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Journal of Bacteriology, August 2000, p. 4491-4499, Vol. 182, No. 16
Department of Biology, Virginia Polytechnic
Institute and State University, Blacksburg, Virginia 24061
Received 28 March 2000/Accepted 23 May 2000
A major structural element of bacterial endospores is a
peptidoglycan (PG) wall. This wall is produced between the two opposed membranes surrounding the developing forespore and is composed of two
layers. The inner layer is the germ cell wall, which appears to have a
structure similar to that of the vegetative cell wall and which serves
as the initial cell wall following spore germination. The outer layer,
the cortex, has a modified structure, is required for maintenance of
spore dehydration, and is degraded during spore germination. Theories
suggest that the spore PG may also play a mechanical role in the
attainment of spore dehydration. Inherent in one of these models is the
production of a gradient of cross-linking across the span of the spore
PG. We report analyses of the structure of PG found within immature,
developing Bacillus subtilis forespores. The germ cell wall
PG is synthesized first, followed by the cortex PG. The germ cell wall
is relatively highly cross-linked. The degree of PG cross-linking drops
rapidly during synthesis of the first layers of cortex PG and then
increases two- to eightfold across the span of the outer 70% of the
cortex. Analyses of forespore PG synthesis in mutant strains reveal
that some strains that lack this gradient of cross-linking are able to
achieve normal spore core dehydration. We conclude that spore PG with
cross-linking within a broad range is able to maintain, and possibly to
participate in, spore core dehydration. Our data indicate that the
degree of spore PG cross-linking may have a more direct impact on the rate of spore germination and outgrowth.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Structural Analysis of Bacillus subtilis
Spore Peptidoglycan during Sporulation
*
Corresponding author. Mailing address: Department of
Biology, 2119 Derring Hall MC0406, Blacksburg, VA 24061. Phone: (540) 231-2529. Fax: (540) 231-9307. E-mail: dpopham{at}vt.edu.
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