title: Glycine and its N-methylated analogues cause pH-dependent membrane damage to enterotoxigenic Escherichia coli.
abstract: The current study first investigates the emulsifying potential of glycine and its N-methylated derivatives N-methylglycine (sarcosine), N,N-dimethylglycine (DMG) and N,N,N-trimethylglycine (betaine) under varying pH conditions. Subsequently, the effect of these test compounds on the membrane integrity of enterotoxigenic Escherichia coli (ETEC) was evaluated. Oil in water emulsions containing each compound show that DMG is a more potent enhancer of emulsification than glycine, sarcosine and betaine under the conditions tested. Flow cytometry was used to investigate whether the emulsifying potential is associated with an effect on ETEC membrane integrity. The bacteria were exposed to each of the test compounds under varying pH conditions and membrane integrity was assessed using the LIVE/DEAD BacLight kit. Results show a membrane deteriorating effect caused by glycine, sarcosine and DMG, but not by betaine. This effect is pH- and time-dependent and has an apparent threshold at pH 9.0. Conventional plate counts confirmed concomitant changes in culturability of the membrane comprised bacteria.
authors.affiliation: Laboratory of Animal Nutrition, Department of Nutrition, Genetics and Ethology, Faculty of Veterinary Medicine, Ghent University, Heidestraat 19, 9820, Merelbeke, Belgium. Donna.Vanhauteghem@Ugent.be
authors.forename: D
authors.initials: D
authors.lastname: Vanhauteghem
authors.forename: G P J
authors.initials: GP
authors.lastname: Janssens
authors.forename: A
authors.initials: A
authors.lastname: Lauwaerts
authors.forename: S
authors.initials: S
authors.lastname: Sys
authors.forename: F
authors.initials: F
authors.lastname: Boyen
authors.forename: I D
authors.initials: ID
authors.lastname: Kalmar
authors.forename: E
authors.initials: E
authors.lastname: Meyer
mesh_terms: D001622:Betaine / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects* / Q000502:physiology; D045703:Emulsifying Agents / Q000494:pharmacology*; D054307:Enterotoxigenic Escherichia coli / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D005998:Glycine / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D034442:N-substituted Glycines / Q000494:pharmacology*; D012521:Sarcosine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D045703:Emulsifying Agents; D034442:N-substituted Glycines; D001622:Betaine; C025138:dimethylglycine; D005998:Glycine; D012521:Sarcosine