Abstract
Escherichia coli is the daily workhorse in molecular biology research labs and an important platform microorganism in white biotechnology. Its cytoplasmic membrane is primarily composed of the phospholipids phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and cardiolipin (CL). As in most other bacteria, the typical eukaryotic phosphatidylcholine (PC) is not a regular component of the E. coli membrane. PC is known to act as a substrate in various metabolic or catabolic reactions, to affect protein folding and membrane insertion, and to activate proteins that originate from eukaryotic environments. Options to manipulate the E. coli membrane to include non-native lipids such as PC might make it an even more powerful and versatile tool for biotechnology and protein biochemistry. This article outlines different strategies how E. coli can be engineered to produce PC and other methylated PE derivatives. Several of these approaches rely on the ectopic expression of genes from natural PC-producing organisms. These include PC synthases, lysolipid acyltransferases, and several phospholipid N-methyltransferases with diverse substrate and product preferences. In addition, we show that E. coli has the capacity to produce PC by its own enzyme repertoire provided that appropriate precursors are supplied. Screening of the E. coli Keio knockout collection revealed the lysophospholipid transporter LplT to be responsible for the uptake of lyso-PC, which is then further acylated to PC by the acyltransferase-acyl carrier protein synthetase Aas. Overall, our study shows that the membrane composition of the most routinely used model bacterium can readily be tailored on demand.Key points• Escherichia coli can be engineered to produce non-native methylated PE derivatives.• These lipids can be produced by foreign and endogenous proteins.• Modification of E. coli membrane offers potential for biotechnology and research.Graphical abstract
Highlights
All living cells are surrounded by membranes, which protect them from external threats and are important for the controlled import and export of molecules
Cultivation of E. coli in the presence of ethanolamine derivatives or LPC was performed in M9 or LB medium, respectively
An alternative pathway for PC biosynthesis has only recently been described in divergent bacteria such as the Gram-negative X. campestris and several Gram-positive Streptococcus species (Moser et al 2014; Joyce et al 2019)
Summary
All living cells are surrounded by membranes, which protect them from external threats and are important for the controlled import and export of molecules. Principles of bacterial lipid membrane synthesis of Gram-negative bacteria mostly derive from studying the model organism Escherichia coli. The cytoplasmic membrane of E. coli consists mainly of three phospholipids: JK and GV contributed to this study. It was shown that the phospholipid composition within the cytoplasmic membrane of Gram-negative bacteria is highly asymmetric, dynamic, and cell cycle dependent (Bogdanov et al 2020). Those results, among others, emphasize the plasticity of the E. coli membrane and its ability to adapt to changing conditions, which include challenges imposed by recombinant protein production and various biocatalytic processes (Gubellini et al 2011; Opekarová and Tanner 2003)
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