EnhancingEscherichia coliAbiotic Stress Resistance through Ornithine Lipid Formation

Abstract

AbstractEscherichia coliis a common host for biotechnology and synthetic biology applications. During growth and fermentation, the microbes are often exposed to stress conditions, such as variations in pH or solvent concentrations. Bacterial membranes play a key role in response to abiotic stresses. Ornithine lipids (OLs) are a group of membrane lipids whose presence and synthesis have been related to stress resistance in bacteria. We wondered if this stress resistance could be transferred to bacteria not encoding the capacity to form OLs in their genome, such asE. coli. In this study, we engineered differentE. colistrains to produce unmodified OLs and hydroxylated OLs by expressing the synthetic operonolsFC. Our results showed that OL formation improved pH resistance and increased biomass under phosphate limitation. Transcriptome analysis revealed that OL-forming strains differentially expressed stress- and membrane-related genes. OL-producing strains also showed better growth in the presence of the ionophore carbonyl cyanide 3-chlorophenylhydrazone (CCCP), suggesting reduced proton leakiness in OL-producing strains. Furthermore, our engineered strains showed improved heterologous violacein production at phosphate limitation and also at low pH. Overall, this study demonstrates the potential of engineering theE. colimembrane composition for constructing robust hosts with an increased abiotic stress resistance for biotechnology and synthetic biology applications.KeypointsTheE. colimembrane composition was engineered by producing ornithine lipidsOrnithine lipid production increase biomass yield under phosphate limitationEngineered strains show enhanced production phenotype under low pH stressTranscriptome analysis and CCCP experiments revealed reduced proton leakageGraphical abstract