Life cycle of  λ phage

Presented by:Minhaz AhmedBBI11014Integrated M.Sc 3rd semester,MBBT,Tezpur University, Assam

CONTENTS Introduction

How genome is transferred

Lytic cycle and lysogenic cycle

Life cycle

Lytic or lysogenic?

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

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

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.

DNAHEADTAIL

COLLARMALTOPORIN in E. coliBASE PLATE

DNA of E. coli

E. coli

TAIL FIBRE1

2

LIFE CYCLE :

SOURCE: Pearson Education 2004

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.

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