Let’s start with something you already know. You have seen how a baker uses yeast to make bread rise, or how curd is made by adding a spoonful of old curd to warm milk. In both cases, a living microbe does the work. Now imagine that you could take that same yeast or bacterium and give it a new instruction — a new piece of genetic code — so that it starts making something it never made before. That is the core idea behind a transgenic bacterium.
A transgenic bacterium is a bacterium whose DNA has been deliberately altered by adding a gene from another organism. The word “transgenic” simply means “across genes” — a gene has been moved from one species into another. Because bacteria reproduce very fast and are easy to grow in large tanks, they become tiny living factories. You give them the blueprint (the gene), and they churn out the product.
The classic NCERT example: Human insulin from E. coli
Before the 1980s, people with diabetes were given insulin extracted from the pancreases of cows or pigs. That animal insulin worked, but it was slightly different from human insulin and sometimes caused allergic reactions. Scientists wanted a way to make exactly human insulin in large amounts.
Here is what they did, step by step:
- They identified the human gene that carries the instructions for making insulin.
- They cut out that gene and inserted it into a small circular piece of bacterial DNA called a plasmid.
- They put this modified plasmid back into a common bacterium, Escherichia coli (E. coli).
- When the E. coli multiplied, every new bacterium carried the human insulin gene. And because the bacterium’s own machinery reads DNA the same way human cells do, it began producing human insulin protein.
That E. coli is now a transgenic bacterium — it contains a gene from a different species (human) and expresses it.
The key point is not the science of how the gene is inserted. The key point is that a living microbe has been given a new trait from another species, and that trait is inherited by all its offspring. This is what makes it “transgenic” — the new gene becomes a permanent part of the bacterium’s genetic makeup.
Why does this matter for a commerce or humanities student?
You might never work in a lab, but you will encounter the products of transgenic bacteria every day. Here are the most important ones from your NCERT syllabus:
- Human insulin (Humulin) — the first genetically engineered product approved for human use. It is safer and more reliable than animal insulin.
- Human growth hormone — used to treat children with growth disorders. Before transgenic bacteria, it had to be extracted from human cadavers, which was risky.
- Vaccines — the hepatitis B vaccine is made using a transgenic yeast (a similar principle). The gene for the virus’s surface protein is put into yeast, which then produces the protein. That protein is purified and used as the vaccine.
- Enzymes — laundry detergents often contain enzymes made by transgenic bacteria. These enzymes break down stains at lower temperatures, saving energy.
- Bioremediation — some transgenic bacteria are designed to eat oil spills or break down plastic waste. They have genes from other bacteria that can digest hydrocarbons.
In your NCERT textbook (Class 12 Biology, Chapter 12: Biotechnology and its Applications), the insulin example is the central case study. The textbook states that E. coli was transformed with the human insulin gene, and the resulting bacteria produced insulin in fermentation tanks. This is the only example you need to remember for exams.
A simple way to remember it …