whereas these effects were not observed for B. megaterium. Transmission electron microscopy and flow cytometry showed that B. thuringiensis has stronger association ability to nano-TiO(2) than B. megaterium. The existence of the S-layer on the surface of B. thuringiensis might be the possible reason, leading to the difference in copper toxicity. This indicates that the characteristics of bacterial surfaces might be important to the toxicity responses of nanoparticles.