LOCALIZATION AND FUNCTION OF EARLY CELL-DIVISION PROTEINS IN FILAMENTOUS ESCHERICHIA-COLI-CELLS LACKING PHOSPHATIDYLETHANOLAMINE

Escherichia coli cells that contain the pss-93 null mutation are compl etely deficient in the major membrane phospholipid phosphatidylethanol amine (PE), Such cells are defective in cell division. To gain insight into how a phospholipid defect could block cytokinesis, we used fluor escence techniques on whole cells to investigate which step of the cel l division cycle was affected. Several proteins essential for early st eps in cytokinesis, such as FtsZ, ZipA, and FtsA, were able to localiz e as bands to potential division sites in pss-93 filaments, indicating that the generation and localization of potential division sites was not grossly affected by the absence of PE, However, there was no evide nce of constriction at most of these potential division sites. FtsZ an d green fluorescent protein (GFP) fusions to FtsZ and ZipA often forme d spiral structures in these mutant filaments. This is the first repor t of spirals formed by wild-type FtsZ expressed at normal levels and b y ZipA-GFP, The results suggest that the lack of PE may affect the cor rect interaction of FtsZ with membrane nucleation sites and alter FtsZ ring structure so as to prevent or delay its constriction.