How does gene expression level contribute to thermophilic adaptation of prokaryotes? An exploration based on predictors.

By analyzing the predicted gene expression levels of 33 prokaryotes with living temperature span from <10 degrees C to >100 degrees C, a universal positive correlation was found between the percentage of predicted highly expressed genes and the organisms' optimal growth temperature. A physical interpretation of the correlation revealed that highly expressed genes are statistically more thermostable than lowly expressed genes. These findings show the possibility of the significant contribution of gene expression level to the prokaryotic thermal adaptation and provide evidence for the translational selection pressure on the thermostability of natural proteins during evolution.