title: Zinc oxide induces the stringent response and major reorientations in the central metabolism of Bacillus subtilis.
abstract: Microorganisms, such as bacteria, are one of the first targets of nanoparticles in the environment. In this study, we tested the effect of two nanoparticles, ZnO and TiO2, with the salt ZnSO4 as the control, on the Gram-positive bacterium Bacillus subtilis by 2D gel electrophoresis-based proteomics. Despite a significant effect on viability (LD50), TiO2 NPs had no detectable effect on the proteomic pattern, while ZnO NPs and ZnSO4 significantly modified B. subtilis metabolism. These results allowed us to conclude that the effects of ZnO observed in this work were mainly attributable to Zn dissolution in the culture media. Proteomic analysis highlighted twelve modulated proteins related to central metabolism: MetE and MccB (cysteine metabolism), OdhA, AspB, IolD, AnsB, PdhB and YtsJ (Krebs cycle) and XylA, YqjI, Drm and Tal (pentose phosphate pathway). Biochemical assays, such as free sulfhydryl, CoA-SH and malate dehydrogenase assays corroborated the observed central metabolism reorientation and showed that Zn stress induced oxidative stress, probably as a consequence of thiol chelation stress by Zn ions. The other patterns affected by ZnO and ZnSO4 were the stringent response and the general stress response. Nine proteins involved in or controlled by the stringent response showed a modified expression profile in the presence of ZnO NPs or ZnSO4: YwaC, SigH, YtxH, YtzB, TufA, RplJ, RpsB, PdhB and Mbl. An increase in the ppGpp concentration confirmed the involvement of the stringent response during a Zn stress. All these metabolic reorientations in response to Zn stress were probably the result of complex regulatory mechanisms including at least the stringent response via YwaC.
authors.affiliation: Pro-MD team, Université Joseph Fourier, CEA Grenoble, iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR CNRS-CEA-UJF, Grenoble, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Luche
authors.affiliation: Pro-MD team, Université Joseph Fourier, CEA Grenoble, iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR CNRS-CEA-UJF, Grenoble, France.
authors.forename: Elise
authors.initials: E
authors.lastname: Eymard-Vernain
authors.affiliation: Laboratoire de Spectrométrie de Masse Bio-Organique, IPHC, Université de Strasbourg, 25 rue Becquerel, 67087 Strasbourg, France; CNRS, UMR7178, 67087 Strasbourg, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Diemer
authors.affiliation: Laboratoire de Spectrométrie de Masse Bio-Organique, IPHC, Université de Strasbourg, 25 rue Becquerel, 67087 Strasbourg, France; CNRS, UMR7178, 67087 Strasbourg, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Van Dorsselaer
authors.affiliation: Pro-MD team, UMR CNRS 5249, Laboratoire de Chimie et Biologie des Métaux, UMR CNRS-CEA-UJF, Grenoble, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Rabilloud
authors.affiliation: Pro-MD team, Université Joseph Fourier, CEA Grenoble, iRTSV, Laboratoire de Chimie et Biologie des Métaux, UMR CNRS-CEA-UJF, Grenoble, France. Electronic address: cecile.lelong@ujf-grenoble.fr.
authors.forename: Cécile
authors.initials: C
authors.lastname: Lelong
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D013312:Stress, Physiological / Q000187:drug effects*; D015034:Zinc Oxide / Q000494:pharmacology*
chemical_list: D001426:Bacterial Proteins; D015034:Zinc Oxide