title: Chemical analysis of cellular and extracellular carbohydrates of a biofilm-forming strain Pseudomonas aeruginosa PA14.
abstract: BACKGROUND
  Pseudomonas aeruginosa is a gram-negative bacterium and an opportunistic pathogen, which causes persisting life-threatening infections in cystic fibrosis (CF) patients. Biofilm mode of growth facilitates its survival in a variety of environments. Most P. aeruginosa isolates, including the non-mucoid laboratory strain PA14, are able to form a thick pellicle, which results in a surface-associated biofilm at the air-liquid (A-L) interface in standing liquid cultures. Exopolysaccharides (EPS) are considered as key components in the formation of this biofilm pellicle. In the non-mucoid P. aeruginosa strain PA14, the "scaffolding" polysaccharides of the biofilm matrix, and the molecules responsible for the structural integrity of rigid A-L biofilm have not been identified. Moreover, the role of LPS in this process is unclear, and the chemical structure of the LPS O-antigen of PA14 has not yet been elucidated.
  
  
  RESULTS
  In the present work we carried out a systematic analysis of cellular and extracellular (EC) carbohydrates of P. aeruginosa PA14. We also elucidated the chemical structure of the LPS O-antigen by chemical methods and 2-D NMR spectroscopy. Our results showed that it is composed of linear trisaccharide repeating units, identical to those described for P. aeruginosa Lanýi type O:2a,c (Lanýi-Bergman O-serogroup 10a, 10c; IATS serotype 19) and having the following structure: -4)-α-L-GalNAcA-(1-3)-α-D-QuiNAc-(1-3)- α-L-Rha-(1-. Furthermore, an EC O-antigen polysaccharide (EC O-PS) and the glycerol-phosphorylated cyclic β-(1,3)-glucans were identified in the culture supernatant of PA14, grown statically in minimal medium. Finally, the extracellular matrix of the thick biofilm formed at the A-L interface contained, in addition to eDNA, important quantities (at least ∼20% of dry weight) of LPS-like material.
  
  
  CONCLUSIONS
  We characterized the chemical structure of the LPS O-antigen and showed that the O-antigen polysaccharide is an abundant extracellular carbohydrate of PA14. We present evidence that LPS-like material is found as a component of a biofilm matrix of P. aeruginosa.
authors.affiliation: Université Lille Nord de France, Lille, France.
authors.forename: Charlène
authors.initials: C
authors.lastname: Coulon
authors.forename: Evgeny
authors.initials: E
authors.lastname: Vinogradov
authors.forename: Alain
authors.initials: A
authors.lastname: Filloux
authors.forename: Irina
authors.initials: I
authors.lastname: Sadovskaya
mesh_terms: D018441:Biofilms; D002241:Carbohydrates / Q000737:chemistry*; D004587:Electrophoresis, Agar Gel; D005227:Fatty Acids / Q000737:chemistry; D008070:Lipopolysaccharides / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D019081:O Antigens / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation; D011108:Polymers / Q000737:chemistry; D011134:Polysaccharides / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000378:metabolism*
chemical_list: D002241:Carbohydrates; D005227:Fatty Acids; D008070:Lipopolysaccharides; D019081:O Antigens; D011108:Polymers; D011134:Polysaccharides