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

¹ Department of Microbiology and Immunology, State University of New York at Buffalo, Buffalo, NY 14214, USA
² Witebsky Center for Microbial Pathogenesis and Immunology, State University of New York at Buffalo, Buffalo, NY 14214, USA
³ Division of Infectious Diseases, Department of Medicine, State University of New York at Buffalo, Buffalo, NY 14214, USA

Correspondence
Anthony A. Campagnari
aac{at}acsu.buffalo.edu

Moraxella catarrhalis is a leading cause of acute otitis media in children and is a cause of respiratory disease in adults with underlying lung disease. This organism is a strict human pathogen that has an absolute requirement for iron in order to grow and cause disease. Previous studies identified transferrin and lactoferrin receptors used by M. catarrhalis to obtain iron from the human host, yet other iron-acquisition systems remain undefined. In this study, it is demonstrated that this strict mucosal pathogen can utilize haemoglobin (Hb) as a sole source of iron for growth. A novel 107 kDa outer-membrane protein involved in Hb utilization by this pathogen was also identified. An isogenic mutant defective in this Moraxella Hb-utilization protein (MhuA), 7169 : : mhuA, showed a significant lag during growth in the presence of Hb as the sole iron source. This protein appears to be expressed constitutively, regardless of growth conditions, and a mAb directed to MhuA demonstrated that this protein contains highly conserved, surface-exposed epitopes. Data demonstrating that expression of MhuA may be highly specific to isolates of M. catarrhalis are also presented, suggesting a potential role as a diagnostic marker. To our knowledge, this is the first report demonstrating that M. catarrhalis expresses an Hb-binding protein and that this bacterium can utilize Hb as a sole iron source for growth.

The GenBank/EMBL/DDBJ accession number for the M. catarrhalis 7169 mhuA nucleic acid sequence and MhuA amino acid sequence reported in this paper is AY574198.

This article has been cited by other articles:

				P. Plamondon, N. R. Luke, and A. A. Campagnari Identification of a Novel Two-Partner Secretion Locus in Moraxella catarrhalis Infect. Immun., June 1, 2007; 75(6): 2929 - 2936. [Abstract] [Full Text] [PDF]