A stationary-phase stress-response sigma factor from Mycobacterium tuberculosis

James Demaio, Ying Zhang, Chiew Ko, Douglas B. Young, William R. Bishai

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156 Scopus citations


Alternative RNA polymerase sigma factors are a common means of coordinating gene regulation in bacteria. Using PCR amplification with degenerate primers, we identified and tinned a sigma factor gene, sigF, from Mycobacterium tuberculosis. The deduced protein encoded by sigF shows significant similarity to SigF sporulation sigma factors from Streptomyces coelicolor and Bacillus subtilis and to SigB, a stress-response sigma factor, from B. subtilis. Southern blot surveys with a sigF-specific probe identified cross-hybridizing bands in other slow-growing mycobacteria, Mycobacterium bovis bacille Calmette-Guerin (BCG) and Mycobacterium avium, but nut in the rapid-growers Mycobacterium smegmatis or Mycobacterium abscessus. RNase protection assays revealed that M. tuberculosis sigF mRNA is not present during exponential-phase growth in M. bovis BCG cultures but is strongly induced during stationary phase, nitrogen depletion, and cold shuck. Weak expression of M. tuberculosis sigF was also detected during late-exponential phase, oxidative stress, anaerobiasis, and alcohol shock. The specific expression of M. tuberculosis sigF during stress or stationary phase suggests that it may play a role in the ability of tubercle bacilli to adapt to host defenses and persist during human infection.

Original languageEnglish (US)
Pages (from-to)2790-2794
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number7
StatePublished - Apr 2 1996

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