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Journal of Bacteriology, December 2008, p. 7994-8002, Vol. 190, No. 24
0021-9193/08/$08.00+0     doi:10.1128/JB.01039-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Moraxella catarrhalis M35 Is a General Porin That Is Important for Growth under Nutrient-Limiting Conditions and in the Nasopharynges of Mice{triangledown}

Donna M. Easton,1 Elke Maier,2 Roland Benz,2 A. Ruth Foxwell,1 Allan W. Cripps,1,3 and Jennelle M. Kyd1,4*

Faculty of Science, University of Canberra, Canberra, Australian Capital Territory 2601, Australia,1 Lehrstuhl für Biotechnologie, Theodor-Boveri-Institut (Biozentrum), Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany,2 School of Medicine, Griffith University, Gold Coast Campus, Gold Coast, Queensland 4222, Australia,3 Capricornia Centre for Mucosal Immunology, Central Queensland University, Rockhampton, Queensland 4702, Australia4

Received 28 July 2008/ Accepted 11 October 2008

Moraxella catarrhalis is a gram-negative respiratory pathogen that is an important causative agent for otitis media and exacerbations of chronic obstructive pulmonary disease. We have previously predicted the outer membrane protein M35 to be a general porin, and in the current study, we have investigated the function of M35 and its importance for survival of M. catarrhalis in vivo. Lipid bilayer experiments reveal that refolded M35 functions as a channel that is typical of gram-negative bacterial porins. M35 forms wide and water-filled channels with a single-channel conductance of about 1.25 nS in 1 M KCl solution and has only a small selectivity for cations over anions. When the in vitro growth characteristics of two M35 deletion mutant strains of M. catarrhalis were compared to the wild-type parent isolates, the growth of the mutant strains was inhibited only under nutrient-poor conditions. This growth defect could be eliminated by additional glutamic acid, but not additional aspartic acid, glycine, sucrose, or glucose. The mutant strains compensated for the lack of M35 by enhancing their uptake of glutamic acid, and this enhanced rate of glutamic acid uptake was attributed to the compensatory upregulation of a protein of approximately 40 kDa. M35 was also found to be essential for nasal colonization of mice, demonstrating that its presence is essential for survival of M. catarrhalis in vivo. These results suggest that M35 is a general porin that is necessary for the uptake of important energy sources by M. catarrhalis and that it is likely that M35 is an essential functional protein for in vivo colonization.

* Corresponding author. Mailing address: Faculty of Science, Engineering and Health, Central Queensland University, Bruce Highway, Rockhampton 4702, Queensland, Australia. Phone: 61 7 4930 6731 Fax: 61 7 4930 6415. E-mail: j.kyd{at}cqu.edu.au

{triangledown} Published ahead of print on 17 October 2008.

Journal of Bacteriology, December 2008, p. 7994-8002, Vol. 190, No. 24
0021-9193/08/$08.00+0     doi:10.1128/JB.01039-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • de Vries, S. P. W., Bootsma, H. J., Hays, J. P., Hermans, P. W. M. (2009). Molecular Aspects of Moraxella catarrhalis Pathogenesis. Microbiol. Mol. Biol. Rev. 73: 389-406 [Abstract] [Full Text]  
  • van der Hoeven, R., Forst, S. (2009). OpnS, an Outer Membrane Porin of Xenorhabdus nematophila, Confers a Competitive Advantage for Growth in the Insect Host. J. Bacteriol. 191: 5471-5479 [Abstract] [Full Text]  


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