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J. Bacteriol., Jul 1995, 3736-3742, Vol 177, No. 13
KA Hicks and AD Grossman
spo0H encodes a sigma factor, sigma-H, of RNA polymerase that is required
for sporulation in Bacillus subtilis. Null mutations in spo0H block the
initiation of sporulation but have no obvious effect on vegetative growth.
We have characterized an insertion mutation, csh203::Tn917lac, that makes
spo0H essential for normal growth. In otherwise wild-type cells, the
csh203::Tn917lac insertion mutation has no obvious effect on cell growth,
viability, or sporulation. However, in combination with a mutation in
spo0H, the csh203 mutation causes a defect in vegetative growth. The
csh203::Tn917lac insertion mutation was found to be located within orf23,
the first gene of the rpoD (sigma- A) operon. The transposon insertion
separates the major vegetative promoters P1 and P2 from the coding regions
of two essential genes, dnaG (encoding DNA primase) and rpoD (encoding the
major sigma factor, sigma-A) and leaves these genes under the control of
minor promoters, including P4, a promoter controlled by sigma-H. The chs203
insertion mutation caused a 2- to 10-fold increase in expression of
promoters recognized by RNA polymerase containing sigma-H. The increased
expression of genes controlled by sigma-H in the csh203 single mutant, as
well as the growth defect of the csh203 spo0H double mutant, was due to
effects on rpoD and not to a defect in orf23 or dnaG.
Copyright © 1995, American Society for Microbiology
Characterization of csh203::Tn917lac, a mutation in Bacillus subtilis that makes the sporulation sigma factor sigma-H essential for normal vegetative growth
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
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