CEDA IS A NOVEL ESCHERICHIA-COLI PROTEIN THAT ACTIVATES THE CELL-DIVISION INHIBITED BY CHROMOSOMAL DNA OVER-REPLICATION

We isolated and characterized a new gene related to the control of cel l division regulation in Escherichia coli, At 30 degrees C, the dnaAco s mutant causes over-replication of the chromosome, and colony formati on is inhibited. We found that, at this temperature, the dnaAcos cells form filaments; therefore, septum formation is inhibited, This inhibi tion was independent of SfiA, an inhibitor of the septum-forming prote in, FtsZ. To identify factors involved in this pathway of inhibition, we isolated seven multicopy suppressors for the cold-sensitive phenoty pe of the dnaAcos mutant. One of these proved to be a previously unkno wn gene, which we named cedA, This gene encoded a 12 kDa protein and r esided at 38.9 min on the E. coli genome map, A multicopy supply of th e cedA gene to the dnaAcos cells did not repress over-replication of t he chromosome but did stimulate cell division of the host, the result being growth of cells with an abnormally elevated chromosomal copy num ber, Therefore, the expression level of the cedA gene seems to be impo rtant for inhibiting cell division of the dnaAcos mutant at 30 degrees C. We propose that overreplication of the chromosome activates a path way for inhibiting cell division and that the cedA gene modulates this division control, In the dnaA(+) background, cedA also seems to affec t cell division.