Selection of the midcell division site in Bacillus subtilis through MinD-dependent polar localization and activation of MinC

The MinC component of the division site selection system in Escherichia coli interacts with FtsZ to prevent polymerization

Positioning of the Z ring at the midcell site in Escherichia coli is assured by the min system, which masks polar sites through topological regulation of MinC, an inhibitor of division. To study how MinC inhibits division, we have generated a MalE-MinC fusion that retains full biological activity. We find that MalE-MinC interacts with FtsZ and prevents polymerization without inhibiting FtsZ's GTPase activity. MalE-MinC19 has reduced ability to inhibit division, reduced affinity for FtsZ, and reduced ability to inhibit FtsZ polymerization. These results, along with MinC localization, suggest that MinC rapidly oscillates between the poles of the cell to destabilize FtsZ filaments that have formed before they mature into polar Z rings.

Dynamic movement of the ParA-like Soj protein of B. subtilis and its dual role in nucleoid organization and developmental regulation

The Spo0J and Soj proteins of B. subtilis belong to a widespread family of bacterial proteins required for accurate segregation of plasmids and chromosomes. Spo0J binds to several sites around the oriC region of the chromosome, which are organized into compact foci that may play a centromere-like role in active chromosome segregation. We now show that Soj has a role in organization or compaction of Spo0J-oriC complexes and possibly other regions of the nucleoid. This activity is accompanied by a dynamic localization pattern in which Soj protein undergoes assembly and disassembly into large nucleoid-associated patches on a timescale of minutes. The dynamic behavior of Soj, like its previously described transcriptional repression activity, is controlled by Spo0J. These interactions may constitute a checkpoint coupling developmental transcription to cell cycle progression.