In vivo cell division gene product interactions in Escherichia coli K-12.

Overexpression of plasmid-coded PBP 3 was analyzed in strains harboring ftsA, ftsH, pbpB (ftsI), ftsQ, ftsZ, or recA441 (Tif) mutations. Higher cellular levels of PBP 3, the pbpB gene product, could not restore septum formation of ftsA, ftsQ, ftsZ, and recA (Tif) mutants at 42 degrees C. However, filamentation in strains harboring pbpB and ftsH mutations was fully suppressed by PBP 3 overexpression. Additional observations indicated that the Y16 (ftsH) strain, not transformed with the PBP 3-overproducing plasmid, had no detectable PBP 3 in envelopes after incubation at the restrictive temperature. These results suggest that suppression of filamentation of fts strains overexpressing wild-type cell division proteins after the shift to the restrictive temperature can be a useful strategy to demonstrate in vivo interactions of cell division gene products.