Bacterial Genetics

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
10
Specialized Transduction
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
A
2 min
H
3 min
1 min
C
27
Interrupted Mating Mapping