1 / 34

LECTURE 9: GENETICS OF BACTERIA & THEIR VIRUSES II

LECTURE 9: GENETICS OF BACTERIA & THEIR VIRUSES II. bacterial conjugation (rev) bacterial transformation bacteriophage genetics. BACTERIAL CONJUGATION. interrupted-mating selective markers donor is str s recipient is str r origin of replication transferred first

reed
Download Presentation

LECTURE 9: GENETICS OF BACTERIA & THEIR VIRUSES II

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. LECTURE 9: GENETICS OF BACTERIA & THEIR VIRUSES II • bacterial conjugation (rev) • bacterial transformation • bacteriophage genetics

  2. BACTERIAL CONJUGATION • interrupted-mating • selective markers • donor is strs • recipient is strr • origin of replication transferred first • 1st transferred markers most frequent in exconjugants

  3. BACTERIAL CONJUGATION • bias in recovery of markers • gradient of transfer used fordetermination of gene orderonly

  4. Schaum’s Outlines – Genetics 3rd Ed., CH12, pp. 321 – 325 4th Ed., CH10, pp. 349 – 355

  5. BACTERIAL CONJUGATION • exogenote enters cell ... merozygote = partial diploid • single recombination event (3x, 5x, ...) nonviable • double recombination event (4x, 6x, ...) viable

  6. BACTERIAL CONJUGATION • bias in recovery of markers • gradient of transfer used fordetermination of gene orderonly •  to determine map distances, select late marker to ensure transfer of all relevant genes ... high resolution mapping

  7. BACTERIAL CONJUGATION • high-resolution mapping by recombinant frequency

  8. Schaum’s Outlines – Genetics 3rd Ed., CH12, pp. 321 – 325 4th Ed., CH10, pp. 349 – 355

  9. TRANSFORMATION IN BACTERIA • conversion of one genotype to another by uptake of exogenous DNA • transformation principle – demonstrated that DNA was responsible for inherited differences in polysaccharide character of S. pneumoniae (CH8)

  10. TRANSFORMATION IN BACTERIA • extracted DNA (in an experiment) breaks at random • co-transformation of 2 tightly linked donor genes is more likely than 2 distant donor genes • cells must be made competent to enable DNA entry • detergents • electrical fields

  11. TRANSFORMATION IN BACTERIA • dependent on concentration of DNA in the medium

  12. TRANSFORMATION IN BACTERIA • DNA must enter and recombine into the host

  13. TRANSFORMATION IN BACTERIA • practice question, p. 237, #18

  14. BACTERIOPHAGE GENETICS • bacteriophage = eaters of bacteria • T-phages well studied; T-even and T-odd

  15. BACTERIOPHAGE GENETICS • bacteriophage = eaters of bacteria • T-phages well studied; T-even and T-odd

  16. BACTERIOPHAGE GENETICS

  17. BACTERIOPHAGE GENETICS • lysis = breaking of cell wall and release of phage particles • bacteriophage lytic cycle ...

  18. BACTERIOPHAGE GENETICS • phage plaques on a lawn of bacteria • 1 plaque forming unit PFU = 1 phage particle • plaque morphology • host range

  19. BACTERIOPHAGE GENETICS • phage cross: h– r+x h+ r– • h+infect strain 1 • h–infect strains 1 & 2 • r+ slow lysis, small plaques • r– slow lysis, large plaques

  20. BACTERIOPHAGE GENETICS • lawn of 2 E. coli strains – 1 immune to h+phage

  21. BACTERIOPHAGE GENETICS • phage cross: h– r+x h+ r– • h+clowdy • h–clear • r+ small • r– large • RF = [h+ r++ h– r–] TOTAL

  22. TRANSDUCTION IN BACTERIA • alternative life cycles of temperate bacteriophage

  23. TRANSDUCTION IN BACTERIA • generalized transduction… random incorporation • lytic cycle, non-integrated phage

  24. thr leu azi TRANSDUCTION IN BACTERIA • co-transduction • donor leu+ thr+ azir recipient leu– thr– azis

  25. TRANSDUCTION IN BACTERIA • genetic map of the purB  cysB region in E. coli

  26. TRANSDUCTION IN BACTERIA • phage integration

  27. TRANSDUCTION IN BACTERIA • specialized transduction… non- random incorporation • lysogenic cycle, integrated phage

  28. TRANSDUCTION IN BACTERIA • specialized transduction… non- random incorporation • lysogenic cycle, integrated phage

  29. TRANSDUCTION IN BACTERIA • transduction: phage acquire host genes and transfer them to other bacterial cells • generalized transduction: transfers any host gene; and occurs when phage randomly packagehost DNA • specialized transduction: faulty separation of prophage (phage incorporated into host genome); new phage contains adjacent host genes only

  30. GENETIC MAPS IN BACTERIA • E. coli linkage map (minutes)

  31. GENETIC MAPS IN BACTERIA • 5 minutes of the E. coli linkage map

  32. GENETIC MAPS IN BACTERIA • correlated genetic and physical maps in E. coli

  33. SUMMARY: RECOMBINATION IN BACTERIA

  34. BACTERIAL CONJUGATION AND RECOMBINATION MAPPING:PROBLEMS • in Griffiths chapter 5, beginning on page 179, add these questions to those listed at the end of lecture #8… #4, 14, 16-21, 24, 28 (eg. in class)-32 • begin with the solved problems on page 177 if you are having difficulty • look Schaum’s Outline (pp. 358-9) • try Schaum’s Outline questions 10.7 – 10.12

More Related