Organisms precisely regulate cell size to ensure that daughter cells have sufficient cellular material to thrive or to create specific cell types: a tiny sperm versus a gargantuan egg for example. In single-celled organisms such as yeast and bacteria nutrient availability is the primary determinant of cell size. In animal cells size is controlled in large part by a molecule that senses the blood sugar dependent hormone insulin.
Petra Levin, Ph.D., Assistant Professor of Biology at Washington University in St. Louis, and her laboratory have recently identified a trio of enzymes that act in concert to link nutrient availability to cell size in the soil bacterium Bacillus subtilis.
Levin and her lab are looking into the factors that control the timing and position of cell division in B. subtilis. B. subtilis serves as the model system for a large family of bacteria that includes the causative agents of several important diseases, including anthrax and botulism. By learning how these simple organisms regulate division, we can better understand why this process goes awry in cancer cells resulting in uncontrolled growth and aberrant division.
A primary focus of the Levin labs research is a protein called FtsZ. FtsZ is an ancestor of tubulin, the protein that is responsible for distributing duplicated chromosomes between dividing human cells. In bacteria, FtsZ forms a ring at the future division site. The FtsZ ring then recruits all other components necessary for cell division and serves as the scaffolding for the entire division process.
The factors that regulate FtsZ ring formation determine when and where the cell is going to divide. Theoretically a cell could divide anywhere and at anytime, said Brad Weart, a graduate student in Levins lab. The cell has to very precisely restrain that process so that it only happens when and where the cell wants it to happen.