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Infection and Immunity, June 2009, p. 2557-2567, Vol. 77, No. 6
0019-9567/09/$08.00+0 doi:10.1128/IAI.01481-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Department of Microbial and Molecular Pathogenesis, Texas A&M Health Sciences Center, 467 Reynolds Medical Building, College Station, Texas 77843 Howard Hughes Medical Institute, Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461
Received 3 December 2008/ Returned for modification 31 January 2009/ Accepted 28 March 2009
Persistence of Mycobacterium tuberculosis in humans represents a major roadblock to elimination of tuberculosis. We describe identification of a locus in M. tuberculosis, mel2, that displays similarity to bacterial bioluminescent loci and plays an important role during persistence in mice. We constructed a deletion of the mel2 locus and found that the mutant displays increased susceptibility to reactive oxygen species (ROS). Upon infection of mice by aerosol the mutant grows normally until the persistent stage, where it does not persist as well as wild type. Histopathological analyses show that infection with the mel2 mutant results in reduced pathology and both CFU and histopathology indicate that dissemination of the mel2 mutant to the spleen is delayed. These data along with growth in activated macrophages and infection of Phox–/– and iNOS–/– mice and bone marrow-derived macrophages suggest that the primary mechanism by which mel2 affects pathogenesis is through its ability to confer resistance to ROS. These studies provide the first insight into the mechanism of action for this novel class of genes that are related to bioluminescence genes. The role of mel2 in resistance to ROS is important for persistence and dissemination of M. tuberculosis and suggests that homologues in other bacterial species are likely to play a role in pathogenesis.
Published ahead of print on 6 April 2009.
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