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Genes & Dev. 23 (8): 1014-1024

Copyright © 2009 by Cold Spring Harbor Laboratory Press.

A feeding tube model for activation of a cell-specific transcription factor during sporulation in Bacillus subtilis

Amy H. Camp, and Richard Losick1

Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachustts 02138, USA

Abstract: Spore formation by Bacillus subtilis takes place in a sporangium consisting of two chambers, the forespore and the mother cell, which are linked by pathways of intercellular communication. One pathway, which couples the activation of the forespore transcription factor {sigma}G to the action of {sigma}E in the mother cell, has remained mysterious. Traditional models hold that {sigma}E initiates a signal transduction pathway that specifically activates {sigma}G in the forespore. Recent experiments indicating that the mother cell and forespore are joined by a channel have led to the suggestion that a specific regulator of {sigma}G is transported from the mother cell into the forespore. As we report here, however, the requirement for the channel is not limited to {sigma}G. Rather, it is also required for the persistent activity of the early-acting forespore transcription factor {sigma}F as well as that of a heterologous RNA polymerase (that of phage T7). We infer that macromolecular synthesis in the forespore becomes dependent on the channel at intermediate stages of development. We propose that the channel is a gap junction-like feeding tube through which the mother cell nurtures the developing spore by providing small molecules needed for biosynthetic activity, including {sigma}G-directed gene activation.

Key Words: Bacillus subtilis • sporulation • cell–cell communication • feeding tube • gene regulation • {sigma}G

Received for publication January 14, 2009. Accepted for publication March 11, 2009.

1 Corresponding author.

E-MAIL losick{at}; FAX (617) 496-4642.

Article is online at

Supplemental material is available at

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