Q.Alexander Fleming discovered penicillin while working on which of the following bacteria?
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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.
Antibiotics are effective only against bacteria, not against viruses (like the common cold or flu). Taking an antibiotic for a viral infection is useless and contributes to a serious problem called antibiotic resistance — where bacteria evolve to become immune to the drug.
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. …
Alexander Fleming's accidental discovery of penicillin in 1928 happened while he was culturing a particular bacterium whose growth was inhibited by a contaminating mould. …
Alexander Fleming discovered penicillin while working with Staphylococcus bacteria.
In 1928, Alexander Fleming was culturing Staphylococcus bacteria when one of his culture plates became contaminated by the mould Penicillium notatum. He noticed that the Staphylococci around the mould had been killed/inhibited, and the substance responsible was named penicillin …
Showing the 12 most recent of 15 on this concept.
- CBSE 2026Set ANNUAL1 markQ.Alexander Fleming, Ernst Chain and Howard Florey were awarded the Nobel Prize in 1945 for the discovery of _________.
›Reveal solutionSolution
The blank is penicillin — the antibiotic from the mould Penicillium notatum whose discovery earned Fleming, Chain and Florey the 1945 Nobel Prize.
In the CBSE/NCERT Microbes in Human Welfare chapter, Alexander Fleming accidentally noticed that the mould Penicillium notatum killed Staphylococcus bacteria in a culture plate. Ernst Chain and Howard …
- CBSE 2025Set A1 markMCQQ.First antibiotic is obtained from which micro organism?(a) Penicillium(b) Streptococcus(c) Salmonella typhimurium(d) Vibrio cholerae
›Reveal solutionSolution
Penicillin, the first antibiotic, was obtained from the fungus Penicillium.
In 1929, Alexander Fleming observed that a mould contaminating his bacterial culture plate (Staphylococcus) had inhibited bacterial growth around it. The mould was identified as Penicillium notatum, and the antibacterial substance it secreted was named penicillin — the world's first antibiotic. It was later mass-produced by Er …
- CBSE 2025Set ANNUAL1 markQ.Who discovered the first antibiotic? Name the antibiotic.
›Reveal solutionSolution
Alexander Fleming discovered Penicillin, the first antibiotic, in 1928, after noticing that a mould contaminating one of his bacterial culture plates had killed the surrounding bacteria.
While working with Staphylococcus cultures, Fleming observed that a plate accidentally contaminated with the mould Penicillium notatum showed a clear zone around the mould where the bacteria had failed to grow. He deduced that the mould was releasing a substance that inhibited/killed the bacteria, which he named penicillin. Its therapeutic potential was later fully realised and the antibiotic was purifi …
- CBSE 2024Set E1 markMCQQ.Alexander Fleming discovered penicillin while working on which of the following bacteria?(a) Streptococcus(b) Acetobacter(c) Staphylococcus(d) Lactobacillus
›Reveal solutionSolution
Alexander Fleming discovered penicillin while working with Staphylococcus bacteria.
In 1928, Alexander Fleming was culturing Staphylococcus bacteria when one of his culture plates became contaminated by the mould Penicillium notatum. He noticed that the Staphylococci around the mould had been killed/inhibited, and the substance responsible was named penicillin …
- CBSE 2024Set BOTANY1 markQ.Correct the statement, if necessary, by changing the underlined word(s) only: The first antibiotic discovered by Alexander Fleming is chloromycetin.
›Reveal solutionSolution
Fleming's discovery was penicillin; chloromycetin (chloramphenicol) is a different, later antibiotic.
In 1928, Alexander Fleming observed that a mould contaminating his bacterial culture plate, later identified as Penicillium notatum, inhibited the growth of Staphylococcus bacteria around it. The active substance he isolated was named penicillin — the first antibiotic ever discovered, though its full therapeutic potential was only realised and mass-produced later by Ernst Chain and Howard Florey. C …
- CBSE 2023Set A1 markQ.Match the columns. Column A item: Penicillin. Choose the matching term from Column B:(a) First antibiotic(b) Recessive gene blood disease(c) Zoological parks(d) Absence of 1 X-chromosome(e) Separation of DNA fragments(f) Amoebiasis(g) Attached DNA fragments(h) Adaptation
›Reveal solutionSolution
Penicillin, discovered by Alexander Fleming from the fungus Penicillium notatum, was the first antibiotic to be discovered.
