A MYCOBACTERIAL EXTRACYTOPLASMIC FUNCTION SIGMA-FACTOR INVOLVED IN SURVIVAL FOLLOWING STRESS

Citation
Ql. Wu et al., A MYCOBACTERIAL EXTRACYTOPLASMIC FUNCTION SIGMA-FACTOR INVOLVED IN SURVIVAL FOLLOWING STRESS, Journal of bacteriology, 179(9), 1997, pp. 2922-2929
Citations number
40
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
ISSN journal
0021-9193
Volume
179
Issue
9
Year of publication
1997
Pages
2922 - 2929
Database
ISI
SICI code
0021-9193(1997)179:9<2922:AMEFSI>2.0.ZU;2-6
Abstract
The extracytoplasmic function (ECF) sigma factors constitute a diverse group of alternative sigma factors that have been demonstrated to reg ulate gene expression in response to environmental conditions in sever al bacterial species. Genes encoding an ECF sigma factor of Mycobacter ium tuberculosis, Mycobacterium avium, and Mycobacterium smegmatis, de signated sigE, were cloned and analyzed. Southern blot analysis demons trated the presence of a single copy of this gene in these species and in Mycobacterium bovis BCG, Mycobacterium leprae, and Mycobacterium f ortuitum. Sequence analysis showed the sigE gene to be highly conserve d among M. tuberculosis, M. avium, M. smegmatis, and M. leprae. Recomb inant M. tuberculosis SigE, when combined with core RNA polymerase fro m M. smegmatis, reconstituted specific RNA polymerase activity on sigE in vitro, demonstrating that this gene encodes a functional sigma fac tor, Two in vivo transcription start sites for sigE were also identifi ed in M. smegmatis and M. bovis BCG. Comparison of wild-type M. smegma tis with a sigE mutant strain demonstrated decreased survival of the m utant under conditions of high-temperature heat shock, acidic pH, expo sure to detergent, and oxidative stress, An inducible protective respo nse to oxidative stress present in the wild type was absent in the mut ant, The mycobacterial SigE protein, although nonessential for viabili ty in vitro,appears to play a role in the ability of these organisms t o withstand a variety of stresses,