Viability of Escherichia coli after combined osmotic and thermal treatment: a plasma membrane implication

Abstract

This study investigates the influence of temperature ( T) and osmotic pressure ( Π) on the viability of Escherichia coli K12 during an osmotic treatment. Osmotic shock (dehydration and rehydration within 1 s) in liquid media at different temperatures (4, 10, 30 and 37 °C) and different levels of osmotic pressure (26, 30, 35, 40, 82 and 133 MPa) were realized. Results show that a sudden dehydration, below 40 MPa, destroyed up to 80% of the bacterial population for each tested temperature, whereas viability was greater than 90% for an osmotic pressure less than 26 MPa. The influence of T and Π on the membrane's physical structure is finally considered to explain the results in light of FTIR and electron microscopy study of the influence of temperature and osmotic pressure on E. coli membrane phospholipids conformation.