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Game plan

Game plan. Lecture Antibiotics Antibiotic resistance Gene transfer Transformation Transduction Conjugation. Lab Lab Exam Pre-lab Transformation. Discovery of Antimicrobial Drugs. - 1928 : Fleming discovered penicillin, produced by Penicillium. Figure 1.5.

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Game plan

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  1. Game plan Lecture Antibiotics Antibiotic resistance Gene transfer Transformation Transduction Conjugation Lab Lab Exam Pre-lab Transformation

  2. Discovery of Antimicrobial Drugs - 1928: Fleming discovered penicillin, produced by Penicillium Figure 1.5

  3. Where to antimicrobials come from?

  4. Spectrum of activity Broad spectrum- affect a broad range of gram-positive and gram-negative bacteria Narrow spectrum- affects a narrow range of bacteria

  5. Pit Stop This bacterium is lysing because an antibiotic disrupted its cell wall. Why doesn’t the antibiotic lyse human cells?

  6. The Action of Antimicrobial Drugs Figure 20.2

  7. Case study in narrow spectrum antibiotics: Penicillin http://ihm.nlm.nih.gov/images/A20824

  8. Case study in narrow spectrum antibiotics: Penicillin • - Natural penicillins • - Semisyntheticpenicillins

  9. Penicillin prevents cross-linking in cell wall

  10. A peek at antibiotic resistance… penicillinase Figure 20.8

  11. Resistance to Antibiotics • Enzymatic destruction of drug • Prevention of penetration of drug • Alteration of drug's target site • Rapid ejection of the drug Figure 20.20

  12. Mechanisms of resistance • - A variety of mutations can lead to antibiotic resistance • - Misuse of antibiotics selects for resistance mutants. Misuse includes: • Using outdated or weakened antibiotics • Using antibiotics for the common cold and other inappropriate conditions • Using antibiotics in animal feed • Failing complete the prescribed regimen • Using someone else's leftover prescription • - Resistance genes are often on plasmids or transposons that can be transferred between bacteria

  13. The future of antibiotic resistance… carbapenem-resistant Enterobacteriaceae • - CREs- Resistant to all antibiotics except colistin (affects membranes) and tigecycline (protein synthesis inhibitor ~ tetracylcine) • - One CRE: NDM-1 • New Delhi metallo-beta-lactamase gene confers resistance to all antibiotics except colistin (affects membranes) and tigecycline (protein synthesis inhibitor ~ tetracylcine) • Originally identified in December 2009 in Klebsiellapneumoniae • from patient in New Delhi, India • Currently found in K. pneumonia, E. coli, and Enterobacteriaceae • in India, Pakistan, the United Kingdom, the United States, • Canada, and Japan

  14. How genes like NDM-1 transferred? Horizontal gene transfer Vertical gene transfer

  15. All transfer methods rely on recombination Figure 8.22

  16. Horizontal gene transfer: Transformation Demo

  17. Horizontal gene transfer: Transformation 1920s- Griffith experiment

  18. Horizontal gene transfer: Transformation 1920s- Griffith experiment

  19. Horizontal gene transfer: Transformation DNA: • Cell free or “naked” DNA Requirements: • Competent cells • Recombination

  20. Horizontal gene transfer: Transduction Demo (generalized, specialized)

  21. Horizontal gene transfer: Generalized transduction DNA type: • Small chromosomal fragments from bacteria Requirements: • Lytic phage • Recombination

  22. Horizontal gene transfer: Specialized transduction DNA type: • Bacterial chromosome fragment near phage DNA Requirements: • Lysogenic phage • Formation of prophage • Recombination

  23. Horizontal gene transfer: Transduction

  24. Horizontal gene transfer: Conjugation Demo (F factor)

  25. Horizontal gene transfer: Conjugation DNA type: • F plasmid Requirements: • F + cell • F – cell • Sex pili/ cell surface molecules

  26. Horizontal gene transfer: Hfr Conjugation DNA type: • F plasmid/ bacterial chromosome Requirements: • Hfr cell • F – cell • Sex pili/ cell surface molecules

  27. Horizontal gene transfer compared

  28. Independent Study Study for Exam 2!

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