Microbial genetics for exam 3

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Microbial genetics for exam 3

  1. 1. MICROBIAL GENETICS & MICROBIAL INTERACTIONS Last Lecture Sets for Examination 3Monday, February 27, 2012
  2. 2. MICROBIAL GENETICSMonday, February 27, 2012
  3. 3. TERMS IN MICROBIAL GENETICS Genome: All of the genetic material in a cell Genomics: The molecular study of genomes Genotype: The genes of an organism Phenotype: Expression of the genesMonday, February 27, 2012
  4. 4. OVERVIEWMonday, February 27, 2012
  5. 5. IMPORTANT ENZYMESMonday, February 27, 2012
  6. 6. REGULATION OF GENE EXPRESSIONMonday, February 27, 2012
  7. 7. MUTATIONS A change in the genetic material Mutations may be neutral, beneficial, or harmful Mutagen: Agent that causes mutations Spontaneous mutations: Occur in the absence of a mutagenMonday, February 27, 2012
  8. 8. TYPES OF MUTATIONS: MISSENSEMonday, February 27, 2012
  9. 9. TYPES OF MUTATIONS: NONSENSEMonday, February 27, 2012
  10. 10. TYPES OF MUTATIONS: FRAMESHIFTMonday, February 27, 2012
  11. 11. REPAIRING MUTATIONS Ionizing radiation (X rays and gamma rays) causes the formation of ions that can react with nucleotides and the deoxyribose-phosphate backbone Nucleotide excision repairs mutations. UV radiation causes thymine dimers Light-repair separates thymine dimers.Monday, February 27, 2012
  12. 12. MUTATIONS IN THE LAB FREQUENCY: Spontaneous mutation rate = 1 in 109 replicated base pairs or 1 in 106 replicated genes AND Mutagens increase to 10–5 or 10–3 per replicated gene SELECTION: Positive (direct) selection detects mutant cells because they grow or appear different Negative (indirect) selection detects mutant cells because they do not grow.Monday, February 27, 2012
  13. 13. CHARACTERIZING MUTATIONSMonday, February 27, 2012
  14. 14. CHARACTERIZING MUTANTS HYPOTHETICAL EXPERIMENT: Using UV as mutagen you isolated colonies on your NA plates, to verify possible effects on phenotypes, you TEST MEDIA ISOLATE 1 ISOLATE 2 ISOLATE 3 MINIMAL MEDIUM (MM) - - - MM + Penicillin + - - MM + Erythromycin - - + MM + Rifampicin - + + MM + glycine + - - MM + serine - - - MM + methionine - + -Monday, February 27, 2012
  15. 15. CHARACTERIZING MUTANTS TEST MEDIA ISOLATE 1 ISOLATE 2 ISOLATE 3 MINIMAL MEDIUM (MM) - - - MMG + Penicillin + - - MMG + Erythromycin - - + MMG + Rifampicin - + + MM + glycine + - - MM + serine - - - MM + methionine - + -Monday, February 27, 2012
  16. 16. CHARACTERIZING MUTANTS TEST MEDIA ISOLATE 1 ISOLATE 2 ISOLATE 3 MINIMAL MEDIUM (MM) - - - MMG + Penicillin + - - MMG + Erythromycin - - + MMG + Rifampicin - + + MM + glycine + - - MM + serine - - - MM + methionine - + - Do you believe that they are all mutants? Justify.Monday, February 27, 2012
  17. 17. CHARACTERIZING MUTANTS TEST MEDIA ISOLATE 1 ISOLATE 2 ISOLATE 3 MINIMAL MEDIUM (MM) - - - MMG + Penicillin + - - MMG + Erythromycin - - + MMG + Rifampicin - + + MM + glycine + - - MM + serine - - - MM + methionine - + - Do you believe that they are all mutants? Justify. Which isolate(s) has mutations that resulted to antibiotic resistance? Justify.Monday, February 27, 2012
  18. 18. CHARACTERIZING MUTANTS TEST MEDIA ISOLATE 1 ISOLATE 2 ISOLATE 3 MINIMAL MEDIUM (MM) - - - MMG + Penicillin + - - MMG + Erythromycin - - + MMG + Rifampicin - + + MM + glycine + - - MM + serine - - - MM + methionine - + - Do you believe that they are all mutants? Justify. Which isolate(s) has mutations that resulted to antibiotic resistance? Justify. Which isolate(s) has mutations on the inability to produce an amino acid? Justify.Monday, February 27, 2012
  19. 19. CHARACTERIZING MUTANTS TEST MEDIA ISOLATE 1 ISOLATE 2 ISOLATE 3 MINIMAL MEDIUM (MM) - - - MMG + Penicillin + - - MMG + Erythromycin - - + MMG + Rifampicin - + + MM + glycine + - - MM + serine - - - MM + methionine - + - Do you believe that they are all mutants? Justify. Which isolate(s) has mutations that resulted to antibiotic resistance? Justify. Which isolate(s) has mutations on the inability to produce an amino acid? Justify. How will you name your isolate (E. coli) as a new strain?Monday, February 27, 2012
  20. 20. MUTAGENICITY TEST: AMES TESTMonday, February 27, 2012
  21. 21. Monday, February 27, 2012
  22. 22. SINCE IT’S V-DAY....Monday, February 27, 2012
  23. 23. SINCE IT’S V-DAY.... LET’S TALK ABOUT SEX!!!Monday, February 27, 2012
  24. 24. SINCE IT’S V-DAY.... LET’S TALK ABOUT SEX!!! Interested?Monday, February 27, 2012
  25. 25. SINCE IT’S V-DAY.... LET’S TALK ABOUT SEX!!! Interested?Monday, February 27, 2012
  26. 26. SINCE IT’S V-DAY.... LET’S TALK ABOUT SEX!!! Interested? MICROBIAL GENETICSMonday, February 27, 2012
  27. 27. GENE TRANSFERS ENDPOINT: RECOMBINATION Vertical gene transfer: Occurs during reproduction between generations of cells Horizontal gene transfer: The transfer of genes between cells of the same generation CONJUGATION, TRANSFORMATION, TRANSDUCTIONMonday, February 27, 2012
  28. 28. CONJUGATIONMonday, February 27, 2012
  29. 29. CONJUGATIONMonday, February 27, 2012
  30. 30. TRANSFORMATIONMonday, February 27, 2012
  31. 31. TRANSDUCTIONMonday, February 27, 2012
  32. 32. EXTRACHROMOSOMAL INHERITANCE: PLASMIDS Conjugative plasmid: Carries genes for sex pili and transfer of the plasmid Dissimilation plasmids: Encode enzymes for catabolism of unusual compounds R factors: Encode antibiotic resistanceMonday, February 27, 2012
  33. 33. SOME METABOLIC ACTIVITIES DETERMINED BY PLASMIDS ORGANISM ACTIVITY Pseudomonas spp degradation of camphor, toluene, octane, salicyclic acid Bacillus stearothermophilus alpha amylase Alcaligenes eutrophus utilization of hydrogen as oxidizable energy source E. coli sucrose uptake and and metabolism, citrate uptake Klebsiella spp nitrogen fixation lactose utilization, galactose phosphotransferase system, citrate Streptococcus (group N) metabolism Rhodospirillum rubrum synthesis of photosynthetic pigment Flavobacterium spp nylon degradationMonday, February 27, 2012
  34. 34. EXTRACHROMOSOMAL INHERITANCE: TRANSPOSONS Segments of DNA that can move from one region of DNA to another Contain insertion sequences for cutting and resealing DNA (transposase) Complex transposons carry other genesMonday, February 27, 2012
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