title: Changes in the surface potential of Lactobacillus acidophilus under freeze-thawing stress.
abstract: The zeta potential of Lactobacillus acidophilus CRL 640, a measure of the net distribution of electrical charges on the bacterial surface, is a function of the glucose concentration in the growing media. With 2% glucose, cells in the stationary phase showed a zeta potential of -45 +/- 2 mV. With these cells, the zeta potential after freezing and thawing decreased to -32 +/- 2 mV and there was a decrease in viability. The changes in the surface potential correlated with damage to the cell surface as shown by electron microscopy. Freeze-thawed cells incubated in a rich medium recovered a zeta potential of -38 +/- 2 mV without cell growth. L. acidophilus CRL 640 showed the same value of surface potential as control cells when they were frozen and thawed in 2 M glycerol.
authors.affiliation: Centro de Referencia para Lactobacilos (CERELA), Chacabuco 145, San Miguel de Tucumán, Tucumán, Argentina.
authors.forename: M L
authors.initials: ML
authors.lastname: Fernńdez Murga
authors.forename: G
authors.initials: G
authors.lastname: Font de Valdez
authors.forename: A E
authors.initials: AE
authors.lastname: Disalvo
mesh_terms: D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D015925:Cryopreservation; D003451:Cryoprotective Agents / Q000494:pharmacology; D003470:Culture Media / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D005990:Glycerol / Q000494:pharmacology; D007779:Lactobacillus acidophilus / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D008564:Membrane Potentials / Q000187:drug effects; D008854:Microscopy, Electron
chemical_list: D003451:Cryoprotective Agents; D003470:Culture Media; D005947:Glucose; D005990:Glycerol