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Journal of Bacteriology, October 2006, p. 7267-7273, Vol. 188, No. 20
0021-9193/06/$08.00+0 doi:10.1128/JB.00744-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
G That Is Independent of
E and of Engulfment
Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
Received 24 May 2006/ Accepted 1 August 2006
Formation of spores by Bacillus subtilis is characterized by cell compartment-specific gene expression directed by four RNA polymerase
factors, which are activated in the order
F-
E-
G-
K. Of these,
G becomes active in the prespore upon completion of engulfment of the prespore by the mother cell. Transcription of the gene encoding
G, spoIIIG, is directed in the prespore by RNA polymerase containing
F but also requires the activity of
E in the mother cell. When first formed,
G is not active. Its activation requires expression of additional
E-directed genes, including the genes required for completion of engulfment. Here we report conditions in which
G becomes active in the prespore in the absence of
E activity and of completion of engulfment. The conditions are (i) having an spoIIIE mutation, so that only the origin-proximal 30% of the chromosome is translocated into the prespore, and (ii) placing spoIIIG in an origin-proximal location on the chromosome. The main function of the
E-directed regulation appears to be to coordinate
G activation with the completion of engulfment, not to control the level of
G activity. It seems plausible that the role of
E in
G activation is to reverse some inhibitory signal (or signals) in the engulfed prespore, a signal that is not present in the spoIIIE mutant background. It is not clear what the direct activator of
G in the prespore is. Competition for core RNA polymerase between
F and
G is unlikely to be of major importance.
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