Pulsed high electric field causes 'all or nothing' membrane damage in Listeria monocytogenes and Salmonella typhimurium, but membrane H+-ATPase is not a primary target.
Salmonella typhimurium (CRA 1005) was more sensitive than Listeria monocytogenes (NCTC 11994) to pulsed high electric field (PHEF) treatment in distilled water (10, 15 and 20 kV/cm), 10 mM Tris-maleate buffer, pH 7.4 (15 kV/cm) and model beef broth (0.75%, w/v; 15 kV/cm). Sublethal injury could not be detected using a selective medium plating technique, indicating that bacterial inactivation by PHEF may be an 'all or nothing' event. PHEF-induced membrane permeabilisation resulted in an increase in the leakage of UV-absorbing material from the bacteria (UV-leakage) and a decreased ability of L. monocytogenes to maintain a pH gradient. A lack of correlation between the inhibition of H+-ATPase activity and PHEF treatment, cell viability or UV-leakage indicates that this enzyme is probably not a primary site of bacterial inactivation despite its role in the maintenance of internal pH.
Simpson
R K
RK
Department of Biological Sciences, Wye College, University of London, Ashford, Kent, UK. ryan.simpson@unilever.com
Whittington
R
R
Earnshaw
R G
RG
Russell
N J
NJ
D002462:Cell Membrane / Q000201:enzymology / Q000502:physiology; D002463:Cell Membrane Permeability / Q000502:physiology; D015169:Colony Count, Microbial; D004560:Electricity; D005452:Fluoresceins / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D005516:Food Microbiology; D006863:Hydrogen-Ion Concentration; D008089:Listeria monocytogenes / Q000201:enzymology / Q000254:growth & development* / Q000502:physiology; D008088:Listeriosis / Q000517:prevention & control; D010710:Phosphates / Q000032:analysis / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000032:analysis; D012478:Salmonella Food Poisoning / Q000517:prevention & control; D012486:Salmonella typhimurium / Q000201:enzymology / Q000254:growth & development* / Q000502:physiology; D013050:Spectrometry, Fluorescence
D005452:Fluoresceins; D005456:Fluorescent Dyes; D010710:Phosphates; C024098:6-carboxyfluorescein; D006180:Proton-Translocating ATPases