Temperature-mediated variations in cellular membrane fatty acid composition of Staphylococcus aureus in resistance to pulsed electric fields

Abstract

Effects of growth temperature on cell membrane fatty acid composition, fluidity and lethal and sublethal injury by pulsed electric fields (PEF) in Staphylococcus aureus ATCC 43300 (S. aureus) in the stationary phase were investigated. Analysis of the membrane fatty acids by gas chromatography-mass spectrometry (GC-MS) revealed that branched chain fatty acids (iso C14:0, iso C15:0, anteiso C15:0 and anteiso C17:0) and straight chain fatty acids (C12:0, C14:0, C16:0, C17:0 and C18:0) were primary constituents in the membrane. The S. aureus changed its membrane fatty acid composition and its overall fluidity when exposed to different temperatures. The PEF lethal and sublethal effects were assessed, and results suggested that the degree of inactivation depended on the cell membrane structure, electric field strength and treatment time. The PEF inactivation kinetics including lethal and sublethal injury fractions were fitted with non-linear Weibull distribution, suggesting that inactivation of the first log cycle of S. aureus population was significantly affected by growth temperature, and the membrane of cells became more fluid, and easier to induce electroportion in low temperatures. Moreover, the morphology of S. aureus cells were investigated by electron microscopy, showing that various temperature-modified cells were distorted to differing extents and some even collapsed due to deep irreversible electroporation after PEF treatment.

Variations in cellular membrane fatty acid composition ofEscherichia coliin resistance to pulsed electric fields induced by eugenol

“…These observations revealed that EUG affected the morphology of E. coli cell membranes and PEF treatment resulted in damage to the integrity of E. coli cell membrane, which likely caused a decrease in reduction of log cycles of E. coli (Patrignani, Vannini, Kamdem, Lanciotti, & Guerzoni, ). These changes were similar to a previous study on inactivation of Staphylococcus aureus under PEF treatment (Wang, Wang, Zeng, & Liu, ), which showed PEF treatment could lead to structural changes of the microbiological cell membrane.…”

“…Higher membrane fluidity was induced with an increase in EUG concentration, which likely reduced PEF resistance of E. coli cells. Previous studies have indicated that PEF inactivation could be enhanced due to an increase in membrane fluidity (Wang, Wang, Zeng, & Liu, 2016;Yun et al, 2017). Such changes of PEF resistance of E. coli were ascribed to the variations of membrane fluidity induced by the change in membrane fatty acid composition of E. coli at different EUG concentrations.…”

Kocuria Bacterial Isolates from Radioactive Springs of Jáchymov spa (Joachimsthal) as Sources of Polyunsaturated Fatty Acids

“…The effect of growth temperature on fatty acid composition was well reported in many studies (e.g. Marr and Ingraham, 1962;Ray et al, 1971;Wang et al, 2016).…”

Characterisation ofStaphylococcus aureuslipids by nanoelectrospray ionisation tandem mass spectrometry (nESI-MS/MS)

“…Nevertheless, while 2D-TLC can provide accurate quantification of each lipid class, it requires large amounts of lipid extracts and does not provide specificity with regard to individual molecular species [14]. The application of targeted mass spectrometry methods has provided some insight into the chemical composition of specific S. aureus lipids [15,16], while gas chromatography mass spectrometry (GC-MS) has proved successful in determining the specific fatty acid composition of S. aureus following diverse genetic, chemical and environmental manipulations [17,18,19].…”