title: Growth of Acinetobacter baumannii in pellicle enhanced the expression of potential virulence factors.
abstract: BACKGROUND
  Interestingly, Acinetobacter baumannii presents an enhanced capacity to form biofilms (also named pellicles) at the air-liquid interface as compared to the other Acinetobacter species. This characteristic questions the contribution of this phenotype to an increased risk of clinical infections by this pathogen.
  
  
  RESULTS
  By a proteomic approach using 2-D gel electrophoresis-LC-MS/MS mass spectrometry, we compared the membrane protein patterns of A. baumannii 77, a pellicle-forming clinical isolate, grown in planktonic and in sessile modes. We identified 52 proteins with a differential expression, including 32 up-regulated and 20 down-regulated in the pellicle state. Several proteins, differentially expressed during pellicle development, were of particular interest. We determined the over-expression of four siderophore iron uptake systems including the acinetobactin and enterobactin receptors and confirmed that the development of this type of biofilm is promoted by ferric ions. Two over-expressed proteins, CarO and an OprD-homologue, putative carbapenem-resistance associated porins, would be involved in the transport of specific compounds, like ornithine, a biosynthesis precursor of a siderophore from the hydroxamate family. We evidenced the overexpression of a lipase and a transporter of LCFA that may be involved in the recycling of lipids inside the pellicle matrix. Finally, we demonstrated both by proteomic and by AFM studies that this particular type of biofilm required multiple pili systems to maintain this cohesive structure at the air-liquid interface; two of these systems have never been described in A. baumannii.
  
  
  CONCLUSIONS
  Our study demonstrated that several proteins, overexpressed at a late state of pellicle development, could be potentially involved in virulence processes. Therefore, regarding the number of potential virulence factors that are over-expressed in this growth mode, the pellicle-forming clinical isolates should be kept under survey.
authors: Laboratoire Polymères Biopolymères Surfaces, UMR 6270 & FR 3038 CNRS, University of Rouen, Mont Saint Aignan, France.
authors: Sara
authors: S
authors: Marti
authors: Yassine
authors: Y
authors: Nait Chabane
authors: Stéphane
authors: S
authors: Alexandre
authors: Laurent
authors: L
authors: Coquet
authors: Jordi
authors: J
authors: Vila
authors: Thierry
authors: T
authors: Jouenne
authors: Emmanuelle
authors: E
authors: Dé
mesh_terms: D040981:Acinetobacter baumannii / Q000254:growth & development*; D001426:Bacterial Proteins / Q000032:analysis*; D018441:Biofilms / Q000254:growth & development; D044622:Dental Pellicle / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008565:Membrane Proteins / Q000032:analysis; D040901:Proteomics / Q000379:methods; D037521:Virulence Factors / Q000032:analysis / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D037521:Virulence Factors