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Identification of a conserved Moraxella catarrhalis haemoglobin-utilization protein, MhuA

Kristin Furano1,2, Nicole R Luke1,2, Amy J Howlett1,2

  • 1Witebsky Center for Microbial Pathogenesis and Immunology, State University of New York at Buffalo, Buffalo, NY 14214, USA.

Microbiology (Reading, England)
|April 9, 2005
PubMed

Insights

Moraxella catarrhalis, a pathogen causing ear and lung infections, can use hemoglobin (Hb) as its sole iron source. A novel Hb-utilization protein (MhuA) was identified, crucial for this iron acquisition.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Iron Metabolism

Background:

  • Moraxella catarrhalis is a significant human pathogen responsible for acute otitis media in children and respiratory infections in adults.
  • Iron is essential for M. catarrhalis growth and virulence, with known acquisition mechanisms involving transferrin and lactoferrin.
  • Other iron acquisition systems in M. catarrhalis remain incompletely understood.

Purpose of the Study:

  • To investigate the ability of Moraxella catarrhalis to utilize hemoglobin (Hb) as an iron source.
  • To identify and characterize novel proteins involved in Hb utilization by M. catarrhalis.
  • To assess the potential of identified proteins as diagnostic markers.

Main Methods:

  • Growth assays using hemoglobin as the sole iron source.
  • Construction and analysis of an isogenic mutant (7169::mhuA) lacking the Moraxella Hb-utilization protein (MhuA).
  • Characterization of MhuA expression and surface epitopes using monoclonal antibodies (mAbs).

Main Results:

  • Moraxella catarrhalis can grow using hemoglobin as its sole iron source.
  • A novel 107 kDa outer-membrane protein, MhuA, was identified as essential for Hb utilization.
  • The mhuA mutant exhibited a significant growth lag in the presence of Hb as the sole iron source.
  • MhuA is constitutively expressed and possesses conserved, surface-exposed epitopes.
  • MhuA expression appears specific to M. catarrhalis isolates, suggesting diagnostic potential.

Conclusions:

  • Moraxella catarrhalis possesses a novel system for iron acquisition via hemoglobin utilization, mediated by the MhuA outer-membrane protein.
  • MhuA is a surface-exposed protein critical for bacterial growth on hemoglobin.
  • MhuA represents a potential species-specific diagnostic marker for Moraxella catarrhalis infections.

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