Several bacteriophage that infect bacteria produce just a few copies of their genomes, which, during cell division of their host, are faithfully segregated into the daughter cells. Li and Austin marked the P1 plasmid of Escherichia coli with green fluorescent protein fused to the partition (par) proteins of the phage, and then watched to see what happened to the plasmids during the cell cycle. Foci containing one or a few copies of the plasmid were captured at the center of growing cells and remained in place until just before the septum between the new cells was completed. At this point, the plasmid focus divided and then flew apart along the long axis of the cell, releasing the plasmid copies into the newly partitioned daughter cells. Interestingly, the plasmid seems to exert considerable control over host cell division; if mutant plasmids were used that did not separate, cell division was significantly delayed and was often aberrant. -- CA
Molec. Microbiol. 46, 63 (2002).
