вЂњBut we wanted to find out why Salmonella died at lower temperatures. вЂњWe know how high temperatures kill bacteria,вЂќ Ebrahimi said. By better understanding the mechanisms of bacterial death at elevated temperatures, these findings can potentially improve food safety strategies and provide more efficient ways to deactivate bacteria using shorter duration of heating at lower temperatures. 6) in Biophysical Journal (Cell Press) then developed an analytical model based on their experiments that correlated membrane damage, cytoplasmic leakage and cell death. The authors of a paper appearing today (Feb. They also studied heating time and heating method, either a slower ramp-up of heat or a sudden pulse of heat and found that pulsed heat was more effective at killing bacteria. The modified bacteria required higher energy to make the cell membranes permeable enough to leak small molecules. The researchers conducted multiple experiments using both wild-type and heat resistant Salmonella bacteria and correlated the electrical results with fluorescence measurement and standard microbiology protocols. As the bacteriaвЂ™s cell wall lost integrity, charged molecules were ejected from the cells into the solution containing the bacteria, and consequently the electrical conductivity of the solution changed.

In order to prove their hypothesis, the team developed a sensor that was sensitive to the changes in electrical conductance of the growth medium. Because these small molecules are mostly ionic, we expected a change of the electrical conductance.вЂќ As the cell wall weakens, it can allow small molecules to leak out. вЂњIf you heat them, the lipids that make up the cell wall vibrate. вЂњWe had a hypothesis that the Salmonella bacterium might die due to leakage of the cell wall,вЂќ Ebrahimi said.

student at Purdue University, Aida Ebrahimi, an assistant professor of electrical engineering, Penn State, has determined that mild heat stress at temperatures around 120В° F damages the bacteriaвЂ™s cell wall without rupturing them. Using droplet-based electrical sensors she developed as a Ph.D. The most economical way to kill the bacteria that cause common food-borne illnesses вЂ“ mostly caused by Salmonella enterica вЂ“ is heat, but the mechanisms that kill Salmonella at lower temperatures were not fully understood until now, according to a team of researchers.Д«acteria can develop ways to cope with heat shock, so it is important to develop a complete understanding of how heat kills them.

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