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Journal of Bacteriology, October 2000, p. 5505-5512, Vol. 182, No. 19
Department of Biochemistry, University of
Connecticut Health Center, Farmington, Connecticut
06032,1 and Department of Microbiology
and Immunology, Loyola University School of Medicine, Maywood, Illinois
601532
Received 4 May 2000/Accepted 10 July 2000
Spores of Bacillus subtilis with a mutation in
spoVF cannot synthesize dipicolinic acid (DPA) and are too
unstable to be purified and studied in detail. However, the spores of a
strain lacking the three major germinant receptors (termed
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Characterization of Spores of Bacillus
subtilis Which Lack Dipicolinic Acid
ger3), as well as spoVF, can be isolated,
although they spontaneously germinate much more readily than
ger3 spores. The
ger3 spoVF spores lack DPA and have higher levels of core water than
ger3
spores, although sporulation with DPA restores close to normal levels
of DPA and core water to
ger3 spoVF spores. The DPA-less
spores have normal cortical and coat layers, as observed with an
electron microscope, but their core region appears to be more hydrated
than that of spores with DPA. The
ger3 spoVF spores also
contain minimal levels of the processed active form (termed
P41) of the germination protease, GPR, a finding consistent
with the known requirement for DPA and dehydration for GPR
autoprocessing. However, any P41 formed in
ger3
spoVF spores may be at least transiently active on one of this
protease's small acid-soluble spore protein (SASP) substrates, SASP-
. Analysis of the resistance of wild-type,
ger3,
and
ger3 spoVF spores to various agents led to the
following conclusions: (i) DPA and core water content play no role in
spore resistance to dry heat, dessication, or glutaraldehyde; (ii) an
elevated core water content is associated with decreased spore
resistance to wet heat, hydrogen peroxide, formaldehyde, and the
iodine-based disinfectant Betadine; (iii) the absence of DPA increases
spore resistance to UV radiation; and (iv) wild-type spores are more resistant than
ger3 spores to Betadine and
glutaraldehyde. These results are discussed in view of current models
of spore resistance and spore germination.
*
Corresponding author. Mailing address: Department of
Biochemistry, MC-3305, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06032. Phone: (860) 679-2607. Fax:
(860) 679-3408. E-mail: setlow{at}sun.uchc.edu.
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