Chapter 1 — Introduction to Microbiology
Key Concepts Quick Recap
| Scientist | Contribution |
|---|
| Antonie van Leeuwenhoek (1674) | First to observe microorganisms; father of microbiology |
| Louis Pasteur | Disproved spontaneous generation; pasteurisation; germ theory of disease; vaccines |
| Robert Koch | Koch's postulates; discovered TB (Mycobacterium tuberculosis) and cholera bacillus |
| Alexander Fleming (1929) | Discovered penicillin (from Penicillium mould) |
| Edward Jenner (1796) | First vaccination (smallpox using cowpox) |
| Joseph Lister | Antiseptic surgery (carbolic acid) |
I. Choose the Best Answer (MCQs)
1. The "Father of Microbiology" is: (a) Louis Pasteur (b) Robert Koch (c) Antonie van Leeuwenhoek (d) Alexander Fleming
Answer(c) Antonie van Leeuwenhoek
2. Pasteur's swan-neck flask experiment disproved: (a) Germ theory (b) Spontaneous generation (c) Koch's postulates (d) Cell theory
Answer(b) Spontaneous generation Pasteur's experiment: broth in flask with S-shaped neck remained sterile → microbes came from air, not spontaneously generated.
3. Koch's postulates are used to: (a) Culture bacteria (b) Establish the causal relationship between a microorganism and a disease (c) Classify viruses (d) Test antibiotic sensitivity
Answer(b) Establish the causal relationship between a microorganism and a disease
4. Penicillin was discovered by: (a) Louis Pasteur (b) Robert Koch (c) Alexander Fleming (d) Edward Jenner
Answer(c) Alexander Fleming Fleming (1929): observed that Penicillium mould killed Staphylococcus bacteria on a culture plate. Howard Florey and Ernst Chain purified penicillin for clinical use (Nobel Prize 1945).
5. Pasteurisation involves: (a) Boiling at 100°C for 30 min (b) Heating to 62-65°C for 30 min then rapid cooling (c) UV irradiation (d) Chemical sterilisation
Answer(b) Heating to 62-65°C for 30 min then rapid cooling Pasteurisation kills pathogens without completely sterilising the liquid. Used for milk, wine, beer, fruit juices.
6. Which of the following is NOT a microorganism? (a) Bacteria (b) Virus (c) Amoeba (d) Mushroom (large fruiting body)
Answer(d) Mushroom (large fruiting body) Microbiology studies microorganisms: bacteria, viruses, fungi (yeasts and moulds), protozoa, algae, prions. A mature mushroom fruiting body is macroscopic. The mycelium (vegetative part) of mushroom fungi is microscopic.
7. Viruses are obligate intracellular parasites because: (a) They have their own metabolism (b) They can only replicate inside a living host cell (c) They are prokaryotes (d) They produce spores
Answer(b) They can only replicate inside a living host cell Viruses lack ribosomes and metabolic machinery → depend entirely on host cell for replication.
II. Short Answer Questions
Q1. State Koch's postulates and give their significance.
Answer
Koch's four postulates (1876): 1. Pathogenic organism must be present in all cases of the disease. 2. It must be isolated from diseased host and grown in pure culture. 3. Pure culture must cause disease when inoculated into a healthy susceptible host. 4. The organism must be re-isolated from the experimentally infected host and match the original.
Significance: Gold standard for establishing causation of infectious diseases. Still used today for newly emerging diseases. Some limitations: obligate intracellular parasites (viruses, Chlamydia) cannot be grown in pure culture on media.
Q2. Distinguish between prokaryotes and eukaryotes.
Answer
| Feature | Prokaryotes | Eukaryotes |
|---|
| Examples | Bacteria, Archaea | Fungi, Protozoa, Algae, Humans |
| Nucleus | No membrane-bound nucleus; nucleoid | True membrane-bound nucleus |
| Size | 1-10 μm | 10-100 μm |
| Organelles | No membrane-bound organelles | Mitochondria, ER, Golgi, etc. |
| Ribosomes | 70S (30S + 50S) | 80S (40S + 60S) |
| Cell wall | Peptidoglycan (bacteria) | Present in fungi (chitin); absent in animals |
Exam Checklist
- Leeuwenhoek: father of microbiology, first to see bacteria (1674).
- Pasteur: swan-neck flask, pasteurisation, vaccines (cholera, anthrax, rabies), germ theory.
- Koch: Koch's postulates (4 steps), discovered TB and cholera bacilli.
- Fleming: discovered penicillin (1929).
- Jenner: first vaccine (smallpox/cowpox, 1796).
- Prokaryotes: bacteria; no true nucleus, 70S ribosomes.
- Viruses: obligate intracellular parasites; replicate only in host cells.
