Impact of altering the headgroup‐acylated glycerophospholipid levels on Escherichia coli cells deficient in phosphatidylserine and phosphatidylethanolamine

Abstract

Escherichia coli contains a variety of glycerophospholipids (GPLs). Phosphatidylethanolamine (PE) is particularly important as it is the only zwitterionic phospholipid and makes up 70–80% of total GPLs. It is formed from CDP‐diacylglycerol by the action of phosphatidylserine synthase (Pss) and phosphatidylserine decarboxylase (Psd). Pss condenses CDP‐diacylglycerol and serine to form phosphatidylserine (PS) and releases cytidine monophosphate. PS is a short‐lived intermediate that is rapidly decarboxylated to PE by the Psd enzyme. This study investigates the impact of altering headgroup‐acylated GPLs (HAGPLs) has on E. coli that are deficient in Pss and Psd. Overexpression of the E. coli genes pldB and pagP or the Arabidopsis thaliana gene At1g78690, elevates the levels of the HAGPL acyl phosphatidylglycerol (acyl PG). The overexpression of the human calcium independent N‐acyl transferase (iNAT) increases the levels of the HAGPL N‐acyl phosphatidylethanolamine (N‐acyl PE) in the cells. We transformed E. coli with temperature sensitive mutations in pss and psd with plasmids that contain pldB, pagP, At1g78690 or iNAT behind an arabinose inducible promotor. For each strain, a variety of cellular phenotypes, such as temperature sensitivity, cell morphology, antibiotic resistance, membrane permeability, membrane fluidity and lipid composition, were determined. Expression of At1g78690 promotes reversion of the temperature sensitive phenotype of the pss mutant by, we hypothesize, creating conditions under which compensatory mutations are more likely to support high temperature growth. Expression of pagP results in a longer cell phenotype that will be further investigated using scanning electron microscopy. Additional experiments will use fluorescently‐tagged proteins involved in cell division to determine if the increased cell length is the result of cell division defects promoted by accumulation of HAGPLs.Support or Funding InformationNational Science Foundation Research at Undergraduate Institutions Grant #1516805 and #1152463, and National Science Foundation Major Instrumentations Grant #1039659