Effect of cell membrane fatty acid composition of Escherichia coli on the resistance to pulsed electric field (PEF) treatment

• PEF resistance of E. coli at stationary phase was related to the fluidity of membrane.
• PEF resistance of E. coli at stationary was related to lipid composition of membrane.
• Results confirmed by the determination of cytomembrane fluidity of E. coli.
• Fluidity isn't key factor determining PEF resistance of E. coli at exponential phase.

The underlying relationships between growth temperature, membrane fatty acid composition (mFAC) and PEF resistance of Escherichia coli (E. coli) were explored. Results indicated the PEF resistance of E. coli at stationary stage was directly related to mFAC. For the cells at stationary stage, as growth temperature decreased from 37 °C to 15 °C, the PEF (23.3 kV/cm, 1.2 ms) lethality of E. coli was increased 1.5 log10, reached 3.2 log10. Meanwhile, the proportion of unsaturated fatty acid (UFA) was increased from 20.07 to 47.65%. And the fluidity index (FI) of the cell membrane was also increased from 0.42 to 1.42. It revealed that the PEF resistance of E. coli at stationary stage was determined by the mFAC and fluidity of the cell membrane. Those conclusions were also confirmed by cytomembrane fluidity determined by fluorescence probe (DPH) and the different PEF-induced electro-permeabilization of dioleoyl-sn-glycero-3-phosphocholine (DOPC) and Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) vesicles. On the other hand, for the cell at exponential stage, the PEF resistance of E. coli was rarely affected by mFAC. The PEF (23.3 kV/cm, 1.2 ms) lethality of cells was almost the same (3.2 log10) at different growth temperature.