Suppression of a thermosensitive zipA cell division mutant by altering amino acid metabolism

Abstract

ZipA is essential for cell division in Escherichia coli, acting early in the process to anchor polymers of FtsZ to the cytoplasmic membrane. Along with FtsA, FtsZ and ZipA form a proto-ring at midcell that recruits additional proteins to eventually build the division septum. Cells carrying the thermosensitive zipA1 allele divide fairly normally at 30°C in rich medium but cease dividing at temperatures above 34°C, forming long filaments. In a search for suppressors of the zipA1 allele, we found that deletions of specific genes involved in amino acid biosynthesis could partially rescue cell growth and division at 34°C or 37°C but not at 42°C. Notably, although a diverse group of amino acid biosynthesis gene deletions could partially rescue the growth of zipA1 cells at 34°C, only deletions of genes related to the biosynthesis of threonine, glycine, serine, and methionine could rescue growth at 37°C. Adding exogenous pyridoxal 5-phosphate (PLP), a cofactor for many of the enzymes affected by this study, partially suppressed zipA1 mutant thermosensitivity. For many of the deletions, PLP had an additive rescuing effect on the zipA1 mutant. Moreover, added PLP partially suppressed the thermosensitivity of ftsQ and ftsK mutants and weakly suppressed an ftsI mutant, but it failed to suppress ftsA or ftsZ thermosensitive mutants. Along with the ability of a deletion of metC to partially suppress the ftsK mutant, our results suggest that perturbations of amino acid metabolic pathways, particularly those that redirect the flow of carbon away from the synthesis of threonine, glycine, or methionine, are able to partially rescue some cell division defects.