Cu-doped TiO2 nanoparticles enhance survival of Shewanella oneidensis MR-1 under Ultraviolet Light (UV) exposure

It has been shown that photocatalytic TiO2 nanoparticles (NPs) can be used as an efficient anti-microbial agent under UV light due to generation of reactive oxygen species (ROS), while Shewanella oneidensis MR-1 is a metal-reducing bacterium highly susceptible to UV radiation. Interestingly, we found that the presence of Cu-doped TiO2 NPs in the cultural medium dramatically increased the survival rates (based on colony-forming unit) of strain MR-1 by over 10,000-fold (incubation without shaking) and ~ 200 fold (incubation with shaking) after a 2-h exposure to UV light. Gene expression results (via qPCR measurement) indicated that the DNA repair gene recA in MR-1 was significantly induced by UV exposure (indicating cellular damage under UV stress), but the influence of NPs on recA expression was not statistically evident. Plausible explanations to NP attenuation of UV stresses are: 1. TiO2 based NPs are capable of scattering and absorbing UV light and thus create a shading effect to protect MR-1 from UV radiation; 2. more importantly, Cu-doped TiO2 NPs can co-agglomerate with MR-1 to form large flocs that improves cells' survival against the environmental stresses. This study improves our understanding of NP ecological impacts under natural solar radiation and provides useful insights to application of photocatalytic-NPs for bacterial disinfection.

► Survival of Shewanella oneidensis MR-1 under UV exposure is significantly improved in the presence of photocatalytic-NPs.
► Co-agglomeration of NPs with MR-1 cells can protect MR-1 against UV stress.
► NPs can also absorb harmful light to reduce cell damages.