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Journal of Bacteriology, March 2003, p. 1543-1554, Vol. 185, No. 5
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.5.1543-1554.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

A Two-Component Regulator of Universal Stress Protein Expression and Adaptation to Oxygen Starvation in Mycobacterium smegmatis

Ronan O'Toole, Marjan J. Smeulders, Marian C. Blokpoel, Emily J. Kay, Kathryn Lougheed, and Huw D. Williams*

Department of Biological Sciences, Imperial College London, London SW7 2AZ, United Kingdom

Received 9 August 2002/ Accepted 28 November 2002

We identified a response regulator in Mycobacterium smegmatis which plays an important role in adaptation to oxygen-starved stationary phase. The regulator exhibits strong sequence similarity to DevR/Rv3133c of M. tuberculosis. The structural gene is present on a multigene locus, which also encodes a sensor kinase. A devR mutant of M. smegmatis was adept at surviving growth arrest initiated by either carbon or nitrogen starvation. However, its culturability decreased several orders of magnitude below that of the wild type under oxygen-starved stationary-phase conditions. Two-dimensional gel analysis revealed that a number of oxygen starvation-inducible proteins were not expressed in the devR mutant. Three of these proteins are universal stress proteins, one of which is encoded directly upstream of devR. Another protein closely resembles a proposed nitroreductase, while a fifth protein corresponds to the {alpha}-crystallin (HspX) orthologue of M. smegmatis. None of the three universal stress proteins or nitroreductase, and a considerably lower amount of HspX was detected in carbon-starved wild-type cultures. A fusion of the hspX promoter to gfp demonstrated that DevR directs gene expression when M. smegmatis enters stationary phase brought about, in particular, by oxygen starvation. To our knowledge, this is the first time a role for a two-component response regulator in the control of universal stress protein expression has been shown. Notably, the devR mutant was 104-fold more sensitive than wild type to heat stress. We conclude that DevR is a stationary-phase regulator required for adaptation to oxygen starvation and resistance to heat stress in M. smegmatis.

* Corresponding author. Mailing address: Department of Biological Sciences, Imperial College London, Sir Alexander Fleming Bldg., Imperial College Road, London SW7 2AZ, United Kingdom. Phone: 44 (20) 75945383. Fax: 44 (20) 75842056. E-mail: h.d.williams{at}ic.ac.uk.

Journal of Bacteriology, March 2003, p. 1543-1554, Vol. 185, No. 5
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.5.1543-1554.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



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