CHROMOSOME AND LOW COPY PLASMID SEGREGATION IN ESCHERICHIA-COLI - VISUAL EVIDENCE FOR DISTINCT MECHANISMS

We have investigated DNA segregation in E. coli by inserting multiple lac operator sequences into the chromosome near the origin of replicat ion (oriC), in the hisC gene, a terminus marker, and into plasmids P1 and F. Expression of a GFP-LacI fusion protein allowed visualization o f lac operator localization. oriC was shown to be specifically localiz ed at or near the cell poles, and when duplicated, one copy moved to t he site of new pole formation near the site of cell division. In contr ast, P1 and F localized to the cell center and on duplication appeared to move rapidly to the quarter positions in the cell. Our analysis su ggests that different active processes are involved in movement and lo calization of the chromosome and of the two plasmids during segregatio n.