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Novel sialic acid transporter of Haemophilus influenzae

Simon Allen1, Anthony Zaleski, Jason W Johnston

  • 1Buck Institute for Age Research, 8001 Redwood Blvd., Novato, California 94945, USA.

Infection and Immunity
|August 23, 2005
PubMed

Insights

Researchers identified a novel transporter crucial for N-acetylneuraminic acid uptake in Nontypeable Haemophilus influenzae. This transporter is essential for incorporating sialic acid into lipooligosaccharides, impacting bacterial survival in human serum and biofilms.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Nontypeable Haemophilus influenzae (NTHi) is an opportunistic pathogen causing significant respiratory infections and otitis media.
  • Lipooligosaccharides (LOS) on the NTHi outer membrane are key virulence factors.
  • N-Acetylneuraminic acid (sialic acid) incorporation into LOS is a known virulence mechanism, but the uptake transporter remains uncharacterized.

Purpose of the Study:

  • To identify and characterize the transporter responsible for N-acetylneuraminic acid uptake in NTHi.
  • To elucidate the role of this transporter in NTHi virulence and survival.

Main Methods:

  • Genetic analysis and mutant construction of NTHi.
  • Functional assays to assess sialic acid incorporation into LOS.
  • Phenotypic characterization of NTHi mutants under serum exposure and biofilm growth conditions.

Main Results:

  • A novel sugar transporter belonging to the tripartite ATP-independent periplasmic transporter family was identified as the N-acetylneuraminic acid transporter.
  • NTHi strains lacking this transporter were unable to incorporate sialic acid into their LOS.
  • The absence of the transporter rendered NTHi non-viable in human serum and significantly reduced biofilm viability.

Conclusions:

  • The characterized transporter is essential for N-acetylneuraminic acid uptake and subsequent LOS modification in NTHi.
  • This transporter plays a critical role in NTHi virulence, mediating resistance to host immune defenses (serum) and contributing to biofilm formation.

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