Typically, cells in nutrient-rich environments grow bigger than cells in nutrient-poor environments. The Levin lab determined that mutations in genes encoding the three enzymes resulted in cells that were small even when they were in a nutrient-rich environment. Basically, the cells had no way to tell the division apparatus to wait until theyve reached the size they should be. The cells would divide when they were still very short, said Levin. It was almost as if they were growing in really great media but they didnt know it.
Knowing when to divide
Further work indicated that the mutation perturbed FtsZ ring formation. In the cell, FtsZ exists in a balance between its unassembled and assembled state. The enzyme trio regulated FtsZ ring formation by changing this balancepushing FtsZ towards its unassembled state when the cells were growing in nutrient-rich conditions, thereby delaying cell division and increasing cell size.
All three enzymes in the pathway are sensitive to glucose levels, and the pathway is therefore well suited to communicating nutritional information directly to the cells division apparatus. In nutrient-poor conditions the enzymes no longer inhibit FtsZ assembly, allowing the FtsZ ring to form when the cells are still small, resulting in the formation of smaller daughter cells. The third enzyme in the pathway, UgtP, physically interacts with FtsZ to prevent ring formation. UgtP responds to low levels of glucose
Contact: Tony Fitzpatrick
Washington University in St. Louis