Lambda phage is a bacteriophage that infects E. coli bacteria. It has two life cycles: a lytic cycle and a lysogenic cycle. In the lytic cycle, the phage genome is transferred into the bacterial cell where it replicates and causes the bacterial cell to burst, releasing new phage particles. In the lysogenic cycle, the phage genome integrates into the bacterial chromosome and replicates with the host DNA without killing the cell. The phage can switch between these two cycles depending on environmental conditions inside the infected bacterial cell.

1. Life cycle of λ phage
Presented by:
Minhaz Ahmed
BBI11014
Integrated M.Sc 3rd
semester,MBBT,
Tezpur University, Assam

2. CONTENTS
 Introduction
 How genome is transferred
 Lytic cycle and lysogenic cycle
 Life cycle
 Lytic or lysogenic?

3. What is lambda phage?
 It is a bacterial virus, or
bacteriophage , that infects the
bacterial species Escherichia coli.
 This virus is a temperate phage.
 Temperate phages are basically
bacteriophages which can choose
between a lytic and lysogenic
pathway of development.
SOURCE:classes.midlandstech.edu

4. The viral DNA exists as
a separate molecule
within the bacterial cell.
 Replicates separately
from the host bacterial
DNA.

Viral DNA integrates
with bacterial DNA.
Replicates with the
host DNA

5. How it penetrates:
It binds to the target E. coli cell, via J protein in the tail
tip that interacts with the maltoporin of E. coli and
injects its linear genome.
TAIL FIBRE
TAIL
HEAD
1
DNA
COLLAR
BASE PLATE
DNA of E. coli
MALTOPORIN in E. coli
2
E. coli

6. LIFE CYCLE :
SOURCE: Pearson Education 2004

7. Lytic or lysogenic?
1.lytic life cycle:
occurs in cells with sufficient nutrients, protease
activity is high, which breaks down cII.
2.Lysogenic life cycle:
In cells with limited nutrients, protease activity is
low, making cII stable.
 Computer modeling and simulation suggest that random processes
during infection drive the selection of lysis or lysogeny within individual
cells.
However, recent experiments suggest that physical differences
among cells, that exist prior to infection, predetermine whether a cell
will lyse or become a lysogen.

8. THANK YOU