The main difference between conjugation, transformation, and transduction is that conjugation is the transfer of DNA from one living bacterium to another through sex pilus, transformation is the uptake of free DNA released into the environment, whereas transduction is the transfer of DNA from one bacterium to another by bacteriophage.
Conjugation, transformation, and transduction are three methods of horizontal gene transfer in bacteria.
Key Areas Covered
1. What is Conjugation
– Definition, Facts, Importance
2. What is Transformation
– Definition, Facts, Importance
2. What is Transduction
– Definition, Facts, Importance
3. Similarities Between Conjugation Transformation and Transduction
– Outline of Common Features
4. Difference Between Conjugation Transformation and Transduction
– Comparison of Key Differences
Key Terms
Conjugation, Transduction, Transformation
What is Conjugation
Conjugation is one method of horizontal gene transfer in bacteria. It occurs through the direct contact of two bacterial cells through a pilus. Also, it transfers genes for antibiotic resistance, xenobiotic tolerance, etc. Therefore, it is beneficial to the recipient bacterium. Transduction and transformation are the other methods of horizontal gene transfer in bacteria.
Figure 1: Conjugation
Furthermore, conjugation does not form a generation of new organisms. It also occurs through the exchange of genetic material but not the exchange of gametes. Therefore, conjugation is not considered as a method of sexual reproduction. Moreover, the transferring of genetic materials can be either plasmids or transposons in conjugation.
What is Transformation
Transformation is the natural process of uptaking free, foreign DNA that is extracellular by the competent cells of plant, yeast, and bacterial cells. It induces cells to be competent by creating pores on the cell membrane through which naked DNA enters into the cell. It is important in recombinant DNA technology to introduce foreign DNA into bacterial cells.
Figure 2: Bacterial Horizontal gene Transfer
Also, there are three methods of gene transfer by transformation: chemical transformation, electroporation, and particle bombardment. The general method of transformation is the chemical transformation in which the treatment of host cells with calcium chloride makes the cells more permeable to take up exogenous DNA. This cell stage is called competent cells. Then, pores are created on the cell membrane temporarily by a heat shock. In electroporation, cells are made competent by giving an electric shock. Particle bombardment is the general method of transferring DNA into plant cells in which DNA-coated gold or tungsten is forced into the cells physically by a gene gun.
What is Transduction
Transduction is another method of horizontal gene transfer in which the genetic material is deliberately introduced into another cell with the help of bacteriophages. Additionally, bacteriophages, as viral vectors, are an important tool to introduce foreign DNA to the target organism.
Figure 3: Transduction Types
During this process, both viral and host genes can be exchanged between the two genomes. Also, transduction can be done by two different methods based on the type of genetic material that is going to be transferred. They are generalized transduction and specialized transduction. In generalized transduction, any bacterial genes can be transferred via the viral vectors to another host cell. In contrast, in specialized transduction, only a limited or selected set of genes can be transferred into another host cell.
Similarities Between Conjugation Transformation and Transduction
- Conjugation, transformation, and transduction are three methods of gene transfer in bacteria.
- They are mechanisms for horizontal gene transfer between bacteria.
- By these mechanisms, bacteria take up foreign DNA.
- Bacteria get antibiotic resistance through these mechanisms.
- They play an important role in bacterial evolution.
Difference Between Conjugation Transformation and Transduction
Definition
Conjugation refers to the process by which one bacterium transfers genetic material to another through direct contact. Transformation refers to the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings through the cell membrane. In contrast, transduction refers to the process by which a virus transfers genetic material from one bacterium to another.
Vector
Direct cell-to-cell contact occurs in conjugation, free extracellular DNA transfers in transformation, and transducing phages involve in transduction.
Nature of DNA Transferred
Chromosomal and plasmid DNA can transfer by conjugation; any genes or selected genes can transfer by transformation, while any genes can transfer by transduction.
Constraints
Conjugation is only possible for conjugative and mobilizable plasmids; approximately 1% of the species is transformable, while the donor and the host must be in the host range of transducing phage in transduction.
Rate Factors
Pair-wise compatibility of donor and recipient is the rate factor in conjugation, the competence rate of the recipient is the rate factor in transformation, while the size of the phage population common to the donor and recipient is the rate factor in transduction.
Advantages
Conjugation is DNase resistant; transformation can transfer any gene, while transduction is also DNase resistant.
Limitations
In conjugation, only mobile genetic elements such as transposons and mobilizable plasmids can be transferred; transformation is DNase sensitive, and a relatively low range of bacteria can be made competent, while recipient cells need to be capable of homologous or site-specific recombination in transduction.
Conclusion
In brief, conjugation, transformation, and transduction are three methods of horizontal gene transfer. Conjugation occurs through sex pilus by direct cell-to-cell contact. Also, transformation is the uptake of free extracellular DNA. In comparison, transduction is the gene transfer by bacteriophage. Therefore, the main difference between conjugation, transformation, and transduction is the mechanism of gene transfer.
References:
- Khan Academy. (n.d.-a). Conjugation, transformation & transduction | bacteria (article). Khan Academy. https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/mutations-ap/a/genetic-variation-in-prokaryotes#:~:text=Key%20points%3A,through%20a%20tube%20between%20cells.
Image Courtesy:
- “Conjugation” By Adenosine – Own work (CC-BY SA 3.0) via Commons Wikimedia
- “Bacterial horizontal gene transfer” By 2013MMG320B – Own Work (CC-BY SA 3.0) via Commons Wikimedia
- “Transduction illustration” By Momodou Bah – Own Work (CC-BY SA 4.0) via Commons Wikimedia
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