Exam 1: Mon 1-27-14; picture ID!Q+A: Friday TBA: bring explanations TODAY1. Archae + Bacteria: Qs2. Antibiotic resistanceBackground + case QsPART IV: Apply to EvolutionAntibiotics- Natural source: several species of bacteria and fungiAlexander Fleming discovered activity of antibiotics by accident in 1928: - Penicillium mold produces penicillin that kills bacteria- Awarded Nobel Prize in 1945- Growth of bacteria Staphylococcus aureus is inhibited in the area surrounding the invading penicillin-secreting Penicillium mold colonyHow Penicillin Works- Rod-shaped bacteria- Membrane, cell wall, & capsule- Cell walls made of peptidoglycan scaffold- Asexual reproduction; have to replicate really fast- Attack the cell wall assembly of pathogenic (disease-causing) bacteria- As a result no more cell walls can be assembled and cells can’t divide Penicillin inhibits peptidoglycan synthesis: which prokaryotes should thus be most vulnerable to penicillin?A all bacteria equally D gram-negative bacteriaB Archae E gram-positive bacteriaC Eubacteria- Gram-negative: has inner and outer membrane (outer is over peptidoglycan layer)- Gram-positive: only has inner membrane under peptidoglycan layerHow vancomycin works- Doesn’t work with enzyme only; it attacks peptidoglycan- Enzyme cannot assemble the scaffold- Can be vancomycin sensitive or resistantCells walls are not the only way of attack5 ways antibiotics can work:- Inhibition of cell wall synthesis (penicillin, cephalosporin, vancomycin, bacitracin- Injury to plasma membrane (polymyxin B, mystatin, amphotericin B, miconazole- Inhibition of synthesis of essential metabolites (trimethoprim)- Inhibition of nucleic acid replication and transcription (rifampin, quinolones) - Inhibition of protein synthesis (streptomycin, erythromycin, tetracycline)- About 70% of bacteria that cause infections in hospitals are resistant to at least one of the drugs most commonly used to treat infections- Nearly 2 million patients get an infection in a hospital each yearo 90,000 die as a resultMicrobes: organisms too small to be seen by unaided eye (bacteria, protists, archae, and fungi)- Why are viruses not included here?Antibiotic resistance: How and why?1. Review evolution by natural selection2. Apply to evolution of antibiotic resistanceVertical gene transfer: binary fissionMain points to mention in letter- Antibiotics- Genes- Mutations- Adaptations- DNA changes- Resistance to antibiotics- Natural selection- Gene transfer (horizontal)Taken to hospital with serious bacterial infection; TO ensure you are treated w/ most effective antibiotic your doctor culture your bacteriaA pure culture can be tested for antibiotic resistance by evenly swabbing it over an agar plate and pressing discs of diff antibiotics. After a period of incubation (bacterial growth), sensitivity or resistance to antibiotics can be determined by measuring the zone that forms around the discs.Antibiotic disc with less clear space around it is the most resistant because none of the bacteria is being inhibited; antibiotic disc with the most clear space around it is the least resistant because Clicker: You feel better after taking your antibiotic pills for 6 days. The infection seems to be gone and since the antibiotics give you an upset stomach. What should you do?A stop right away C take them for 10 daysB take them for another day D take them until they are gone- Bacteria could not be completely gone- Last bacteria left would be the most resistant- Not finishing regimen can contribute to resistance- Taking it for viruses can also lead to resistance as wellWhy does it happen so fast?- Our part: selection for resistant variantsTriclosan (antibiotic)- Implicated in causing damage in hormonal system- Breeding resistant bacteria in your