Bacteria Can Produce Insulin When Genetically Engineered

Insulin is a hormone that regulates metabolism by promoting the absorption of glucose from the blood into cells. When the body does not produce enough insulin or cannot use it effectively, a condition known as diabetes mellitus can arise. This leads to high blood sugar levels and can cause long-term complications, including damage to the nervous system, eyes, and kidneys.

Before the 1980s, the primary source of insulin for therapeutic use was the pancreases of cattle and pigs. This process was inefficient, requiring a large number of animal pancreases to produce a small amount of insulin. While animal-derived insulin saved millions of lives, some patients experienced allergic reactions due to impurities and structural differences between animal and human insulin. These challenges created a need for a more reliable and purer source.

Unlocking Insulin Production: The Role of Genetic Engineering

Bacteria do not naturally produce human insulin; they acquire this ability only when modified through genetic engineering. This technological shift, which began in the late 1970s, addressed the limitations of animal-sourced insulin. The process is an application of recombinant DNA technology, which combines genetic material from different sources. It begins with isolating the human gene responsible for producing insulin, which contains the precise code for building the protein.

Once isolated, the human insulin gene is inserted into a small, circular piece of bacterial DNA called a plasmid. This plasmid acts as a vector to carry the foreign gene into a host organism. Scientists use specific enzymes to cut open the plasmid and splice the human gene into it, creating what is known as a recombinant plasmid.

The final step is introducing this recombinant plasmid into a host bacterium, most commonly a laboratory strain of Escherichia coli (E. coli). This is achieved through a process called transformation, where bacteria are treated to make their cell membranes more permeable, allowing them to take up the plasmids. Once inside, the recombinant plasmid becomes a part of the bacterium’s genetic library, ready to be used by the cell’s machinery.

How Engineered Bacteria Synthesize Human Insulin

Inside the engineered bacterium, insulin production relies on the cell’s natural protein-making processes. The bacterial machinery recognizes the inserted human gene and begins to read its genetic code. This first step, called transcription, creates a messenger RNA (mRNA) molecule, which is a temporary copy of the gene’s instructions. The mRNA then travels to the bacterium’s ribosomes, the cellular factories for protein synthesis.

At the ribosome, the process of translation occurs. The ribosome reads the mRNA sequence and assembles amino acids in the specific order dictated by the human insulin gene. This results in the creation of proinsulin, a precursor to active insulin.

Proinsulin is a single polypeptide chain that is folded and then cleaved by enzymes to form the two separate chains (A and B) that constitute the mature insulin molecule. The bacterium effectively becomes a miniature factory, using the inserted human gene as a blueprint to synthesize a protein that is identical to the one produced in the human pancreas.

Industrial Scale-Up: From Bacterial Cultures to Lifesaving Medicine

Once a strain of bacteria capable of producing human insulin is developed, the process is scaled up for mass production. This involves growing vast quantities of the engineered bacteria in large, controlled environments called fermenters or bioreactors. These large tanks hold thousands of gallons of a nutrient-rich culture medium, providing ideal conditions for bacterial growth and insulin production.

Inside the fermenter, parameters such as temperature, pH, oxygen levels, and nutrient supply are precisely controlled to maximize the yield of insulin. The bacteria multiply rapidly, continuously producing the human insulin protein as directed by the recombinant plasmid. After the fermentation cycle is complete, the bacterial cells are harvested from the culture medium.

The subsequent steps involve breaking open the bacterial cells to release the insulin and then subjecting the mixture to a purification process. This multi-stage procedure is designed to separate the insulin from bacterial proteins and other cellular components. Techniques such as chromatography are used to isolate the insulin with a high degree of purity. Quality control tests are performed to ensure the final product is safe, effective, and free of contaminants.

The Revolution of Bacterially Derived Insulin

The introduction of bacterially derived human insulin, first approved for medical use in 1982, marked a turning point in diabetes management. This innovation solved the supply issues associated with animal-sourced insulin, making the medication more widely available to patients. The consistency of the production process also ensured a stable and reliable supply chain.

One of the primary benefits was the improved purity and safety of the insulin. Because it is structurally identical to the hormone produced by the human body, bacterially derived insulin reduced the incidence of allergic reactions seen with animal insulins. This higher purity meant fewer side effects and better tolerance for patients.

This technological advancement also offered ethical advantages by eliminating the reliance on animals. Producing vast quantities of insulin from bacterial cultures is a more sustainable and humane approach to manufacturing. The development of genetically engineered insulin transformed diabetes care, providing a safer, more reliable, and consistent therapeutic option that has improved the quality of life for millions worldwide.