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J Bacteriol, May 1998, p. 2285-2291, Vol. 180, No. 9
Department of Microbiology and Immunology,
School of Medicine, Emory University, Atlanta, Georgia 30322
Received 22 December 1997/Accepted 3 March 1998
Endospores of Bacillus subtilis are enclosed in a
proteinaceous coat which can be differentiated into a thick, striated
outer layer and a thinner, lamellar inner layer. We found that the
N-terminal sequence of a 25-kDa protein present in a preparation of
spore coat proteins matched that of the Mn-dependent superoxide
dismutase (SOD) encoded by the sodA locus.
sodA is transcribed throughout the growth and sporulation
of a wild-type strain and is responsible for the SOD activity detected
in total cell extracts prepared from B. subtilis.
Disruption of the sodA locus produced a mutant that
lacked any detectable SOD activity during vegetative growth and
sporulation. The sodA mutant was not impaired in the
ability to form heat- or lysozyme-resistant spores. However,
examination of the coat layers of sodA mutant spores
revealed increased extractability of the tyrosine-rich outer coat
protein CotG. We showed that this condition was not accompanied by
augmented transcription of the cotG gene in sporulating
cells of the sodA mutant. We conclude that SodA is required
for the assembly of CotG into the insoluble matrix of the spore and
suggest that CotG is covalently cross-linked into the insoluble matrix
by an oxidative reaction dependent on SodA. Ultrastructural analysis
revealed that the inner coat formed by a sodA mutant was
incomplete. Moreover, the outer coat lacked the characteristic striated
appearance of wild-type spores, a pattern that was accentuated in a
cotG mutant. These observations suggest that the
SodA-dependent formation of the insoluble matrix containing CotG is
largely responsible for the striated appearance of this coat layer.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Involvement of Superoxide Dismutase in Spore Coat
Assembly in Bacillus subtilis

*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, School of Medicine, Emory University, 3001 Rollins Research Center, Atlanta, GA 30322. Phone: (404) 727-5969. Fax: (404) 727-3659; E-mail: Moran{at}microbio.emory.edu.
Present address: Instituto de Tecnologia Química e
Biológica, Universidade Nova de Lisboa, Apartado 127, 2780 Oeiras Codex, Portugal.
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