title: Ability of the marine bacterium Pseudomonas fluorescens BA3SM1 to counteract the toxicity of CdSe nanoparticles.
abstract: In the marine environment, bacteria from estuarine and coastal sediments are among the first targets of nanoparticle pollution; it is therefore relevant to improve the knowledge of interactions between bacteria and nanoparticles. In this work, the response of the marine bacterium Pseudomonas fluorescens BA3SM1 to CdSe nanocrystals (CdSe NPs) of 3nm (NP3) and 8nm (NP8) in diameter was evaluated through microscopic, physiological, biochemical and proteomic approaches. Transmission electron microscopy images showed that NP3 were able to penetrate the bacteria, while NP8 were highly concentrated around the cells, embedded in large exopolysaccharides. In our experimental conditions, both CdSe NP sizes induced a decrease in respiration during the stationary growth phase, while only NP8 caused growth retardation and a decrease in pyoverdine production. Proteomic analyses highlighted that the strain responded to CdSe NP toxicity by inducing various defence mechanisms such as cell aggregation, extracellular CdSe NP sequestration, effective protection against oxidative stress, modifications of envelope organization and properties, and cadmium export. In addition, BA3SM1 presented a biosorption capacity of 1.6×10(16)NP3/g dry weight and 1.7×10(15)NP8/g dry weight. This strain therefore appears as a promising agent for NP bioremediation processes. Proteomic data are available via ProteomeXchange with identifier PXD004012.
  
  
  
  To the best of our knowledge, this is the first report focussing on the effects of CdSe colloidal nanocrystals (CdSe NPs) on a marine strain of Pseudomonas fluorescens. CdSe NPs are extensively used in the industry of renewable energies and it is regrettably expected that these pollutants will sometime soon appear in the marine environment through surface runoff, urban effluents and rivers. Bacteria living in estuarine and coastal sediments will be among the first targets of these new pollutants. The pseudomonads are frequently found in these ecosystems. They are involved in several biogeochemical cycles and are known for their high resistance to pollutants. Consequently, this study focussing on the effects of CdSe NPs on the marine strain P. fluorescens BA3SM1 is highly relevant for several reasons. First, it aims at improving knowledge about the interactions between bacteria and NPs. This is fundamental to effectively use NPs against pathogenic bacteria. Secondly, in spite of CdSe NP interactions with the bacterial cells, the strain BA3SM1 can develop various strategies to counteract CdSe NP toxicity and ensure its growth. It exhibits interesting properties to sequester CdSe NPs and it retains its ability to form biofilm. The strain therefore appears as a promising agent for NP bioremediation thanks to biofiltration processes. Finally, this study shows that CdSe NPs of 8nm in diameter cause a decrease in the secretion of siderophore pyoverdine, a secondary metabolite playing a key role in microbial ecology since it drives bacterial survival and competitiveness in ecosystems. Bacteria producing effective siderophores survive better in a Fe-deficient environment where they antagonize the growth of other microbes thought iron deprivation. Furthermore, siderophores are also employed as virulence factors in human pathogenic strains such as P. aeruginosa. Consequently, this study highlights that NPs can impact the secondary metabolism of bacteria with environmental and medical implications. In addition, in this work, Data-Dependant Acquisition (DDA) provided state of the art Mass Spectrometry data by Spectral Counting and MS1 Label-Free. The combination of these two well-known proteomic techniques including manual validations strengthened the identification and quantification of regulated proteins. Moreover, numerous correlations between proteomic analyses and other observations (physiological, biochemical, microscopic) consolidated our interpretations.
authors: Institut National des Sciences et Techniques de la Mer, Conservatoire National des Arts et Métiers, 50103 Cherbourg-Octeville Cedex, France. Electronic address: isabelle.poirier@cnam.fr.
authors: Isabelle
authors: I
authors: Poirier
authors: Plateforme Protéomique Strasbourg Esplanade, CNRS FRC1589, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg Cedex, France.
authors: Lauriane
authors: L
authors: Kuhn
authors: Laboratoire de Réactivité et Chimie des Solides, CNRS UMR 7314, Université de Picardie Jules Verne, 80039 Amiens Cedex, France; Réseau sur le Stockage Electrochimique de l'Energie (RS2E), CNRS FR 3459, 80039 Amiens Cedex, France; Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, United States.
authors: Arnaud
authors: A
authors: Demortière
authors: Laboratoire de Réactivité et Chimie des Solides, CNRS UMR 7314, Université de Picardie Jules Verne, 80039 Amiens Cedex, France; Réseau sur le Stockage Electrochimique de l'Energie (RS2E), CNRS FR 3459, 80039 Amiens Cedex, France.
authors: Boris
authors: B
authors: Mirvaux
authors: Plateforme Protéomique Strasbourg Esplanade, CNRS FRC1589, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg Cedex, France.
authors: Philippe
authors: P
authors: Hammann
authors: Plateforme Protéomique Strasbourg Esplanade, CNRS FRC1589, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg Cedex, France.
authors: Johana
authors: J
authors: Chicher
authors: UMR BOREA, UCBN, MNHN, UPMC, CNRS-7208, IRD-207, Institut de Biologie Fondamentale et Appliquée, Normandie Université, 14032 Caen Cedex 5, France.
authors: Christelle
authors: C
authors: Caplat
authors: Institut National des Sciences et Techniques de la Mer, Conservatoire National des Arts et Métiers, 50103 Cherbourg-Octeville Cedex, France.
authors: Marie
authors: M
authors: Pallud
authors: Institut National des Sciences et Techniques de la Mer, Conservatoire National des Arts et Métiers, 50103 Cherbourg-Octeville Cedex, France.
authors: Martine
authors: M
authors: Bertrand
mesh_terms: D001673:Biodegradation, Environmental; D019187:Cadmium Compounds / Q000493:pharmacokinetics / Q000633:toxicity*; D017753:Ecosystem; D007220:Industrial Waste; D053768:Metal Nanoparticles / Q000737:chemistry; D010316:Particle Size; D040901:Proteomics; D011551:Pseudomonas fluorescens / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D018036:Selenium Compounds / Q000493:pharmacokinetics / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D019187:Cadmium Compounds; D007220:Industrial Waste; D018036:Selenium Compounds; D014874:Water Pollutants, Chemical; C058667:cadmium selenide
keywords: CdSe nanoparticles; Marine bacteria; Oxidative stress; Physiological responses; Proteomics