Question

Which of the following processes will most likely occur when you transfer a bacterial culture from 37 degree C to 10 degree C?

a) the bacteria will start synthesizing cholesterol

b) the bacteria will remove cholesterol from their membranes

c) the bacteria will reduce the number of unsaturated bonds in the fatty acid tails of their phospholipids

d) the bacteria will increase the synthesis of phospholipids with very long fatty acid tails and insert these into their membranes

e) the bacteria will increase the synthesis of phospholipids with unsaturated fatty acid tails and insert these into their membranes

Answer 1

Bacteria cell membranes lack cholesterol and cannot synthesize it. However, they can degrade cholesterol. Bacteria have hoponoids instead of membrane sterols like cholesterol..Bacteria adapt to high temperature by synthesizing saturated long chain fatty acids.

The shift of bacterial culture to the lower temperature decreases membrane fluidity as hydrophobic chains are incorporated due to van der Waals interaction. In order to compensate for decreased membrane fluidity at low temperature, bacteria synthesize unsaturated fatty acids. Cis double bonds are present in unsaturated fatty acids while saturated fatty acids have carbons that are joined by single bonds. Phospholipids with unsaturated fatty acid tails are synthesized in order to prevent decreased membrane fluidity. These phospholipids synthesized at low tempertaure by the bacteria have shorter chains and more cis double bonds. The short chains will decrease van der Waals interactions while the cis double bonds will prevent the fatty acids tails packing due to kinks in structure. Kinks are produced which prevent rotation of the double bond. Cis bonds have hydrogen present on same side of the molecule.

Option e.