Q.Name an immunosuppressive agent. From where is it obtained?

Imagine you have a wound that gets infected. Before the 20th century, that infection could easily kill you. Today, we have a weapon against such bacterial infections: antibiotics. The most famous antibiotic, penicillin, comes from a humble source — a fungus.

The intuition is simple: in nature, fungi and bacteria are rivals. They compete for the same food and space. To win this battle, some fungi have evolved a chemical weapon. They produce a substance that kills bacteria or stops them from growing. That substance is an antibiotic. So, an antibiotic-producing fungus is simply a fungus that manufactures a natural chemical to destroy or weaken bacteria.

The precise meaning is this: certain species of fungi (like Penicillium notatum or Cephalosporium acremonium) secrete secondary metabolites — chemicals not essential for their own growth — that are toxic to bacteria. These chemicals interfere with a bacterium's cell wall, its protein-making machinery, or its DNA replication. Because bacterial cells are structurally different from human cells, the antibiotic can often kill the invader without harming us.

Why does this matter? It is the foundation of modern medicine. The discovery of penicillin by Alexander Fleming in 1928 was a turning point. Before antibiotics, a simple scratch could lead to sepsis. Today, antibiotics from fungi save millions of lives every year. They are used to treat pneumonia, tuberculosis, wound infections, and many other bacterial diseases.

Here are the key points to remember:

• Source: The most famous antibiotic-producing fungus is Penicillium, which gives us penicillin. Another is Cephalosporium, which produces cephalosporins. …