MBBS Microbiology Syllabus

Microbiology syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Microbiology in MBBS, not a summary of it.

1. 1

   General Microbiology

   5 topics

   • Introduction to Microbiology
     • Historical perspective
     • Scope and significance of microbiology
   • Microbial Classification
     • Bacteria
     • Viruses
     • Fungi
     • Protozoa
     • Helminths
   • Microbial Structure
     • Cell morphology
     • Structure
     • Function
   • Microbial Growth and Nutrition
     • Growth requirements
     • Culture media
     • Methods of microbial cultivation
   • Sterilization and Disinfection
     • Physical methods of microbial control
     • Chemical methods of microbial control
2. 2

   Bacteriology

   6 topics

   • Bacterial morphology
     • Shapes
     • Arrangements
     • Staining characteristics
   • Bacterial genetics
     • Plasmids
     • Transposons
     • Bacterial conjugation
     • Transformation
     • Transduction
   • Bacterial metabolism
     • Aerobic and anaerobic respiration
     • Fermentation
     • Metabolic pathways
   • Bacterial pathogenesis
     • Virulence factors
     • Mechanisms of pathogenicity
     • Host defense mechanisms
   • Clinical microbiology
     • Laboratory diagnosis of bacterial infections
     • Culture techniques
     • Antibiotic susceptibility testing
   • Important bacterial pathogens
     • Gram-positive and gram-negative bacteria causing respiratory infections
     • Gram-positive and gram-negative bacteria causing gastrointestinal infections
     • Gram-positive and gram-negative bacteria causing urinary infections
     • Gram-positive and gram-negative bacteria causing other infections
3. 3

   Viral structure

   1 topic

   • Classification, morphology, and composition of viruses
4. 4

   Fungal morphology

   1 topic

   • Yeasts, molds, and dimorphic fungi
5. 5

   Parasite classification

   1 topic

   • Protozoa and helminths
6. 6

   Immune system components

   1 topic

   • Innate immunity and adaptive immunity

Microbiology flashcards for MBBS

24 of 51 cards from the Microbiology deck — real questions with worked answers.

1. What is microbiology, and who is regarded as the 'Father of Microbiology'?

   Microbiology is the study of microorganisms (bacteria, viruses, fungi, protozoa, helminths, and prions). Antonie van Leeuwenhoek is regarded as the Father of Microbiology for first observing 'animalcules' using his microscopes.

2. State Koch's postulates for establishing that a microbe causes a disease.

   1) The organism is found in all cases of the disease but not in healthy hosts. 2) It can be isolated and grown in pure culture. 3) Inoculation of the pure culture into a susceptible host reproduces the disease. 4) The same organism is re-isolated from the experimentally infected host.

3. Which three domains make up the modern (Woese) classification of life, and which contain prokaryotes?

   The three domains are Bacteria, Archaea, and Eukarya. Bacteria and Archaea are prokaryotes; Eukarya are eukaryotes. The classification is based on 16S/18S ribosomal RNA sequence comparison.

4. What is binomial nomenclature, and how is a bacterial species name written?

   Binomial nomenclature (Linnaeus) names organisms by Genus + species. The genus is capitalized, the species is lowercase, and both are italicized (or underlined), e.g. Staphylococcus aureus, abbreviated S. aureus.

5. Compare prokaryotic and eukaryotic cells in terms of nucleus, ribosomes, and organelles.

   Prokaryotes: no membrane-bound nucleus (nucleoid), 70S ribosomes ($30S + 50S$), no membrane-bound organelles. Eukaryotes: true membrane-bound nucleus, 80S ribosomes ($40S + 60S$), and membrane-bound organelles (mitochondria, ER, Golgi).

6. Describe the structure and chemical composition of bacterial peptidoglycan (murein).

   Peptidoglycan is a mesh polymer of alternating $N$-acetylglucosamine (NAG) and $N$-acetylmuramic acid (NAM) linked by $\beta\text{-}1,4$ glycosidic bonds, with NAM cross-linked by short peptide chains (e.g. via D-Ala–D-Ala). It provides cell wall rigidity and osmotic protection.

7. Differentiate Gram-positive and Gram-negative cell walls.

   Gram-positive: thick peptidoglycan layer with teichoic/lipoteichoic acids, no outer membrane; stains purple. Gram-negative: thin peptidoglycan, an outer membrane containing lipopolysaccharide (LPS/endotoxin), and a periplasmic space; stains pink/red.

8. Outline the steps of the Gram stain and the role of each reagent.

   1) Crystal violet (primary stain – all cells purple). 2) Gram's iodine (mordant – forms crystal violet–iodine complex). 3) Alcohol/acetone (decolorizer – removes complex from Gram-negative cells). 4) Safranin (counterstain – Gram-negative cells turn pink). Gram-positive retain purple.

9. What is the function and key feature of bacterial endospores?

   Endospores are dormant, highly resistant survival structures (formed by Bacillus and Clostridium) that resist heat, desiccation, radiation, and chemicals. They contain dipicolinic acid and calcium, and small acid-soluble proteins protecting DNA; they germinate when conditions improve.

