Previous Article | Next Article ![]()
Journal of Bacteriology, July 2001, p. 4052-4060, Vol. 183, No. 13
Department of Molecular and Cellular Biology, The
Biological Laboratories, Harvard University, Cambridge,
Massachusetts 02138,1 and
Chemie/Biochemie, Philipps-Universität Marburg, 35032 Marburg, Germany2
Received 19 December 2000/Accepted 6 April 2001
Entry into sporulation in Bacillus subtilis is
characterized by the formation of a polar septum, which asymmetrically
divides the developing cell into forespore (the smaller cell) and
mother cell compartments, and by migration of replication origin
regions to extreme opposite poles of the cell. Here we show that polar septation is closely correlated with movement of replication origins to
the extreme poles of the cell. Replication origin regions were visualized by the use of a cassette of tandem copies of
lacO that had been inserted in the chromosome near the
origin of replication and decorated with green fluorescent
protein-LacI. The results showed that extreme polar placement of
replication origin regions is not under sporulation control and
occurred in stationary phase under conditions under which entry into
sporulation was prevented. On the other hand, the formation of a polar
septum, which is under sporulation control, was almost invariably
associated with the presence of a replication origin region in the
forespore. Moreover, cells in which the polar placement of origin
regions was perturbed by deletion of the gene (smc) for
the structural maintenance of chromosomes (SMC) protein were impaired
in polar division. A small proportion (
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.13.4052-4060.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Coupling of Asymmetric Division to Polar Placement
of Replication Origin Regions in Bacillus
subtilis
1%) of the mutant cells were
able to undergo asymmetric division, but the forespore compartment of
these exceptional cells was generally observed to contain a replication
origin region. Immunofluorescence microscopy experiments indicated that
the block in polar division caused by the absence of SMC occurred at or prior to the step of bipolar Z-ring formation by the cell division protein FtsZ. A model is discussed in which polar division is under the
dual control of sporulation and an event associated with the placement
of a replication origin at the cell pole.
*
Corresponding author. Mailing address: Department of
Molecular and Cellular Biology, The Biological Laboratories, Harvard University, 16 Divinity Ave., Cambridge, MA 02138. Phone: (617) 495-4905. Fax: (617) 496-4642. E-mail:
losick{at}mail.mcb.harvard.edu.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»