Genetics of Bacteria

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???????????????????????(Genetics of Bacteria)

• ???????????? ???????????????????????????????????
• 1. ???????????????????????????????????????????????
  TRANSFORMATION, CONJUGATION, ???
• TRANSDUCTION
• 2. ?????????????????????????????????????????????

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????????????????????

• Introduction to Genetics. 2000.
• Griffith et al.
• 2. Genetics. 1992. Weaver Hedrick.
• 3. Molecular Genetics of Bacteria. 1989. Dale J.
• 4. ???????????. 2542. ???????? ?????????.
• 5. ???????????. 2528. ???????? ?????.
• 6. websitegtconservation genetics
• 7. ?????? ????????

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Prokaryotes blue-green algae (cyanobacteria)
bacteria Simple Chromosome (no nuclear
membrane) ???? monoploid Bacteriophage virus
that parasitize bacteria (phage)
no meiosis
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Transformation A bacterial cell acquired a
piece of DNA from the environment and incorporate
this DNA into its own chromosome
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Conjugation One bacterial cell
transfers DNA segments to another cell by direct
cell-to-cell contact
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Transduction
Bacterial viruses pick up a piece of DNA from one
bacterial cell and inject it into another, in
corporate into the chromosome
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????????????????????????

• BACTERIA
• (Not all)
• Exchange genetic information
• Artificial Nature
• Transformation Conjugation Transduction

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TRANSFORMATION

• Griffith ????? Transformation ????????????????????
  ???????????????? (Pneumococcus pneumoniae)
• ?????????????? e.g. Streptococcus, Bacillus
  subtilis, E. coli
• ??????????????? ???????????????

????????
????????
??????????????????
DNA
enzyme
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????????????????????? Transformation

• ??????????????????????????????? DNA
• (15 molecules ?????? ??? 1 ??????????????)
• ????????????????
• -????????????????????? transformation
  ????????????????????????
• -DNA ??? mammalsgt transformation ?? E. coli
  ???

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PLASMID

• ???????? DNA ?????????????????? minichromosome
• ????????? ??????????????????2-3
  ?????????????????????????????????????? plasmid
  ??????????????????????????????????????????????????
  ????????????????????????????? ???????? EPISOME
  ???????????? F factor ??????? E. coli

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Basic procedure for plasmid transformation of E.
coli

• Bacterial cell takes up isolated DNA molecules
  from the medium surrounding it.
• Artificial pretreatment of the cells of many
  bacterial species is only readily demonstrated
  and probably does not occurs naturally.
• Transformation occurs in nature is also limited
  by the presence of nucleases (Endonuclease
  Ligase) in many environments.

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?????????????? transformation

• ???????? DNA ???????????????????????????
  ?????????????????????????????
• ????????? active transport ???????????????????????
  ????????????
• ???????? DNA ????????? polynucleotide
  ???????????????????? ???????? DNA
  ??????????????????????????????????????????????????
  ??
• gt????????????????????????????? ????
  recombination
• ???????????????????????????? recombination
  ?????????????? heteroduplex
• gt ?????????????????????????????---gt
  ????????????????????????? 2 ??????????? DNA
  ?????????? recombination ?????????? homoduplex

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E. coli plasmid transforma-ting
????? Molecular genetics of bacteria 1989. P. 56
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CONJUGATION

• Direct contact between bacterial cell
  CONJUGATION
• 
  
• SEX pili (????)
• DNA ???????
• ?

F Fertility factor
F- NO fertility factor
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????? Introduction to Genetics. 2000. Griffith
et al.
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minimal medium a substrate containing
only inorganic salts, a carbon source for
energy, and water for bacterial growth without
nutrient supplements
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Wild type bacteria Prototrophic
Can grow colonies on minimal medium
Can not grow unless specific nutrients (adenine,
biotin et.) are added
Mutant clones Auxotrophic
? Geneticist can distinguish different phenotypes
among plated colonies
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Genotypic symbols phenotype bio- ????????????????
??? biotin ???????? minimal medium
arg- ??????????????????? arginine ????..
met- ??????????????????? methionine ????..
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Genotypic symbols phenotype lac- ????????????????
???????? lactose ???????????????? gal- ???????????
????????????? galactose ???????????????? strr ???
???????????????????????????????????????? strs ????
??????????????????????????????????
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Discovery of conjugation
???????????????????????????????????????? ?.?.
1946 Joshua Lederberg Edward
Tatum ??????????????? E. coli ?????????????? str
ain A ??? strain B
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????? An Introduction to Genetic Analysis. 2000.
Griffith et al.
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CONJUGATION EXPERIMENT
(a)
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Strain B ????? fertility factor F-
BACTERIA
Strain A ?? fertility factor F
A B
???? Direct contact ???????? DNA ?????????? F
pilus (????)
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????? An Introduction to Genetic Analysis. 2000.
Griffith et al.
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CONJUGATINGE. coli
????? Introduction to Genetics. 2000. Griffith
et al.
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How do we know the F factor consists of genes?
Experiment
new species of DNA appeared in the S. marcescous
and its density matched that of E. coli
E. coli ??? F S. marcescens ??? DNA
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Hfr bacteria mutant F strains but lost
the ability to transfer fertility at high
frequency
Instead, they transfer host chromosomal genes at
high frequency
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CONJUGATION
????? Molecular genetics of bacteria. 1989. P.
59.
Transfer of DNA by conjugation
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Mechanism of plasmid DNA transfer by CONJUGATING
????? Molecular genetics of bacteria. 1989. P.
60.
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????????????????????? CONJUGATION

• Conjugation tube
• F factor (Sex factor F plasmid)
• ???????????????????? F factor ???????? F
• ??????????????????????? F factor ???????? F-
• ??????? F factor (1) ????????????? (2)
  ?????????????? chromosome
• ????????? Hfr
• ???????? ?????????????????????
  ????????????????????????????

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TRANSDUCTION
The use of phages to carry bacterial genes into
new host cells
SPECIALIZED
GENERALIZED
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TRANSDUCTION

• ????????????????????/?????????????????????????????
  ??????????????????????????????????????????????????
  ????????????????????????? Bacteriophage
• Bacteriophage (phage) ?? 2 ????
• virulent and temperate (prophage) ????????????
• ?????? ??? E. coli

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Generalized transduction (??????????????????)
??????????
???????????????
???????????????
??????
???????????
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PROPHAGE

• DNA ???????????????? temperate phage
  ???????????????? chromosome ??? bacteria
  ???????????????????? chromosome ??? bacteria
  ????????????????????????????? bacteria
• prophage ?????????????????????????????????????????
  ???? ??? Lambda (???????) ??? E. coli

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Generalized TRANSDUCTION
????? Molecular genetics of bacteria. 1989. P.
68.
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(No Transcript)
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???????? Lambda transducing phages
?????????????????? transduction

• Normal excision
• (b) Right excision
• (c) Left excision

????? Genetics of Bacteria and phages. In
Genetics. 1992. Weaver RF Hedrick PW. PP. 387
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Generalized transduction (??????????????????)
??????????
???????????????
???????????????
??????
???????????
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????? An Introduction to Genetic Analysis. 2000.
???? 232, Griffith et al.
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SEXDUCTION

• ????????????? F factor ?????????
  ???????/??????????????????????????????????????????
  ??????????????

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Localized transduction (?????????????????????)
??????????????? ????????????? ????????????? ??????
??????? ???????????
???????
???????????????
????????? ????????????? ???????