Bacterial viruses
Bacteriophage T4
• Very complex shape,
requiring 20 gene
products for assembly
•
- Capsid (head),
contains linear dsDNA
genome
•
- Tail, consists of
sheath plus internal
tube
Figure 11.2
Bacteriophage T4
• Phage T4 binds to E. coli by contact between its
tail fibers and the outer membrane.
•
- A conformational change causes sheath to
contract and inject the genome into the cell.
Figure 11.4
Fig. 10-15
Nucleases
DNA polymerase
New sigma factors
Tail, collar, base
plate, and tail
fiber proteins
Phage DNA replication
Infection
Early mRNA
Middle mRNA
Early proteins
0
Phage
head
proteins
Phage DNA
5
Late mRNA
Middle proteins
10
15
T4 lysozyme
production
Self assembly
Late proteins
Minutes
Mature phage particle
Lysis
20
25
• Progeny genomes
are linked in a
concatemer.
•
- Cut with an
offset, so that
individual linear
genomes have
slight overlaps
Figure 11.7
Replicative Cycle of Bacteriophage T4
Figure 11.6
• Progeny genomes
are linked in a
concatemer.
•
- Cut with an
offset, so that
individual linear
genomes have
slight overlaps
Figure 11.7
• Each phage particle
is assembled by
convergence of
three pathways
involving head, tail,
and tail fibers.
Figure 11.8
Replicative Cycle of Bacteriophage T4
Figure 11.6