Question

You are a microbiologist working on a recently isolated species of bacteria. You start a culture of the bacterium growing at 15 degrees Celsius. In oder to study the membrane composition of this species, you then increase the growth temperature to 37 degrees Celsius. If this bacterium were "typical" what would you expect to see with regard to the fatty acid conpostion of the membrane? Why?

Answer 1

Answer :

Bacterial membrane consists of a phospholipid bilayer in which membrane proteins are embedded.

At lower temperatures, the lipid bilayer consists mostly of unsaturated fatty acids, but when temperature is raised, then saturated fatty acids become more common in the lipid bilayer.

This is because when temperature is raised, membrane structure undergoes a phase change from solid type to fluid type state. In a fluid state, staurated fatty acids can help to stabilise membrane structure as staurated fatty acids can be packed tightly in a linear structure.

On the other hand, unsaturated fatty acids contain double or triple bonds, and due to presence of kink in their structure, these fatty acids cannot be packed with efficiency at high temperature.

In conclusion, membranes are less fluid at lower temperature and can be maintained by unsaturated fatty acids, which helps in increasing membrane fluidity. But, upon increasing temperature, membrane fluidity increases and this tends to change membrane structure from solid type state into fluid type state. To stabilise the membrane in such a case, proportion of saturated fatty acids increase, which can be packed tightly and prevent membrane from melting at high temperature.

Hence, upon increasing temperature from 15°C to 37°C , proportion of saturated fatty acids would increase in the membrane as they can be packed more tightly and prevent membrane from melting or disintegrating at high temperature.