Question

How do the bacteria and fungi which can grow at different temperature adapt to changes in membrane fluidity?

Answer 1

Membrane lipids should be in such a way that in hot weather it should not be too fluid so that it will melt away or in cold it should not be too rigid that the membrane will break.

In order to maintain an optimum membrane fluidity in different temperatures the composition of membrane lipids are changed. The lipid composition depends on the length of the hydrocarbon chain and the degree of saturation.

Saturated fatty acids will have only single bonds while unsaturated fatty acids have double bonds and triple bonds in the hydrocarbon chain.

Unsaturated fattyacids (lipids) thus are of lower melting point( will remain fluid at lower temperature) and will not freeze as fast as saturated fatty acids.

Short and branched chain fatty acids have higher melting point compared to long unbranched chain

So in cold weather membrane should not freeze and be rigid, so fatty acids with lower melting point is preferred. Thus the organisms in cold weather will have more unsaturated, short , branched chain fatty acids in their membrane.

While for hot weather higher melting point fatty acid is preferred, so that the membrane will not be too fluid. So the organisms in hot weather will have more saturated, long,unbranched fatty acids in their membrane.