TiO ₂ Photocatalysis Damages Lipids and Proteins in Escherichia coli

Abstract

e This study investigates the mechanisms of UV-A (315 to 400 nm) photocatalysis with titanium dioxide (TiO 2 ) applied to the degradation of Escherichia coli and their effects on two key cellular components: lipids and proteins. The impact of TiO 2 photocatalysis on E. coli survival was monitored by counting on agar plate and by assessing lipid peroxidation and performing proteomic analysis. We observed through malondialdehyde quantification that lipid peroxidation occurred during the photocatalytic process, and the addition of superoxide dismutase, which acts as a scavenger of the superoxide anion radical (O 2 · ؊ ), inhibited this effect by half, showing us that O 2 · ؊ radicals participate in the photocatalytic antimicrobial effect. Qualitative analysis using twodimensional electrophoresis allowed selection of proteins for which spot modifications were observed during the applied treatments. Two-dimensional electrophoresis highlighted that among the selected protein spots, 7 and 19 spots had already disappeared in the dark in the presence of 0.1 g/liter and 0.4 g/liter TiO 2 , respectively, which is accounted for by the cytotoxic effect of TiO 2 . Exposure to 30 min of UV-A radiation in the presence of 0.1 g/liter and 0.4 g/liter TiO 2 increased the numbers of missing spots to 14 and 22, respectively. The proteins affected by photocatalytic oxidation were strongly heterogeneous in terms of location and functional category. We identified several porins, proteins implicated in stress response, in transport, and in bacterial metabolism. This study reveals the simultaneous effects of O 2 · ؊ on lipid peroxidation and on the proteome during photocatalytic treatment and therefore contributes to a better understanding of molecular mechanisms in antibacterial photocatalytic treatment.

Systematic Approach to In-Depth Understanding of Photoelectrocatalytic Bacterial Inactivation Mechanisms by Tracking the Decomposed Building Blocks

“…The decrease of protein concentration occurred very earlier in the PEC process, and the cytoplasmic protein leakage seems unlikely responsible, especially in the first 15 min considering a membrane did not permeabilize significantly until 15 min; so the loss of membrane associated proteins may occur at this stage. 43 Another reason may be that aggregation of proteins after PEC makes protein insoluble for extraction. 44 In contrast, the protein concentration reduction was not observed during the PC or EC processes, consistent with their poor bactericidal performance.…”

Unveiling the photoelectrocatalytic inactivation mechanism of Escherichia coli : Convincing evidence from responses of parent and anti-oxidation single gene knockout mutants

“…potential is important for transporting various substrate across the membrane (Bosshard et al, 2010). Besides the functional disruption of the bacterial membrane, structural damage like lipid peroxidation caused by the ROSs attack may be responsible for the increased membrane permeability (Carre et al, 2014). Compared with the mutants, BW25113 showed slower K þ leakage.…”

Bactericidal efficiency of UV-active TiO2 thin films on adhesion and viability of food-borne bacteria

“…(Gupta et al, 2013;Wang et al, 2015). Such properties were also observed on adherent cells (Carré et al, 2014;Chorianopoulos et al, 2011). This leads to many applications including medical devices that are far described in the literature.…”