Death of Escherichia coli during rapid and severe dehydration is related to lipid phase transition

Abstract

This study reports the effects of exposure to increasing osmotic pressure on the viability and membrane structure of Escherichia coli. Changes in membrane structure after osmotic stress were investigated by electron transmission microscopy, measurement of the anisotropy of the membrane fluorescent probe DPH (1,6-diphenyl-1,3,5-hexatriene) inserted in E. coli, and Fourier infrared spectroscopy (FTIR). The results show that, above a critical osmotic pressure of 35 MPa, the viability of the bacterium is drastically reduced (2 log decrease in survivors). Electron micrographs revealed a severe contraction of the cytoplasm and the formation of membrane vesicles at 40 MPa. Changes in DPH anisotropy showed that osmotic dehydration to 40 MPa promoted a decrease in the membrane fluidity of integral cells of E. coli. FTIR measurements showed that at 10-40 MPa a transition from lamellar liquid crystal to lamellar gel among the phospholipids extracted from E. coli occurred. Bacterial death resulting from dehydration can be attributed to the conjunction between membrane deformation, caused by the volumetric contraction, and structural changes of the membrane lipids. The influence of the latter on the formation of membrane vesicles and on membrane permeabilization at lethal osmotic pressure is discussed, since vesiculation is hypothetically responsible for cell death.

Global Transcriptional Analysis of Dehydrated Salmonella enterica Serovar Typhimurium

“…Dehydration of membrane bilayers increases van der Waal's interactions between adjacent phospholipids, contributing to membrane transition to the gel phase at ambient temperatures (59). This results in segregation of the membranes and aggregation of proteins, leading to leakage and loss of solutes (10). The finding that the ⌬ddg mutant was impaired in dehydration tolerance and LTP supports the idea that modification of the lipid A structure is essential for Salmonella persistence in a low-water environment.…”

Predicting the Concentration of Verotoxin-Producing Escherichia coli Bacteria during Processing and Storage of Fermented Raw-Meat Sausages

“…Acid tolerance is also based on the effectiveness of ion transport through the cell membrane to maintain a constant internal pH (64) and on the induction of proteins responsible for repairing the membrane (65). On the other hand, the mechanism responsible for the death of E. coli during exposure to increasing osmotic pressure has been reported to be a combination of membrane deformation and structural changes of the membrane lipids affecting permeability (66). Therefore, perturbations of the membrane properties associated with relatively high temperatures could be one of the factors causing the decrease of E. coli survival at inactivating pH and/or a w values.…”

Fe3+-saturated montmorillonite effectively deactivates bacteria in wastewater

“…In general, bacterial deactivation can be the result of: 1) direct mechanical breakage of outer cell membranes by sharp edged nanoparticles (Akhavan and Ghaderi, 2010;Liu et al, 2009;Situ and Samia, 2014); 2) chemical oxidative stress mediated cell injury that is induced by in situ production of reactive oxygen species (Krishnamoorthy et al, 2012;Su et al, 2009); and 3) dehydration of cell membrane (Beney et al, 2004). It is highly likely that the latter two bacterial deactivation mechanisms are at play when wastewater is exposed to Fe 3+ -saturated montmorillonite.…”