title: Insight into the primary mode of action of TiO2 nanoparticles on Escherichia coli in the dark.
abstract: Large-scale production and incorporation of titanium dioxide nanoparticles (NP-TiO2 ) in consumer products leads to their potential release into the environment and raises the question of their toxicity. The bactericidal mechanism of NP-TiO2 under UV light is known to involve oxidative stress due to the generation of reactive oxygen species. In the dark, several studies revealed that NP-TiO2 can exert toxicological effects. However, the mode of action of these nanoparticles is still controversial. In the present study, we used a combination of fluorescent probes to show that NP-TiO2 causes Escherichia coli membrane depolarization and loss of integrity, leading to higher cell permeability. Using both transcriptomic and proteomic global approaches we showed that this phenomenon translates into a cellular response to osmotic stress, metabolism of cell envelope components and uptake/metabolism of endogenous and exogenous compounds. This primary mechanism of bacterial NP-TiO2 toxicity is supported by the observed massive cell leakage of K(+) /Mg(2+) concomitant with the entrance of extracellular Na(+), and by the depletion of intracellular ATP level.
authors.affiliation: Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC), UMR 7360, Université de Lorraine, Metz, France; CNRS, LIEC, UMR 7360, Metz, France.
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Sohm
authors.forename: Françoise
authors.initials: F
authors.lastname: Immel
authors.forename: Pascale
authors.initials: P
authors.lastname: Bauda
authors.forename: Christophe
authors.initials: C
authors.lastname: Pagnout
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D050296:Microbial Viability / Q000187:drug effects; D053758:Nanoparticles / Q000633:toxicity*; D009997:Osmotic Pressure / Q000187:drug effects; D010539:Permeability / Q000187:drug effects; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D014025:Titanium / Q000633:toxicity*; D059467:Transcriptome / Q000187:drug effects
chemical_list: D029968:Escherichia coli Proteins; C009495:titanium dioxide; D000255:Adenosine Triphosphate; D012964:Sodium; D014025:Titanium; D008274:Magnesium; D011188:Potassium
keywords: Escherichia coli; Microbiology; Osmotic stress; Titanium dioxide nanoparticles; Toxicity; Transcriptomics