Question

Explain what evolutionary adaptations, in general, exist in hyperthermophilic bacteria in terms of their cell membranes and cellular proteins. Your answer should explain how such adaptations provide advantages in terms of protein and membrane function at extremely high temperatures.

Answer 1

The hyperthermophiles live in extreme high temperature and their adaptations include adaptations of enzyme activity, adaptations of protein synthesis and adaptations of composition of membrane lipid. The lipid membrane consists of more saturated and straight chain fatty acids thus maintaining the fluidity of the membrane at high temperature. The phospholipid bilayers have ether linkages (isopreoid diether or tetraether structures) compared to ester linkages in other eukaryotic organisms and bacteria. Many species contain a paracrystalline surface layer which acts as an external barrier against high temperature. There are histone like proteins which bind to DNA and protect it from high temperature. Heat shock proteins and chaperones play an important role in stabilizing the proteins once they get denatured. A reverse gyrase causing positive supercoiling stabilize the DNA. The proteins have higher number of hydrogen bonds with high G and C content , higher number of salt bridges higher thermophilic amin acids like proline, arginine and low lysine.