Escherichia coli and Lactobacillus plantarum responses to osmotic stress.
Escherichia coli and Lactobacillus plantarum were subjected to final water potentials of -5.6 MPa and -11.5 MPa with three solutes: glycerol, sorbitol and NaCl. The water potential decrease was realized either rapidly (osmotic shock) or slowly (20 min) and a difference in cell viability between these conditions was only observed when the solute was NaCl. The cell mortality during osmotic shocks induced by NaCl cannot be explained by a critical volume decrease or by the intensity of the water flow across the cell membrane. When the osmotic stress is realized with NaCl as the solute, in a medium in which osmoregulation cannot take place, the application of a slow decrease in water potential resulted in the significant maintenance of cell viability (about 70-90%) with regard to the corresponding viability observed after a sudden step change to same final water potential (14-40%). This viability difference can be explained by the existence of a critical internal free Na+ concentration.
Poirier
I
I
Laboratoire de génie des Procédés Alimentaires et Biotechnologiques, E.N.S.B.A.N.A., Dijon, France.
Maréchal
P A
PA
Evrard
C
C
Gervais
P
P
D048429:Cell Size; D002470:Cell Survival; D003470:Culture Media; D004926:Escherichia coli / Q000166:cytology / Q000502:physiology*; D005990:Glycerol / Q000737:chemistry; D007778:Lactobacillus / Q000166:cytology / Q000502:physiology*; D008858:Microscopy, Phase-Contrast; D009997:Osmotic Pressure; D012965:Sodium Chloride / Q000737:chemistry; D013012:Sorbitol / Q000737:chemistry; D013053:Spectrophotometry
D003470:Culture Media; D012965:Sodium Chloride; D013012:Sorbitol; D005990:Glycerol