Last updated on June 14th, 2021
In a bacterial population, DNA can be transferred from one organism to another by the horizontal transfer mechanism (apart from vertical inheritance). The DNA thus transferred by lateral/horizontal method can be stably incorporated in the recipient, and changes the genetic composition of the recipient permanently.
Three broad mechanisms mediate the efficient movement of DNA between cells- conjugation, transduction, and transformation.
- Conjugation: Transfer of genes between cells that are in physical contact with one another
- Transduction: Transfer of genes from one cell to another by a bacteriophage
- Transformation: Transfer of cell-free or “naked” DNA from one cell to another
- Conjugation was the first extensively studied method of gene transfer
- Conjugation requires donor cell-to-recipient cell contact and is mediated by sex pilus
- The process occurs between two living cells
- Requires mobilization of donor bacterium’s chromosome/ plasmid
- Plasmid are genetic elements most frequently transferred by conjugation
- Phage mediated genetic recombination in bacteria i.e. phage is used to transfer DNA from one bacterium to another
- Transducing particle: bacterial nucleic acid in phage coat
- There are two broad categories of transduction
- For artificial genetic recombination purpose, the temperate phage is the preferred vehicle for gene transfer
- Transduction has been found to occur in a variety of bacterial populations including:
- Escherichia coli
- Pseudomonas spp
- Salmonella spp
- Staphylococcus spp
- Recipient cells uptake free DNA released into the environment.
- DNA is released into the environment when another bacterial cell (i.e. donor) dies and undergoes lysis
- Not all bacteria are able to go for transformation, only some bacteria are able to take free DNA and are able to go transformation. These types of bacteria are called competent bacteria.
- Pathogenic bacteria showing competence
- Haemophilus spp
- Streptococcus spp
- Neisseria spp