Compartmentalization of the periplasm at cell division sites in Escherichia coli as shown by fluorescence photobleaching experiments.

Morphological evidence has previously indicated that the periplasmic space of Escherichia coli is compartmentalized at sites corresponding to future sites of cell division. The borders of these morphological compartments are formed by localized zones of adhesion (periseptal annuli). In the present study, the technique of fluorescence recovery after photobleaching was used to determine whether these structures act as barriers to the free movement of proteins within the periplasm. The recovery of fluorescence in the ftsA filaments was found to be uniformly low over at potential sites of cell division and at the cell poles, indicating that these regions are biochemically sequestered from the remainder of the periplasmic space. Our results provide direct evidence for local compartments within the periplasm, primarily located at the sites of past or future cell divisions. The implications of this finding for cell division and other periplasmic processes are discussed.