Novel sialic acid transporter of Haemophilus influenzae

Infect Immun. 2005 Sep;73(9):5291-300. doi: 10.1128/IAI.73.9.5291-5300.2005.


Nontypeable Haemophilus influenzae is an opportunistic pathogen and a common cause of otitis media in children and of chronic bronchitis and pneumonia in patients with chronic obstructive pulmonary disease. The lipooligosaccharides, a major component of the outer membrane of H. influenzae, play an important role in microbial virulence and pathogenicity. N-Acetylneuraminic acid (sialic acid) can be incorporated into the lipooligosaccharides as a terminal nonreducing sugar. Although much of the pathway of sialic acid incorporation into lipooligosaccharides is understood, the transporter responsible for N-acetylneuraminic acid uptake in H. influenzae has yet to be characterized. In this paper we demonstrate that this transporter is a novel sugar transporter of the tripartite ATP-independent periplasmic transporter family. In the absence of this transporter, H. influenzae cannot incorporate sialic acid into its lipooligosaccharides, making the organism unable to survive when exposed to human serum and causing reduced viability in biofilm growth.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Biofilms
  • Biological Transport
  • Electrophoresis, Polyacrylamide Gel
  • Haemophilus influenzae / genetics
  • Haemophilus influenzae / metabolism*
  • Lipopolysaccharides / metabolism
  • Molecular Sequence Data
  • N-Acetylneuraminic Acid / metabolism*
  • Organic Anion Transporters / genetics
  • Organic Anion Transporters / isolation & purification
  • Organic Anion Transporters / metabolism*
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Symporters / genetics
  • Symporters / isolation & purification
  • Symporters / metabolism*


  • Lipopolysaccharides
  • Organic Anion Transporters
  • Symporters
  • lipid-linked oligosaccharides
  • sialic acid transport proteins
  • N-Acetylneuraminic Acid

Associated data

  • GENBANK/DQ054469
  • GENBANK/DQ054470
  • GENBANK/DQ054471