Sigma Factor Exchange During Bacillus Subtilis Sporulation

University Of Texas Health Science Center San Antonio, San Antonio TX

Investigators

Abstract

Endospore formation in bacillus bacteria represents a simple differentiation in which the bacterium undergoes a series of physiological and morphological changes to generate a dormant cell form. At an early state in sporulation, Bacillus subtilis partitions itself into two unequal compartments, which are destined for unique developmental fates. The smaller forespore compartment becomes the spore. The larger mother cell compartment engulfs and nurtures the forespore, then lyses to release the mature spore to the environment. Each compartment's program of gene expression is controlled by the sequential appearance of unique transcription factors. SigmaE is the first of the mother cell-specific transcription factors. SigmaE is synthesized in the predivisional cell as an inactive proprotein (pro-sigmaE ), but becomes active only in the mother cell compartment. The mother cell specificity of sigmaE is likely due to two complementary mechanisms: the sequestration of pro-sigmaE to the mother cell side of the sporulation septum and the degradation of residual sigmaE in the forespore. This project will examine the sequestration element of this process. Mutational analyses will be used to identify the regions of pro-sigmaE and its processing enzyme which target them to the forespore septum. Once identified, these regions will be used as biochemical and/or genetic probes to identify the septal components responsible for sequestration to this site. Regulation of cellular processes by the spatial distribution of proteins is emerging as an important feature of prokaryotic biology. The Bacillus sporulation system is a well studied and tractable model which can be exploited to determine the mechanisms that underlie this phenomenon.