Overview on the expression of toxic gene products in Escherichia coli

Despite the development of various nonbacterial expression systems, Escherichia coli (E. coli) remains the host of choice for recombinant protein expression. Its culture is simple, fast, inexpensive, and highly efficient (tens of milligrams of pure proteins are typically obtained within 48 hours using as little as 1 liter of culture). Unfortunately, many toxic genes (from various organisms) severely interfere with the physiology of E. coli. As a result, expression yields are dramatically diminished, and sometimes abolished. In fact, some genes are so toxic that E. coli cannot maintain their expression vector during the growth phase (the phase during which recombinant gene expression is presumably repressed). Therefore, modified expression vectors, modified E. coli strains, and appropriate cultivation protocols are needed. This overview discusses several special strategies successfully used to express toxic genes in E. coli.