title: Exposure to the proton scavenger glycine under alkaline conditions induces Escherichia coli viability loss.
abstract: Our previous work described a clear loss of Escherichia coli (E. coli) membrane integrity after incubation with glycine or its N-methylated derivatives N-methylglycine (sarcosine) and N,N-dimethylglycine (DMG), but not N,N,N-trimethylglycine (betaine), under alkaline stress conditions. The current study offers a thorough viability analysis, based on a combination of real-time physiological techniques, of E. coli exposed to glycine and its N-methylated derivatives at alkaline pH. Flow cytometry was applied to assess various physiological parameters such as membrane permeability, esterase activity, respiratory activity and membrane potential. ATP and inorganic phosphate concentrations were also determined. Membrane damage was confirmed through the measurement of nucleic acid leakage. Results further showed no loss of esterase or respiratory activity, while an instant and significant decrease in the ATP concentration occurred upon exposure to either glycine, sarcosine or DMG, but not betaine. There was a clear membrane hyperpolarization as well as a significant increase in cellular inorganic phosphate concentration. Based on these results, we suggest that the inability to sustain an adequate level of ATP combined with a decrease in membrane functionality leads to the loss of bacterial viability when exposed to the proton scavengers glycine, sarcosine and DMG at alkaline pH.
authors.affiliation: Department of Nutrition, Genetics and Ethology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium. Donna.Vanhauteghem@Ugent.be
authors.forename: Donna
authors.initials: D
authors.lastname: Vanhauteghem
authors.forename: Geert Paul Jules
authors.initials: GP
authors.lastname: Janssens
authors.forename: Angelo
authors.initials: A
authors.lastname: Lauwaerts
authors.forename: Stanislas
authors.initials: S
authors.lastname: Sys
authors.forename: Filip
authors.initials: F
authors.lastname: Boyen
authors.forename: Eric
authors.initials: E
authors.lastname: Cox
authors.forename: Evelyne
authors.initials: E
authors.lastname: Meyer
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000468:Alkalies / Q000494:pharmacology*; D001622:Betaine / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D015169:Colony Count, Microbial; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D004950:Esterases / Q000378:metabolism; D005434:Flow Cytometry; D005453:Fluorescence; D005998:Glycine / Q000494:pharmacology*; D006706:Homeostasis / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007211:Indoles / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects*; D010710:Phosphates / Q000378:metabolism; D011522:Protons; D012521:Sarcosine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D000468:Alkalies; D007211:Indoles; D010710:Phosphates; D011522:Protons; D001622:Betaine; C007293:DAPI; C025138:dimethylglycine; D000255:Adenosine Triphosphate; D004950:Esterases; D005998:Glycine; D012521:Sarcosine
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