title: A crucial role for exopolysaccharide modification in bacterial biofilm formation, immune evasion, and virulence.
abstract: Biofilms play an important role in many chronic bacterial infections. Production of an extracellular mixture of sugar polymers called exopolysaccharide is characteristic and critical for biofilm formation. However, there is limited information about the mechanisms involved in the biosynthesis and modification of exopolysaccharide components and how these processes influence bacterial pathogenesis. Staphylococcus epidermidis is an important human pathogen that frequently causes persistent infections by biofilm formation on indwelling medical devices. It produces a poly-N-acetylglucosamine molecule that emerges as an exopolysaccharide component of many bacterial pathogens. Using a novel method based on size exclusion chromatography-mass spectrometry, we demonstrate that the surface-attached protein IcaB is responsible for deacetylation of the poly-N-acetylglucosamine molecule. Most likely due to the loss of its cationic character, non-deacetylated poly-acetylglucosamine in an isogenic icaB mutant strain was devoid of the ability to attach to the bacterial cell surface. Importantly, deacetylation of the polymer was essential for key virulence mechanisms of S. epidermidis, namely biofilm formation, colonization, and resistance to neutrophil phagocytosis and human antibacterial peptides. Furthermore, persistence of the icaB mutant strain was significantly impaired in a murine model of device-related infection. This is the first study to describe a mechanism of exopolysaccharide modification that is indispensable for the development of biofilm-associated human disease. Notably, this general virulence mechanism is likely similar for other pathogenic bacteria and constitutes an excellent target for therapeutic maneuvers aimed at combating biofilm-associated infection.
authors.affiliation: Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, NIAID, National Institutes of Health, Hamilton, Montana 59840, USA.
authors.forename: Cuong
authors.initials: C
authors.lastname: Vuong
authors.forename: Stanislava
authors.initials: S
authors.lastname: Kocianova
authors.forename: Jovanka M
authors.initials: JM
authors.lastname: Voyich
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Yao
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Fischer
authors.forename: Frank R
authors.initials: FR
authors.lastname: DeLeo
authors.forename: Michael
authors.initials: M
authors.lastname: Otto
mesh_terms: D000107:Acetylation; D000117:Acetylglucosamine / Q000032:analysis / Q000096:biosynthesis / Q000502:physiology; D000581:Amidohydrolases / Q000235:genetics / Q000502:physiology; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D018441:Biofilms; D002850:Chromatography, Gel; D004864:Equipment and Supplies / Q000382:microbiology; D013058:Mass Spectrometry; D051379:Mice; D009154:Mutation; D009504:Neutrophils / Q000276:immunology; D010587:Phagocytosis; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D013203:Staphylococcal Infections / Q000382:microbiology; D013212:Staphylococcus epidermidis / Q000276:immunology / Q000472:pathogenicity* / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial; C113831:poly-N-acetyl glucosamine; D000581:Amidohydrolases; C497363:poly-N-acetylglucosamine deacetylase; D000117:Acetylglucosamine