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A novel pathway of intercellular signalling in Bacillus subtilis involves a protein with similarity to a component of type III secretion channels
Author(s) -
Camp Amy H.,
Losick Richard
Publication year - 2008
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2008.06289.x
Subject(s) - biology , bacillus subtilis , sigma factor , microbiology and biotechnology , secretion , intracellular , translocase , gene , genetics , biochemistry , rna , rna polymerase , chromosomal translocation , bacteria
Summary During spore formation in Bacillus subtilis , σ E ‐directed gene expression in the mother‐cell compartment of the sporangium triggers the activation of σ G in the forespore by a pathway of intercellular signalling that is composed of multiple proteins of unknown function. Here, we confirm that the vegetative protein SpoIIIJ, the forespore protein SpoIIQ and eight membrane proteins (SpoIIIA A through SpoIIIA H ) produced in the mother cell under the control of σ E are ordinarily required for intercellular signalling. In contrast, an anti‐σ G factor previously implicated in the pathway is shown to be dispensable. We also present evidence suggesting that SpoIIIJ is a membrane protein translocase that facilitates the insertion of SpoIIIAE into the membrane. In addition, we report the isolation of a mutation that partially bypasses the requirement for SpoIIIJ and for SpoIIIAA through SpoIIIAG, but not for SpoIIIAH or SpoIIQ, in the activation of σ G . We therefore propose that under certain genetic conditions, SpoIIIAH and SpoIIQ can constitute a minimal pathway for the activation of σ G . Finally, based on the similarity of SpoIIIAH to a component of type III secretion systems, we speculate that signalling is mediated by a channel that links the mother cell to the forespore.