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MEDICAL MICROBIOLOGY – SHORT EXAM NOTES
🔬 1. BACTERIAL STRUCTURE & FUNCTION✅
Basic structure✓Cell wall → shape, protection, Gram reaction
✓Cell membrane → transport, respiration, enzyme activity
✓Cytoplasm → metabolic reactions
✓Ribosome (70S) → protein synthesis
✓Nucleoid → bacterial DNA (single circular chromosome)
✅
External structures✓Capsule → virulence, anti-phagocytic
✓Flagella → motility
✓Pili/fimbriae → attachment, conjugation
✓Spore → survival in harsh conditions
📌 Exam key: Capsule = virulence, Ribosome = drug target, Spore = resistance
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2. PLASMID✔ Small extra-chromosomal circular DNA
✔ Replicates independently
✔ Carries antibiotic resistance genes
✔ Can transfer between bacteria
📌 Exam key: plasmid = drug resistance + gene transfer
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3. BACTERIAL GENETICS✔ Mutation
Permanent DNA change
May cause drug resistance
✔ Gene transfer methods
1️⃣ Conjugation
2️⃣ Transformation
3️⃣ Transduction
📌 Exam key: These explain spread of resistance in hospitals
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4. GENE TRANSFER MECHANISMS🧪 Conjugation
✔ DNA transfer via sex pilus
✔ Requires direct cell contact
✔ Often transfers plasmids
📌 Most important for antibiotic resistance
🧪 Transformation
✔ Uptake of free DNA from environment
✔ No cell contact required
📌 Seen in: Pneumococcus, Neisseria
🧪 Transduction
✔ DNA transfer via bacteriophage (virus)
📌 Phage carries DNA from one bacterium to another
🦠 5. BACTERIOPHAGE
✔ Virus that infects bacteria
✔ Injects DNA into bacteria
Types:
Lytic cycle → bacterial destruction
Lysogenic cycle → DNA integrates into host
📌 Exam key: phage = gene transfer + toxin production
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