title: Extracellular proteome of a highly invasive multidrug-resistant clinical strain of Acinetobacter baumannii.
abstract: The study of the extracellular proteomes of pathogenic bacteria is essential for gaining insights into the mechanisms of pathogenesis and for the identification of virulence factors. Through the use of different proteomic approaches, namely Nano-LC and 2DE combined with MALDI-TOF/TOF, we have characterized the extracellular proteome of a highly invasive, multidrug-resistant strain of A. baumannii (clone AbH12O-A2). This study focused on two main protein fractions of the extracellular proteome: proteins that are exported by outer membrane vesicles (OMVs) and freely soluble extracellular proteins (FSEPs) present in the culture medium of A. baumannii. Herein, a total of 179 nonredundant proteins were identified in the OMV protein fraction and a total of 148 nonredundant proteins were identified in FSEP fraction. Of the OMV proteins, 39 were associated with pathogenesis and virulence, including proteins associated with attachment to host cells (e.g., CsuE, CsuB, CsuA/B) and specialized secretion systems for delivery of virulence factors (e.g., P. pilus assembly and FilF), whereas the FSEP fraction possesses extracellular enzymes with degradative activity, such as alkaline metalloprotease. Furthermore, among the FSEP we have detected at least 18 proteins with a known role in oxidative stress response (e.g., catalase, thioredoxin, oxidoreductase, superoxide dismutase). Further assays demonstrated that in the presence of FSEPs, bacterial cells withstand much higher concentrations of H2O2 showing higher survival rate (approximately 2.5 fold) against macrophages. In this study we have identified an unprecedented number of novel extracellular proteins of A. baumannii and we provide insight into their potential role in relevant processes such as oxidative stress response and defense against macrophage attack.
authors.affiliation: Laboratório de Microbiología, Instituto de Investigación Biomédica de A Coruña (INIBIC), Servicio de Microbiología, Complejo Hospitalario Universitario A Coruña (CHUAC), As Xubias s/n, La Coruña, Spain.
authors.forename: Jose Antonio
authors.initials: JA
authors.lastname: Mendez
authors.forename: Nelson C
authors.initials: NC
authors.lastname: Soares
authors.forename: Jesús
authors.initials: J
authors.lastname: Mateos
authors.forename: Carmen
authors.initials: C
authors.lastname: Gayoso
authors.forename: Carlos
authors.initials: C
authors.lastname: Rumbo
authors.forename: Jesús
authors.initials: J
authors.lastname: Aranda
authors.forename: Maria
authors.initials: M
authors.lastname: Tomas
authors.forename: Germán
authors.initials: G
authors.lastname: Bou
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects / Q000201:enzymology* / Q000472:pathogenicity; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis*; D058947:Bacterial Secretion Systems; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000201:enzymology; D003470:Culture Media / Q000378:metabolism; D024901:Drug Resistance, Multiple, Bacterial; D015180:Electrophoresis, Gel, Two-Dimensional; D005110:Extracellular Space / Q000201:enzymology*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008264:Macrophages / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D050296:Microbial Viability; D018384:Oxidative Stress; D021381:Protein Transport; D020543:Proteome / Q000032:analysis*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D058947:Bacterial Secretion Systems; D003470:Culture Media; D020543:Proteome; D037521:Virulence Factors; D006861:Hydrogen Peroxide