LAUSR

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) using a primary ion beam of (CO2)6k+ was used to analyse chemical changes in the bacterial envelope of a fabF knock‐out Escherichia coli strain. fabF is the gene coding for FabF, the enzyme involved in the elongation of FA(16:1) to FA(18:1) and has been associated with plasmid transfer that can lead to acquired multiantibiotic resistance. Comparison of the membrane composition between fabF mutant E. coli and wild type E. coli during the logarithmic and stationary growth phases at two culture temperatures (37°C and 30°C) revealed substantial depletion of FA(18:1) in the fabF mutant during logarithmic growth that resulted in a correlated reduction in FA(cp19:0) during stationary phase. While no clear temperature dependence on the effect of the fabF mutation was found, a reduction in cyclopropanation was observed at lower culture temperature in the wild type strain. Additionally, depth profile analysis revealed a ‘thickening’ of the lipid A layer on the surface of the bacteria during stationary phase and also the appearance of cyclic enterobacterial common antigen (ECACYC) below the surface of the bacteria upon the shift from logarithmic to stationary growth phase.