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Infection and Immunity, October 2006, p. 5477-5486, Vol. 74, No. 10
0019-9567/06/$08.00+0     doi:10.1128/IAI.00798-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

The mgtC Gene of Burkholderia cenocepacia Is Required for Growth under Magnesium Limitation Conditions and Intracellular Survival in Macrophages

Kendra E. Maloney1 and Miguel A. Valvano1,2*

Infectious Diseases Research Group, Siebens-Drake Research Institute, Departments of Microbiology and Immunology,1 Medicine, University of Western Ontario, London, Ontario, N6A 5C1, Canada2

Received 17 May 2006/ Returned for modification 27 June 2006/ Accepted 7 July 2006

Burkholderia cenocepacia, a bacterium commonly found in the environment, is an important opportunistic pathogen in patients with cystic fibrosis (CF). Very little is known about the mechanisms by which B. cenocepacia causes disease, but chronic infection of the airways in CF patients may be associated, at least in part, with the ability of this bacterium to survive within epithelial cells and macrophages. Survival in macrophages occurs in a membrane-bound compartment that is distinct from the lysosome, suggesting that B. cenocepacia prevents phagolysosomal fusion. In a previous study, we employed signature-tagged mutagenesis and an agar bead model of chronic pulmonary infection in rats to identify B. cenocepacia genes that are required for bacterial survival in vivo. One of the most significantly attenuated mutants had an insertion in the mgtC gene. Here, we show that mgtC is also needed for growth of B. cenocepacia in magnesium-depleted medium and for bacterial survival within murine macrophages. Using fluorescence microscopy, we demonstrated that B. cenocepacia mgtC mutants, unlike the parental isolate, colocalize with the fluorescent acidotropic probe LysoTracker Red. At 4 h postinfection, mgtC mutants expressing monomeric red fluorescent protein cannot retain this protein within the bacterial cytoplasm. Together, these results demonstrate that, unlike the parental strain, an mgtC mutant does not induce a delay in phagolysosomal fusion and the bacterium-containing vacuoles are rapidly targeted to the lysosome, where bacteria are destroyed.

* Corresponding author. Mailing address: Infectious Diseases Research Group, Siebens-Drake Research Institute, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, N6A 5C1, Canada. Phone: (519) 661-3996. Fax: (519) 661-3499. E-mail: mvalvano{at}uwo.ca.

Editor: J. N. Weiser

Infection and Immunity, October 2006, p. 5477-5486, Vol. 74, No. 10
0019-9567/06/$08.00+0     doi:10.1128/IAI.00798-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



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