Alterations in AcylPhosphatidylglycerol Levels in ΔpagP, ΔpldB, and Δcls Escherichia coli Leads to Phenotypic Variance
Maryam Pourmaleki, Vassar College ’16 and Prof. Teresa GarrettPast studies have suggested that headgroup-acylated glycerophospholipids (GPLs), a low abundance class of lipids, are involved in cell membrane function during cell division in Escherichia coli. This study aims to characterize the cellular phenotype of E. coli when the levels of headgroup- acylated GPLs are altered. Three enzymes, PagP, PldB, and At1g78690 (AT), have been shown to play roles in the synthesis of headgroup-acylated GPLs in E. coli. PagP synthesizes acyl phosphatidylglycerol (acyl PG) in the outer membrane. PldB synthesizes acyl PG in the inner membrane. At1g78690 synthesizes GPLs by acylating lyso GPLs and, through an unknown mechanism, leads to an accumulation of acyl PG. Strains of wild-type (WT) MG1655 E. coli with pagP and pldB deletions, ΔpagP and ΔpldB, were transformed with an empty pBAD33.1 plasmid, or pBAD33.1 containing PagP, AT, or PldB. A triple cardiolipin synthase knockout mutant, BKT12, and its WT control, W3110, were transformed similarly. These strains, constructed to have altered acyl PG levels, were analyzed. Cellular morphology, temperature sensitivity, lipid composition, cellular permeability, and minimum inhibitory concentration to a variety of antibiotics was determined for each strain. Compared to the WT controls, overexpression of PldB leads to an elongation of cell length in BKT12, MG1655, ΔpagP, and ΔpldB. No strains showed temperature sensitivity. Overexpression of PagP leads to an altered growth rate and the presence of an additional unidentified lipid in all strains with the exception of WT W3110. Additionally, PagP overexpression leads to an increase in membrane permeability in all strains. There was no change in the minimum inhibitory concentrations upon expression of PagP, AT, or PldB. In the future, a ΔpldBΔpagP strain will be constructed and similarly analyzed to further shed light on the role of headgroup-acylated GPLs in the cell.