Journal of Bacteriology, September 2001, p. 5311-5316, Vol. 183, No. 18
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.18.5311-5316.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Departments of Pathology1 and Microbiology/Immunology,5 University of Arkansas for Medical Sciences, and Central Arkansas Veterans Healthcare System,2 Little Rock, Arkansas, and Medical Research Service, Department of Veterans Affairs Medical Center, Long Beach,3 and Department of Medicine, California College of Medicine, University of California, Irvine,4 California
Received 19 March 2001/Accepted 11 June 2001
Among the products that are expressed when Mycobacterium tuberculosis undergoes hypoxic shiftdown to nonreplicating persistence (NRP) is the alpha-crystallin chaperone protein homologue (Acr). This expression coincides with the previously reported appearance of a respiratory type of nitrate reductase activity, the increase in glycine dehydrogenase activity, and the production of a unique antigen, URB-1. In a timed sampling study, using a slowly stirred oxygen depletion culture model, we have demonstrated that the hspX mRNA that codes for Acr protein as well as the protein itself is induced just as the bacilli enter the microaerophilic NRP stage 1 (NRP-1). In contrast to the induction observed for hspX mRNA, levels of 16S rRNA, fbpB mRNA (encoding the 85B alpha antigen), and aroB mRNA (encoding dehydroquinate synthase) demonstrate relatively small to no change upon entering NRP-1. Acr protein was shown to be identical to URB-1 by Western analysis with anti-URB-1 antibody. The fact that antibody to Acr is found in a high percentage of tuberculosis patients suggests that the hypoxic shiftdown of tubercle bacilli to the NRP state that occurs in vitro, resulting in production of the alpha-crystallin protein, occurs in vivo as well. Simultaneous abrupt increases in hspX mRNA and Acr protein suggest that Acr protein expression is controlled at the level of transcription.
Present address: University of Iowa, Department of Medicine,
Division of Infectious Diseases and Veterans Affairs Medical Center,
Iowa City, IA 52246.
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