Bacteriophage Life Cycle – Imaluop

Now we are going to discuss the bacteriophage Life cycle which will give you a general overview of how a bacteriophage is able to destroy a large number of bacteria cells and how it is sometimes beneficial for us against harmful bacteria. 

What is Bacteriophage: 

Some viruses infect bacteria and multiply very high rate inside the bacterial cell using resources in a bacterial cell and finally they destroy the bacteria cells and infect a new bacterial cell which continues multiple times.

Bacteriophages are either RNA viruses or DNA viruses and their genome may contain four to few thousand genes which code for their structural proteins.

Viral genomes enter into the bacterial and make their multiple copies and they also produce capsid for their complete form, finally when they synthesize all parts required for a whole viral body then they destroy the bacterial cell and come outside of the bacterial cell. 

Structure of A Bacteriophage: 

Bacteriophages have a polyhedral head which is formed by 2000 capsomeres and it encloses the main genome of the bacteriophage inside and there is a short collar next to the head region.

Their tail region is highly modified for infecting bacteria cells and the tail has a tubular structure which is enclosed by a contractile sheath.

The contractile sheath is formed by circular ring made by protein and at the end of the tail there are a plate like structure which is known as basal plate and at the corner of basal plate there are some spike like structure present which are known as tail fibres which helps the Bacteriophage to attach with bacterial cell.  

Bacteriophage Life Cycle: 

In bacteriophage two types of behaviour observed in their life cycle one is lytic cycle or virulent cycle while another one is lysogenic cycle or temperate cycle which and we will discuss each type of life cycle below one by one. 

Lytic Cycle or Virulent Cycle: 

In this case bacteriophage attack a bacterial cell and make its copy inside the bacterial cell when they produce sufficient copy of the virus then they go outside of the bacterial cell but the bacterial cell bursts and is destroyed by this activity of bacteriophage, it occurs in some stages which we will discuss now. 

Adsorption: 

In the first stage the Bacteriophage comes close to the bacterial cell and attached to the bacterial cell wall with the help of their tail fibres which attach to the receptors present on the surface of the bacterial cell and this phenomenon is known as adsorption. 

Penetration: 

When the basal plate and tail fibres attached to the bacterial cell wall then the contractile sheath on the tail contract and the bacteriophage secrete a chemical on bacterial cell wall which weaken the bacterial cell wall and the tube like core present in tail enter into the bacterial cell wall which cause the entry of bacteriophage DNA into the bacterial cell.  

Synthesis of Bacteriophage Components: 

Inside the infected bacteria cell the phase genome multiply and make its copy along with different structural proteins inside the the bacterial cell like capsid subunit of different parts like head, contractile sheath. 

Maturation and Assembly: 

After the formation of each part of bacteriophage they form the complete structure of the Bacteriophage, head protein enclose the phase DNA, tail protein assembled to form complete bacteriophage. 

Release of Bacteriophage: 

The progeny Bacteriophage bursts the cell wall of the bacteriophage and comes outside of the bacterial cell which causes destruction of bacterial cells in large numbers and numerous bacteriophages are formed within a short time span. 

Lysogenic Cycle: 

In this case after the Bacteriophage genome enters inside a bacterial cell but does not start a lytic cycle instantly but the phase genome integrates with bacterial cells and multiply their number when bacterial genomes replicate.

So the phase genome multiply generation after generation during reproduction of bacteria and the bacterial genomes with phase genome is known as prophase. 

Read More: Barr Body and Lyon’s Hypothesis