Final answer:
In a colder environment, bacterial cells may replace shorter-chain fatty acids in their membrane phospholipids with longer-chain fatty acids to maintain membrane fluidity.
Step-by-step explanation:
The gradual replacement of shorter-chain fatty acids by longer-chain fatty acids in membrane phospholipids is an adaptation to colder environments. In a cold environment, membranes composed largely of saturated fatty acids tend to become less fluid and more susceptible to rupturing. By increasing the proportion of unsaturated fatty acids, the membrane maintains its fluidity, which is crucial for membrane transport.
For example, fish that live in cold environments are capable of changing the proportion of unsaturated fatty acids in their membranes. This allows their membranes to remain fluid and functional even at low temperatures.
Therefore, when a bacterial culture growing at 37∘C is transferred to a culture room maintained at 25∘C, it is likely that the bacterial cells will gradually replace the shorter-chain fatty acids in their membrane phospholipids with longer-chain fatty acids to maintain membrane fluidity.