The first choice for the expression of recombinant proteins is typically E. coli. Production of proteins in this bacterial strain is well-established, fast and simple and usually provides high yields. Recent progress in the fundamental understanding of transcription, translation, and protein folding in E. coli, improved genetic tools had made this bacterium more valuable than ever for the expression of complex eukaryotic proteins. How much do you know about protein expression in bacteria?
Reference: Protein Expression in Bacteria