Membrane fluidity is a critical element in bacterial phenotype: it is the parameter that governs the rate of diffusion of membrane proteins. The fluidity of a membrane is modulated by the physical parameters of its environment, first and foremost by temperature: when the temperature drops, so does the fluidity of a membrane. In response to such stimuli, bacteria are known to change the composition of their membranes.
To quantify the changes in fluidity induced by these changes in composition, researchers from the ProCeD team, in collaboration with a team from the Science For Life Laboratory in Stockholm, have developed a new method, published in the Biophysical Journal.
The principle behind this technique is simple: a fluorescent dye is injected into the membrane of a bacterial cell to measure its diffusion rate. The faster the speed of the tracer, the greater the fluidity. Using this technique, the researchers were able to measure the relative changes in fluidity of B. subtilis in response to a change in temperature. Their experiments showed that while the B. subtilis membrane adapts its fluidity in response to a change in temperature, this adaptation is incomplete and membrane fluidity is lower at 20°C than at 37°C.
This purely biophysical technique is easy to adapt from one bacterium to another. To demonstrate this, the researchers also studied the response to cold of the pathogen Staphylococcus aureus, which is much less well known than that of B. subtilis.
Contact: Aurélien Barbotin & Rut Carballido-López
