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