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Journal of Bacteriology, February 1999, p. 781-790, Vol. 181, No. 3
Department of Molecular and Cellular Biology,
The Biological Laboratories, Harvard University, Cambridge,
Massachusetts 02138
Received 19 October 1998/Accepted 17 November 1998
We report the use of a fusion to the green fluorescent protein to
visualize the assembly of the morphogenetic protein SpoIVA around the
developing forespore during the process of sporulation in the bacterium
Bacillus subtilis. Using a deconvolution algorithm to
process digitally-collected optical sections, we show that SpoIVA,
which is synthesized in the mother cell chamber of the sporangium,
assembled into a spherical shell around the outer surface of the
forespore. Time-lapse fluorescence microscopy showed that this assembly
process commenced at the time of polar division and seemed to continue
after engulfment of the forespore was complete. SpoIVA remained present
throughout the late stages of morphogenesis and was present as a
component of the fully mature spore. Evidence indicates that assembly
of SpoIVA depended on the extreme C-terminal region of the protein and
an additional region that directly or indirectly facilitated
interaction among SpoIVA molecules. The N- and C-terminal regions of
SpoIVA, including the extreme C terminus, are highly similar to the
corresponding regions of the homologous protein from the distantly
related endospore-forming bacterium Clostridium
acetobutylicum, attesting to their importance in the function of
the protein. Finally, we show that proper localization of SpoIVA
required the expression of one or more genes which, like
spoIVA, are under the control of the mother cell
transcription factor
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
A Four-Dimensional View of Assembly of a
Morphogenetic Protein during Sporulation in Bacillus
subtilis
E. One such gene was
spoVM, whose product was required for efficient targeting
of SpoIVA to the outer surface of the forespore.
*
Corresponding author. Mailing address: Department of
Molecular and Cellular Biology, The Biological Laboratories, Harvard University, Cambridge, MA 02138. Phone: (617) 495-1774. Fax: (617) 496-4642. E-mail: losick{at}biosun.harvard.edu.
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