Download Bacterial and Phage Recombination

Colossians 1:16, 17
16 For by him were all things created,
that are in heaven, and that are in
earth, visible and invisible, whether
they be thrones, or dominions, or
principalities, or powers: all things
were created by him, and for him:
17 And he is before all things, and by
him all things consist.
©2000 Timothy G. Standish
Bacterial Genetics
Timothy G. Standish, Ph. D.
©2000 Timothy G. Standish
Bacteria Have Circular
Chromosomes
Cell Wall
Cell Membrane
Chromosome
Origin of
Replication
Cytoplasm
Termination of
Replication
©2000 Timothy G. Standish
Replication
Replication goes
in both directions
Original
Chromosome
Start of replication
Theta (q) structure
Mid replication
End of replication
Two chromosomes
©2000 Timothy G. Standish
Binary Fission
©2000 Timothy G. Standish
Genetic Recombination
If bacteria were incapable of genetic
recombination, all members of a given species
would be clones with differences arising only due
to mutations in different lines
If bacteria could not share genetic information as
other organisms do in sexual reproduction, there
would be vastly less opportunity to adapt to
different environments
As it turns out, bacteria are notorious for their
ability to adapt, thus it is not surprising that
elegant mechanisms exist for sharing genetic
information
©2000 Timothy G. Standish
Ways Bacteria Exchange
Genetic Material
1 Transformation - Bacteria take up DNA
from their environment and incorporate it
into their genome (i.e. the Griffith
experiment)
2 Conjugation - The direct transfer of DNA
by bacteria usually via plasmids
3 Transduction - Movement of DNA
between bacteria by viruses
©2000 Timothy G. Standish
1 Transformation
Crossing
over
Insertion
©2000 Timothy G. Standish
1 Transformation
©2000 Timothy G. Standish
1 Transformation
©2000 Timothy G. Standish
1 Transformation
©2000 Timothy G. Standish
1 Transformation
©2000 Timothy G. Standish
1 Transformation
©2000 Timothy G. Standish
Crossover Frequency
Following binary fission, one daughter cell will
have the recombinant strand and thus have a
recombinant chromosome
Mapping bacterial genes following
transformation is not significantly different from
eykaryotic mapping. The closer two genes are to
one another, the lower the probability of a
crossover event between them and thus the higher
the probability that they will be co-transformed
A
A
B
B
C
C
Transformation
with A and C is
unlikely
©2000 Timothy G. Standish
F plasmid
2 Conjugation
F+ bacteria
Mating Bridge
F- bacteria
F
plasmid
©2000 Timothy G. Standish
F plasmid
2 Conjugation
F+ bacteria
Mating Bridge
F- bacteria
F
plasmid
©2000 Timothy G. Standish
F plasmid
2 Conjugation
F+ bacteria
Mating Bridge
F- bacteria
F
plasmid
©2000 Timothy G. Standish
F plasmid
2 Conjugation
F+ bacteria
Mating Bridge
F- bacteria
F
plasmid
©2000 Timothy G. Standish
F plasmid
2 Conjugation
F+ bacteria
Mating Bridge
F- bacteria
F
plasmid
F
plasmid
©2000 Timothy G. Standish
Hfr Recombination
F+ bacteria
F plasmid
Integration
Hfr cell
F- bacteria
Transfer of
genetic material
©2000 Timothy G. Standish
Hfr Recombination
F+ bacteria
F plasmid
Integration
Hfr cell
Interruption
of conjugation
F- bacteria
Crossing over
Transfer of
genetic material
©2000 Timothy G. Standish
Hfr Recombination
F+ bacteria
F plasmid
Integration
Hfr cell
F- bacteria
Recombinant
Bacteria
©2000 Timothy G. Standish
3 Transduction
Generalized
Infection
Destruction of
the bacteria’s
DNA
Production of
viral parts
Lysis
Packaging
Replication of
the viral
genome
©2000 Timothy G. Standish
Temperate
Phage
3 Transduction
Specialized
Part of the
bacteria’s
DNA
Production of
viral parts
Lysis
Packaging
Replication of
the viral
genome
©2000 Timothy G. Standish
©2000 Timothy G. Standish