10. Distinguish bacterial flagella, fimbriae (pili), and the capsule by function.

    Flagella: locomotion (motility). Fimbriae/pili: adhesion to surfaces; sex pilus mediates conjugation/DNA transfer. Capsule: a polysaccharide layer providing antiphagocytic protection and a virulence factor.

11. Define the four bacterial growth phases on a growth curve.

    1) Lag phase – adaptation, no division. 2) Log/exponential phase – maximum constant doubling. 3) Stationary phase – growth equals death (nutrient depletion). 4) Death/decline phase – exponential decline in viable cells.

12. Give the formula for the number of bacterial cells after $n$ generations starting from $N_0$ cells, and relate $n$ to time.

    $$N = N_0 \times 2^{n}$$ where $n$ is the number of generations. If $g$ is the generation (doubling) time and $t$ is elapsed time, then $n = \dfrac{t}{g}$.

13. How is bacterial generation (doubling) time $g$ calculated from cell counts over time $t$?

    $$g = \frac{t}{n} = \frac{t \,\log 2}{\log N - \log N_0} = \frac{t}{3.3\,(\log N - \log N_0)}$$ where the factor $3.3 = 1/\log_{10} 2$.

14. Classify bacteria by oxygen requirement.

    Obligate aerobes (require $\ce{O2}$), obligate anaerobes (killed by $\ce{O2}$), facultative anaerobes (grow with or without $\ce{O2}$, prefer it), microaerophiles (need low $\ce{O2}$), and aerotolerant anaerobes (tolerate but don't use $\ce{O2}$).

15. Classify bacteria by optimal growth temperature.

    Psychrophiles (optimum near $15\,^{\circ}\text{C}$), mesophiles (optimum $\sim 37\,^{\circ}\text{C}$, most human pathogens), thermophiles (optimum $50\text{–}60\,^{\circ}\text{C}$), and hyperthermophiles (optimum $>80\,^{\circ}\text{C}$).

16. Define the nutritional categories: photoautotroph, chemoautotroph, photoheterotroph, chemoheterotroph.

    Energy source (photo = light, chemo = chemical) plus carbon source (auto = $\ce{CO2}$, hetero = organic carbon). Photoautotroph: light + $\ce{CO2}$. Chemoautotroph: chemicals + $\ce{CO2}$. Photoheterotroph: light + organic C. Chemoheterotroph: chemicals + organic C (most pathogens).

17. Distinguish sterilization, disinfection, and antisepsis.

    Sterilization: complete destruction/removal of ALL microorganisms including spores. Disinfection: elimination of most pathogens (not necessarily spores) from inanimate objects. Antisepsis: reduction of microbes on living tissue/skin.

18. What are the standard conditions for moist-heat sterilization in an autoclave?

    An autoclave uses saturated steam under pressure: $121\,^{\circ}\text{C}$ at $15\ \text{psi}$ ($\approx 103\ \text{kPa}$) for $15\text{–}20$ minutes. Moist heat kills by denaturing/coagulating proteins.

19. What temperature/time defines hot-air oven (dry heat) sterilization, and how does dry heat kill?

    Hot-air oven: $160\,^{\circ}\text{C}$ for $1\text{–}2$ hours (or $170\,^{\circ}\text{C}$ for 1 hour). Dry heat kills by oxidation and denaturation; it is used for glassware, powders, and oils.

20. Define the D-value and Z-value in microbial death kinetics.

    D-value (decimal reduction time): time at a given temperature to kill $90\%$ ($1\log_{10}$) of the population. Z-value: the temperature increase ($^{\circ}\text{C}$) needed to reduce the D-value tenfold. Microbial death follows first-order (logarithmic) kinetics.

21. What is pasteurization, and give the two common protocols?

    Pasteurization reduces pathogen load (not sterilization) in liquids like milk. Holder method: $63\,^{\circ}\text{C}$ for 30 min. Flash/HTST: $72\,^{\circ}\text{C}$ for 15 s. (UHT: $\sim 140\,^{\circ}\text{C}$ for a few seconds.)

22. Name the basic bacterial morphologies (shapes) and one arrangement term for cocci.

    Cocci (spheres), bacilli (rods), spirilla/spirochetes (spirals), vibrios (comma-shaped), coccobacilli. Coccal arrangements include diplococci (pairs), streptococci (chains), and staphylococci (clusters).

23. What is acid-fast staining used for, and what makes a cell acid-fast?

    Acid-fast (Ziehl-Neelsen) staining identifies Mycobacterium and Nocardia. Their cell walls contain mycolic acids (long-chain fatty acids/waxes) that resist decolorization by acid-alcohol, so they retain carbol fuchsin (red); the background counterstains blue.

24. Compare the three mechanisms of horizontal gene transfer in bacteria.

    Transformation: uptake of naked/free DNA from the environment. Transduction: DNA transfer via a bacteriophage vector. Conjugation: direct cell-to-cell DNA transfer through a sex pilus (often plasmid-mediated, e.g. F factor).

See more Microbiology flashcards →

Planning Microbiology for MBBS

Microbiology (MBBS) FAQ