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Bacterial Genetics

Bacterial Genetics. Transformation incorporation of exogenous DNA Transduction virally mediated gene transfer Conjugation pseudo-sexual reproduction. One-way transfers!. Transformation. Incorporation of exogenous DNA Bacteria must be “competent” produce specialized proteins

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Bacterial Genetics

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  1. Bacterial Genetics • Transformation • incorporation of exogenous DNA • Transduction • virally mediated gene transfer • Conjugation • pseudo-sexual reproduction One-way transfers!

  2. Transformation • Incorporation of exogenous DNA • Bacteria must be “competent” • produce specialized proteins • competence may be triggered • DNA segments must be small • ~ 500 kb

  3. Transformation

  4. Transformation

  5. Transformation

  6. Transduction • Temperate virus attacks bacterium • Picks up part of bacterial chromosome when lytic • Transfers bacterial chromosome to new host

  7. Specialized Transduction

  8. Specialized Transduction

  9. Specialized Transduction a a

  10. Specialized Transduction a a A

  11. Specialized Transduction a

  12. Conjugation • Requires donor strain and recipient strain • one-way transfer of material from donor to recipient • donor strain has F factor - a plasmid • plasmid = DNA independent of chromosome

  13. Conjugation • During NORMAL conjugation, F factor ONLY is transferred • Some specialized types of conjugation may transfer chromosomal material also • HFR strains • High Frequency of Recombination

  14. Conjugation Sex pillus F+ F-

  15. Conjugation F+ F-

  16. Conjugation F+ F-

  17. Conjugation F+ F-

  18. Conjugation F+ F+

  19. HFR Conjugation • Parts of chromosome are donated • F factor inserts into chromosome • now called HFR mating type • HFR X F--

  20. HFR Conjugation HFR F+

  21. HFR Conjugation A a HFR F--

  22. HFR Conjugation A A a HFR F--

  23. HFR Conjugation a A x x A A a F-- HFR

  24. Interrupted mating technique • Map bacterial loci based on timing of transfer during Hfr conjugation • Start conjugation, sample at timed intervals • Tells order, distance between loci • Need several different Hfr strains for complete map

  25. Interrupted Mating Mapping 1 min 2 min 3 4 5 6

  26. 2 min E B 1 min 2 min A H 3 min 1 min C

  27. Interrupted Mating Mapping

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