Cell division is one of the most fundamental processes in living cells. Relatively little is known about how cells position their division site so that daughter cells with appropriate properties are generated. Rod shaped bacteria such as Bacillus subtilis divide precisely at the mid point of the long axis of the cell. In rod shaped bacteria, generally, it was thought that two negative regulators cooperate to direct the division machinery to this site. One well characterized system, Min (after the minicells that the mutants produce) prevents cell division from occurring inappropriately close to the existing cell poles.
A second hypothetical system called nucleoid occlusion was postulated to prevent division elsewhere along the length of the cell and to work by somehow sensing the position of the replicating and segregating chromosomes. Unfortunately, for about 15 years nothing was known about how nucleoid occlusion works.Wu and Errington solved this problem by discovering the existence of a gene now called noc (nucleoid occlusion) that encodes a non-specific DNA binding protein that is also an inhibitor of division. This work finally established the existence of the nucleoid occlusion effect and provided a molecular basis for selection of the mid-cell site for cell division in B. subtilis.
Wu, L.J. and Errington, J. (2004) Coordination of cell division and chromosome segregation by a nucleoid occlusion protein in Bacillus subtilis. Cell 117, 915-925.