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J. Bacteriol., Jun 1996, 3113-3118, Vol 178, No. 11
T Caramori, D Barilla, C Nessi, L Sacchi and A Galizzi
The alternative sigma factor sigma D directs transcription of a number of
genes involved in chemotaxis, motility, and autolysis in Bacillus subtilis
(sigmaD regulon). The activity of SigD is probably in contrast to that of
FlgM, which acts as an antisigma factor and is responsible for the coupling
of late flagellar gene expression to the assembly of the hook-basal body
complex. We have characterized the effects of an in- frame deletion
mutation of flgM. By transcriptional fusions to lacZ, we have shown that in
FlgM-depleted strains there is a 10-fold increase in transcription from
three different sigmaD-dependent promoters, i.e., Phag, PmotAB, and
PfliDST. The number of flagellar filaments was only slightly increased by
the flgM mutation. Overexpression of FlgM from a multicopy plasmid under
control of the isopropyl-beta-D- thiogalactopyranoside-inducible spac
promoter drastically reduced the level of transcription from the hag
promoter. On the basis of these results, we conclude that, as in Salmonella
typhimurium, FlgM inhibits the activity of SigD, but an additional element
is involved in determining the number of flagellar filaments.
Copyright © 1996, American Society for Microbiology
Role of FlgM in sigma D-dependent gene expression in Bacillus subtilis
Dipartimento di Genetica e Microbiologia "A. Buzzati-Traverso", Universita degli Studi, Pavia, Italy.
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