Q.What are transgenic bacteria? Illustrate using any one example.

Transgenic bacteria are microorganisms whose genetic makeup has been intentionally altered by introducing a foreign gene from another organism. This genetic modification enables the bacteria to express the new gene, leading to the production of a specific protein or the acquisition of a desired trait that it would not naturally possess.

A prominent example is the production of human insulin. Human insulin is a protein hormone composed of two polypeptide chains, A and B, which are linked together. To produce human insulin using genetic engineering, separate DNA sequences corresponding to the A and B chains were introduced into plasmids of Escherichia coli. These modified bacteria then synthesized the A and B chains independently. The individual chains were subsequently extr …

Transgenic bacteria are a remarkable outcome of genetic engineering, representing microorganisms whose genetic material has been intentionally altered by introducing DNA from an external source, often from a different species. The term "transgenic" itself refers to an organism that contains a gene (or genes) from another species, which has been artificially inserted into its genome. In the case of bacteria, this foreign DNA is typically incorporated into their own chromosomal DNA or, more commonly, into a plasmid – a small, circular, extra-chromosomal DNA molecule that can replicate independently.

The primary purpose of creating transgenic bacteria is to harness their rapid growth and efficient protein synthesis machinery to produce specific substances, such as enzymes, hormones, or vaccines, in large quantities. By inserting a gene of interest into a bacterial cell, scientists can essentially reprogram the bacterium to act as a tiny biological factory, churning out the desired product. This process relies heavily on recombinant DNA technology, where specific DNA segments are cut, joined, and introduced into a host organism.

Example: Production of Human Insulin

One of the most significant and widely recognized applications of transgenic bacteria is the large-scale production of human insulin, a vital hormone for individuals with diabetes. Historically, insulin for diabetic patients was extracted from the pancreases of slaughtered animals like pigs and cattle. However, this animal-derived insulin often caused allergic reactions in some patients and faced supply limitations.

The advent of recombinant DNA technology offered a solution:

• Identifying the Gene: Scientists first identified and isolated the gene responsible for producing human insulin. Human insulin is composed of two short polypeptide chains, A and B, which are linked together. In humans, these chains are initially synthesized as a single precursor molecule called pro-insulin, which then undergoes processing to remove a connecting peptide (C-peptide) to form mature insulin.
• Overcoming a Challenge: Bacteria lack the enzymatic machinery to process pro-insulin into mature insulin. To circumvent this, in 1983, the American company Eli Lilly developed a strategy. They prepared two separate DNA sequences corresponding to the A-chain and B-chain of human insulin.
• Insertion into Plasmids: Each of these synthetic DNA sequences (for the A-chain and B-chain) was then separately introduced into different plasmids. These plasmids were designed to carry a gene that would allow for the expression of the insulin chains. …

Method — one-line definition, then trace a single worked example

Definition: an organism ⟶ a bacterium that carries and expresses a foreign gene.

Worked trace (human insulin in E. coli): human insulin gene split into A-chain and B-chain DNA → each ligated into a separate plasmid → plasmids transformed into E. coli → bacteria express and produce chain A and chain B separately → chains p …