Journal of Bacteriology, April 2001, p. 2316-2321, Vol. 183, No. 7
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.7.2316-2321.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
B
Department of Microbiology, MC 7758, University of Texas Health Science Center, San Antonio, Texas 78229-3900
Received 16 October 2000/Accepted 19 January 2001
B, the general stress response sigma factor of
Bacillus subtilis, is activated when the cell's energy
levels decline or the bacterium is exposed to environmental stress
(e.g., heat shock, ethanol). Physical stress activates
B
through a collection of regulatory kinases and phosphatases (the Rsb
proteins) which catalyze the release of
B from an
anti-
B factor inhibitor. The means by which diverse
stresses communicate with the Rsb proteins is unknown; however, a role
for the ribosome in this process was suggested when several of the
upstream members of the
B stress activation cascade
(RsbR, -S, and -T) were found to cofractionate with ribosomes in crude
B. subtilis extracts. We now present evidence for the
involvement of a ribosome-mediated process in the stress activation of
B. B. subtilis strains resistant to the
antibiotic thiostrepton, due to the loss of ribosomal protein L11
(RplK), were found to be blocked in the stress activation of
B. Neither the energy-responsive activation of
B nor stress-dependent chaperone gene induction (a
B-independent stress response) was inhibited by the loss
of L11. The Rsb proteins required for stress activation of
B are shown to be active in the RplK
strain but fail to be triggered by stress. The data demonstrate that
the B. subtilis ribosomes provide an essential input for the stress activation of
B and suggest that the
ribosomes may themselves be the sensors for stress in this system.
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