In 1928, Alexander Fleming observed that a mould contaminating his bacterial culture plate (later identified as Penicillium notatum) inhibited the growth of the surrounding Staphylococcus bacteria. The active antibacterial substance was named penicillin, and it became th …
- CBSE 2022Set HE2201 markQ.Fill in the blank: An antibiotic called penicillin is obtained from a ______ fungus.
›Reveal solutionSolution
Penicillin, the first antibiotic, is produced by the blue-green mould Penicillium.
In 1928, Alexander Fleming accidentally observed that a mould contaminating a bacterial culture plate had killed the surrounding Staphylococcus colonies. He identified the mould as Penicillium notatum and named the antibacterial substance it secreted "penicillin." It works by inhibiting the synthesis of the bacterial cell wall, causing the bacterial cell to burst (lyse). Ernst Chain and Howard Florey later purified it and made it usable as a drug, …
- CBSE 2022Set ANNUAL1 markQ.The first antibiotic discovered was _______.
›Reveal solutionSolution
Penicillin, discovered by Alexander Fleming from the mould Penicillium notatum, was the first antibiotic to be discovered.
In 1928, Alexander Fleming noticed that a Petri dish culture of Staphylococcus bacteria he had accidentally left uncovered had been contaminated by a mould, and bacterial growth was inhibited in a clear zone around the mould colony. He identified the mould as Penicillium notatum and the antibacterial substance it secreted as penicillin — the first antibiotic ever discovered. It was later mass-produced and used c …
- CBSE 2021Set ANNUAL1 markQ.From which micro-organism penicillin is obtained?
›Reveal solutionSolution
Penicillin, the first antibiotic discovered, is produced by the fungus Penicillium.
In 1928, Alexander Fleming observed that a mould growing on a bacterial culture plate inhibited the growth of the surrounding Staphylococcus bacteria. This mould was identified as Penicillium notatum, and the antibacterial substance it secreted was named penicillin.
- Penicillin works by inhibiting bacterial cell wall synthesis, killing actively growing bacteria (bactericidal). …
- CBSE 2021Set OC_BOTANY1 markMCQQ.Penicillin—an antibiotic is obtained from(a) algae(b) fungus(c) bacteria(d) yeast
›Reveal solutionSolution
Penicillin is a classic example of an antibiotic obtained from a fungus, produced industrially by large-scale fermentation.
Discovery and source
Alexander Fleming accidentally discovered penicillin in 1928 when he noticed that a mould contaminating his Staphylococcus bacterial culture plate had inhibited bacterial growth around it. The mould was identified as Penicillium notatum, a filamentous fungus. Ernst Chain and Howard Florey later purified the active compound and demonstrated its clinical use as an antibiotic.
Industrial production
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- CBSE 2020Set HE8241 markMCQQ.Choose the correct option: Kingdom Fungi reproduces asexually by:(a) Fission(b) Budding(c) Gemmule(d) Conidia
›Reveal solutionSolution
Kingdom Fungi reproduces asexually mainly through spores; the characteristic fungal asexual spore among the given options is the conidium — option (d).
Note on syllabus: Kingdom Fungi and its classification is taught in the Class-11 chapter 'Biological Classification', which is outside MP's current Class-12 rationalised Biology syllabus. It is answered here for completeness.
Fungi reproduce by vegetative means (fragmentation, fission, budding), asexually (via spores) and sexually (via gametes/fusion of hyphae). Looking at the four options:
- Fission — typical of bacteria/some protists, not the characteristic fungal mode.
- Budding — occurs in yeast, but yeast is only one specific fungus, not fungi in general. …
- CBSE 2020Set ANNUAL1 markQ.Write the scientific name of the fungus which produce cyclosporin A.
›Reveal solutionSolution
The immunosuppressant cyclosporin A is obtained from the fungus Trichoderma polysporum.
Concept. Several microbes are exploited to make bioactive molecules of medical importance. Cyclosporin A is a bioactive molecule used as an immunosuppressive agent in organ-transplant patients, because it suppresses the immune response that would otherwise reject the transplanted organ.
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