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Game plan Lecture Antibiotics Antibiotic resistance Gene transfer Transformation Transduction Conjugation Extra credit assignment Lab Lab Exam Pre-lab Transformation - 1928: Fleming discovered penicillin, produced by Penicillium Discovery of Antimicrobial Drugs Figure 1.5Figure 1.5 Where to antimicrobials come from? Broad spectrum- affect a broad range of gram -positive and gram-negative bacteria Narrow spectrum- affects a narrow range of bacteria Spectrum of activity This bacterium is lysing because an antibiotic disrupted its cell wall. Why doesnt the antibiotic lyse human cells? Pit Stop The Action of Antimicrobial Drugs Figure 20.2 Case study in narrow spectrum antibiotics: Penicillin - Natural penicillins - Semisynthetic penicillins Figure 20.7 Penicillin retention A case study in broad spectrum: Tetracycline Figure 20.11 Resistance to Antibiotics Figure 20.20 1.Enzymatic destruction of drug 2.Prevention of penetration of drug 3.Alteration of drugs target site 4.Rapid ejection of the drug Figure 20.8 A peek at antibiotic resistance penicillinase Figure 20.21 Antibiotic resistance and superinfections - A variety of mutations can lead to antibiotic resistance - Misuse of antibiotics selects for resistance mutants. Misuse includes: lUsing outdated or weakened antibiotics lUsing antibiotics for the common cold and other inappropriate conditions lUsing antibiotics in animal feed lFailing complete the prescribed regimen lUsing someone elses leftover prescription - Resistance genes are often on plasmids or transposons that can be transferred between bacteria Mechanisms of resistance The future of antibiotic resistance NDM-1 - 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 Klebsiella pneumoniae 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 How was NDM-1 tranfered? Vertical gene transfer Horizontal gene transfer All transfer methods rely on recombination Figure 8.22 Horizontal gene transfer: Transformation Demo Horizontal gene transfer: Transformation 1920s- Griffith experiment Horizontal gene transfer: Transformation 1920s- Griffith experiment Horizontal gene transfer: Transformation DNA: -Cell free or “naked” DNA Requirements: -Competent cells -Recombination Horizontal gene transfer: Transduction Demo (generalized, specialized) Horizontal gene transfer: Generalized transduction DNA type: -Small chromosomal fragments from bacteria Requirements: -Lytic phage -Recombination Horizontal gene transfer: Specialized transduction DNA type: -Bacterial chromosome fragment near phage DNA Requirements: -Lysogenic phage -Formation of prophage -Recombination Horizontal gene transfer: Transduction Horizontal gene transfer: Conjugation Demo (F factor) Horizontal gene transfer: Conjugation DNA type: -F plasmid Requirements: -F + cell -F cell -Sex pili/ cell surface molecules Horizontal gene transfer: Hfr Conjugation DNA type: -F