Bacterial Conjugation and Transduction – Imaluop

Bacterial Conjugation and Transduction: Bacteria multiply in our nature very quickly due to its high rate of growth and capability to divide by the method of binary fission and it is a method for genetic material transfer from one parent bacteria to new bacteria but it is known as vertical transmission.  

But bacteria show other different methods for transferring the mutation from one bacteria to another bacteria which is known as horizontal transmission and there are three types of horizontal transmission method in bacteria – conjugation, transduction and transformation. 

Bacterial Conjugation Basic Idea: 

Lederberg and Tatum discovered this method of horizontal transmission in Escherichia Coli where plasmid of a bacteria is transferred to another bacteria when they come close and in this process F factors are transferred. 

Bacterial Conjunction Mechanism: 

Transfer of plasmid by bacterial conjugation occurs in some step in first step pilus formation. Pilus of the donor cell or F+ cell creates contact with the pilus of the recipient cell or F- cell which is known as pilus formation.

Then on the next step both the pilus of donor and recipient bacterial cells fuse together to make a direct physical contact between them which makes the transfer of F plasmid easy. 

Bacterial Transduction Basic Idea: 

It is a method of horizontal transmission in bacteria which occurs with the help of bacteriophage; they are not able to transfer plasmid independently like conjugation and it occurs at a very high rate.

Bacteriophage are some small sized viruses who infect the bacteria and complete their life cycle inside the cell of bacteria and they multiply very quickly inside the bacterial cell using various resources from the bacterial cell.

This type of horizontal transmission can occur in two ways: one is generalized transduction while other is specialised transduction. 

Generalized Transduction: 

In this type of transduction bacteriophage infect the bacteria and viral genome enter into the bacterial cell where the viral genome multiply their copy using the cellular machinery of the bacterial cell.

When the viral genome makes its numerous copy and synthesis of their structural proteins to develop their complete body then bacterial genomes split into several fragments by the enzymes of bacteriophage and finally the bacterial cells bursts due to the action of lysine releases by the bacteriophage.  

Specialised Transduction:  

Here only some selected bacterial genomes are transmitted from one bacteria to another bacteria due to the lysogenic activity of bacteriophage. In some cases the viral genome does not start to replicate its copy after entering the bacterial cell instantly.

The viral genome gets incorporated into the bacterial genome and remains in dormant stage for some time but meanwhile the viral genome goes inside several bacterial cells generation after generation.

When the viral genome present in the bacterial genomes induce to make their copy they become active and start a lysogenic cycle but sometimes the phage genome carries bacterial genomes with it.

When the bacteriophage infect a new bacterial cell the bacterial genomes present on the phage genome incorporate into the new bacterial genomes which cause selected transmission of bacterial genomes.  

Bacterial Transformation Basic Idea: 

This special method of horizontal transmission was first observed by Griffith in Streptococcus Pneumoniae bacteria where bacterial cells can uptake DNA from their surroundings and the bacterial cells who can uptake external DNA are called competent cells.

All bacterial cells can not uptake DNA from their external environment but we can promote uptake of DNA by using different methods artificially. Bacterial cells are placed in a very cold environment which is created artificially and it changes the permeability of the bacteria in the presence of calcium phosphate.

Then they are incubated with external DNA and heat shock is applied which causes forceful entry of DNA inside bacteria. Electric pulses also can be applied to perform electrophoresis which cause entry of external DNA into the bacterial cells artificially. 

Read More: Bacteriophage Life Cycle