title: Capsule deletion via a λ-Red knockout system perturbs biofilm formation and fimbriae expression in Klebsiella pneumoniae MGH 78578.
abstract: BACKGROUND
  Klebsiella pneumoniae is a leading cause of hospital-acquired urinary tract infections and pneumonia worldwide, and is responsible for many cases of pyogenic liver abscess among diabetic patients in Asia. A defining characteristic of this pathogen is the presence of a thick, exterior capsule that has been reported to play a role in biofilm formation and to protect the organism from threats such antibiotics and host immune challenge.
  
  
  RESULTS
  We constructed two knockout mutants of K. pneumoniae to investigate how perturbations to capsule biosynthesis alter the cellular phenotype. In the first mutant, we deleted the entire gene cluster responsible for biosynthesis of the extracellular polysaccharide capsule. In the second mutant, we deleted the capsule export subsystem within this cluster. We find that both knockout mutants have lower amounts of capsule but produce greater amounts of biofilm. Moreover, one of the two mutants abolishes fimbriae expression as well.
  
  
  CONCLUSIONS
  These results are expected to provide insight into the interaction between capsule biosynthesis, biofilm formation, and fimbriae expression in this organism.
authors.forename: Tzu-Wen
authors.initials: TW
authors.lastname: Huang
authors.forename: Irene
authors.initials: I
authors.lastname: Lam
authors.forename: Hwan-You
authors.initials: HY
authors.lastname: Chang
authors.forename: Shih-Feng
authors.initials: SF
authors.lastname: Tsai
authors.forename: Bernhard O
authors.initials: BO
authors.lastname: Palsson
authors.affiliation: Department of Bioengineering, University of California, San Diego La Jolla, CA, 92093-0412 USA. pcharusanti@ucsd.edu.
authors.forename: Pep
authors.initials: P
authors.lastname: Charusanti
mesh_terms: D016667:Bacterial Capsules / Q000235:genetics / Q000502:physiology*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000502:physiology; D010582:Bacteriophage lambda / Q000201:enzymology; D018441:Biofilms / Q000254:growth & development; D001692:Biological Transport / Q000235:genetics; D010861:Fimbriae, Bacterial / Q000235:genetics*; D055786:Gene Knockout Techniques; D007711:Klebsiella pneumoniae / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D009876:Operon; D010641:Phenotype; D011135:Polysaccharides, Bacterial / Q000235:genetics / Q000378:metabolism; D012329:RNA, Bacterial / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D045522:Recombinases / Q000502:physiology; D059467:Transcriptome; D014764:Viral Proteins / Q000502:physiology; D014774:Virulence / Q000235:genetics; D047071:beta-Glucans / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D011135:Polysaccharides, Bacterial; D012329:RNA, Bacterial; D012333:RNA, Messenger; D045522:Recombinases; D014764:Viral Proteins; D047071:beta-Glucans; C505465:poly-N-acetyl-1-6-glucosamine