Many modern medicines, such as insulin or growth hormones, are made using genetically engineered bacteria. Bacterial transformation is used to genetically engineer bacteria to produce medicines. It is now one of the most important and widely used techniques in genetics research but it has a controversial past.

The versatility of the genetic code has enabled scientists to transfer DNA between all sorts of organisms. This is mediated by DNA vectors, of which the most frequently used are plasmids. These extrachromosomal loops of DNA naturally occur in bacteria and carry genes that confer a selective advantage to the host. Unfortunately, this can lead to antibiotic resistance and the emergence of “super-bugs” such as MRSA. For genetic engineering, safe plasmids had to be developed. In the early 1970’s, a group of scientists developed the first very useful plasmid for genetic engineering, which was pBR322 (the “B” stands for Bolivar and the “R” for Rodriguez, after the scientists who created it).

Around this time, when gene transfer became possible, scientists were so fearful that they imposed a voluntary moratorium on this research. This began in 1974 with the “Berg letter” from Paul Berg and other eminent scientists to the science journals, Nature and Science. The voluntary moratorium was in place until 1976 when safety guidelines were produced for conducting such experiments.

Today, bacterial transformation is one of the most widely carried out procedures in molecular biology.