Ch 8 Presentation Slides 1 Pathogenetics ©2006 Lee Bardwell Bio 97 2 Pathogenetics lecture outline 1 • What are bacteria? • What are viruses? • Antibiotic resistance is a big problem – What is an anti[.]
1 Bio 97 Pathogenetics ©2006 Lee Bardwell Pathogenetics lecture outline - • What are bacteria? • What are viruses? • Antibiotic resistance is a big problem – – – What is an antibiotic? Why don't antibiotics kill us? Why don't antibiotics kill viruses? • How bacteria become resistant to antibiotic (biochemical mechanism)? ©2005 Lee Bardwell Genetics of pathogens - • How bacteria become resistant to antibiotic (genetic mechanism)? – What's a plasmid? – What's a transposable element? – How these things move from cell to cell? • What are other ways for DNA to move from cell-tocell? – Transformation – Viral Transduction ©2005 Lee Bardwell Bacterial life cycle Circular chrm s Bacteria • Prokaryotic • Unicellular • Haploid Question Does the statement “loss-offunction alleles are often recessive” make sense when applied to bacteria? â2005 Lee Bardwell Viruses and Phages ã Non-cellular micro-organism • Consist minimally of DNA or R NA genome and some protein • Infect host cells • Can replicate only within host cells • No intrinsic metabolism- relies on host for energy, precursor molecules • No ribosomes - relies on host for protein synthesis ©2005 Lee Bardwell Antibiotic resistance is a big problem in bacteria • Most bacteria isolated from clininal infection are resistant to multiple antibiotics • Some are resistant to all antibiotics in routine use • Some of what used to be the best antibiotics (very effective, few side effects) are now virtually useless ©2005 Lee Bardwell What is an antibiotic ? • A substance that kills or halts the growth of a micro-organism (typically a bacterium) • Usually made by other micro-organisms (fungi, other bacteria) • Examples • Pencillin • Streptomycin • Chloramphenicol ©2005 Lee Bardwell Why don’t antibiotics kill us ? • Bacteria and humans share many core processes Bacteria polymerases resemble human polymerases Bacterial ribosomes resemble human ribosomes, etc • But there are some things that are completely different bacteria have a peptidoglycan cell wall and we don’t • The best (least toxic to us) antibiotics target these “completely different” structures ©2005 Lee Bardwell How antibiotics kill bacteria ? Inhibition of bacterial cell-wall synthesis by certain* antibiotics QuickTime™ and a GIF decompressor are needed to see this picture *penicillin, vancomycin, others NOTE: movies won’t work on downloads/pdfs 10