Open questions about the function and evolution of bacterial Min systems

Abstract

Probably one of the most controversial questions about the cell division of rod-shaped bacteria concerns the mechanism that ensures the correct placement of the division septum—mid-cell during vegetative growth but closer to one end during sporulation. In general, bacteria multiply by binary fission in which the division septum forms almost exactly at the cell center. How the division machinery achieves such accuracy is a question of continuing interest. Cell division in Escherichia coli and Bacillus subtilis are the most thoroughly studied cell division mechanisms. The earliest visible event in cell division is the formation of a Z ring by FtsZ, a tubulin like protein, at the future septum site. The Z-ring appears to be an accurate marker for the position of the division site and is furthermore recognized by set of cell division proteins—the divisome. At least two distinct mechanisms contribute to the placement of the division machinery: nucleoid occlusion and the Min system. The mechanism of Min system action is fundamentally different in both model organisms [reviewed in Barak and Wilkinson (2007)].