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J. Bacteriol., Jun 1995, 3394-3406, Vol 177, No. 12
AO Henriques, BW Beall, K Roland and CP Moran Jr
The outermost protective structure found in endospores of Bacillus subtilis
is a thick protein shell known as the coat, which makes a key contribution
to the resistance properties of the mature spore and also plays a role in
its interaction with compounds able to trigger germination. The coat is
organized as a lamellar inner layer and an electron-dense outer layer and
has a complex polypeptide composition. Here we report the cloning and
characterization of an operon, cotJ, located at about 62 degrees on the B.
subtilis genetic map, whose inactivation results in the production of
spores with an altered pattern of coat polypeptides. The cotJ operon was
identified by screening a random library of lacZ transcriptional fusions
for a conditional (inducer-dependent) Lac+ phenotype in cells of a strain
in which the structural gene (spoIIGB) for the early-acting, mother-cell-
specific transcriptional factor sigma E was placed under the control of the
IPTG (isopropyl-beta-D-thiogalactopyranoside)-inducible Pspac promoter.
Sequence analysis of cloned DNA from the cotJ region complemented by
genetic experiments revealed a tricistronic operon preceded by a strong
sigma E-like promoter. Expression of an SP beta- borne cotJ-lacZ fusion
commences at around h 2 of sporulation, as does expression of other sigma
E-dependent genes, and shows an absolute requirement for sigma E. Studies
with double-reporter strains bearing a cotJ-gusA fusion and lacZ fusions to
other cot genes confirmed that expression of cotJ is initiated during
sporulation prior to activation of genes known to encode coat structural
proteins (with the sole exception of cotE). An in vitro-constructed
insertion-deletion mutation in cotJ resulted in the formation of spores
with no detectable morphological or resistance deficiency. However,
examination of the profile of electrophoretically separated spore coat
proteins from the null mutant revealed a pattern that was essentially
identical to that of a wild-type strain in the range of 12 to 65 kDa,
except for polypeptides of 17 and 24 kDa, the putative products of the
second (cotJB) and third (cotJC) cistrons of the operon, that were missing
or reduced in amount in the coat of the mutant. Polypeptides of the same
apparent sizes are detected in spores of a cotE null mutant, on which basis
we infer that the products of the cotJ operon are required for the normal
formation of the inner layers of the coat or are themselves structural
components of the coat.(ABSTRACT TRUNCATED AT 400 WORDS)
Copyright © 1995, American Society for Microbiology
Characterization of cotJ, a sigma E-controlled operon affecting the polypeptide composition of the coat of Bacillus subtilis spores
Department of Microbiology and Immunology, School of Medicine, Emory University, Atlanta, Georgia 30322, USA.
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