Metabolic Perturbations Caused by the Over-Expression of mcr-1 in Escherichia coli

Abstract

Rapid dissemination of the plasmid-born polymyxin resistance gene <i>mcr-1</i> poses a critical medical challenge. MCR-1 expression is tightly controlled and imposes a fitness cost on the bacteria. We used growth studies and metabolomics to examine growth and metabolic changes within <i>E. coli</i> TOP10 at 8 and 24 h in response to different levels of expression of <i>mcr-1</i>. Induction of <i>mcr-1</i> greatly increased expression at 8 h and markedly reduced bacterial growth; membrane disruption and cell lysis were evident at this time. At 24 h, the expression of <i>mcr-1</i> dramatically declined with restored growth and membrane integrity, indicating regulation of <i>mcr-1</i> expression in bacteria to maintain membrane homeostasis. Intermediates of peptide and lipid biosynthesis were the most commonly affected metabolites when <i>mcr-1</i> was overexpressed in <i>E. coli</i>. Cell wall biosynthesis was dramatically affected with the accumulation of lipids including fatty acids, glycerophospholipids and lysophosphatidylethanolamines, especially at 8 h. In contrast, levels of intermediate metabolites of peptides, amino sugars, carbohydrates and nucleotide metabolism and secondary metabolites significantly decreased. Moreover, the over-expression of <i>mcr-1</i> resulted in a prolonged reduction in intermediates associated with pentose phosphate pathway and pantothenate and CoA biosynthesis. These findings indicate that over-expression of <i>mcr-1</i> results in global metabolic perturbations that mainly involve disruption to the bacterial membrane, pentose phosphate pathway as well as pantothenate and CoA biosynthesis.