The key difference between transformation and transduction is that transformation is a mechanism which alters the genetic material of bacteria by direct uptake of exogenous genetic material from its surroundings through the cell membrane and incorporation of it into the genome while transduction is the injection of foreign DNA by a bacteriophage virus into the host bacterium.
Conjugation is a well-known method of DNA recombination, which can be found in both eukaryotes and prokaryotes. Scientists have discovered that it is possible to transfer DNA from one bacterial cell to another by another two mechanisms: transformation and transduction. Similar to conjugation, these two mechanisms transfer DNA in one direction, and recombination occurs between alleles in homologous DNA regions. Both mechanisms transfer very few amounts of DNA and do not transfer the entire cell chromosome.
CONTENTS
1. Overview and Key Difference
2. What is Transformation
3. What is Transduction
4. Similarities Between Transformation and Transduction
5. Side by Side Comparison – Transformation vs Transduction in Tabular Form
6. Summary
What is Transformation?
Fred Griffith, a medical officer in the British Ministry of Health in London, discovered the process of transformation in 1928. It is the mechanism by which bacteria uptake DNA fragments from the environment and incorporate it into their chromosomes. After a successful transformation, the recipient cell (transformant) gains some characteristics which were not present previously within it. In prokaryotes like bacteria, transformation occurs regularly when the cells exist in great numbers, such as in human intestinal tract or in rich soil.
Figure 01: Transformation
In order to carry out a successful transformation, the bacterium should be competent enough. Thus, the transformation or the ability of a cell to uptake extracellular DNA from the environment depends on the competence of the bacterium. The competence depends on variable properties among bacterial species. Transformation can be done artificially; sometimes it even occurs naturally. If it occurs naturally, it increases the potential of causing disease more often.
What is Transduction?
Unlike transformation, transduction requires a virus as an agent to carry DNA fragment from donor to recipient cell. These viruses are bacteria-infecting viruses or bacteriophages. Like all viruses, these bacteriophages have a core of DNA or RNA surrounded by a coat of protein. Bacteriophages attach to the surface receptors of the bacteria and directly inject the viral DNA into the bacteria.
Transduction happens in two ways: lytic cycle or lysogenic cycle. In the lytic cycle, the viral phage penetrates a host cell, destroys the host’s chromosome and replicates itself within the host cell. In the end, these phages destroy (lyse) the same host cell; hence, we call them virulent phages. Unlike in the lytic cycle, the direct lysis of the bacterial cell does not occur in the lysogenic cycle. In the lysogenic cycle, phage DNA integrates with the host chromosome as a prophage. After integration, the host cell undergoes DNA replication and binary fission, resulting in copies of the host cell with prophages. Finally, these prophages will excuse themselves from hosts’ chromosomes and go to the lytic cycle.
Figure 02: Transduction
Transduction is a useful tool in genetic engineering when introducing a foreign gene into bacteria. Also, it is useful to understand the mechanism by which antibiotic drugs become ineffective due to the transfer of antibiotic resistance genes between bacteria.
What are the Similarities Between Transformation and Transduction?
- Transformation and transduction are two mechanisms involved in horizontal gene transfer from one bacterium to another bacterium.
- These two mechanisms transfer DNA in one direction.
- However, both mechanisms transfer very few amounts of DNA and do not transfer the entire cell chromosome.
- Furthermore, both transformation and transduction are important tools in molecular biology and genetic engineering.
What is the Difference Between Transformation and Transduction?
Transformation is the genetic alteration of bacteria by direct uptake and incorporation of exogenous DNA from their surroundings. On the other hand, transduction is the process by which a virus transfers genetic material from one bacterium to another. So,this is the key difference between transformation and transduction. Transformation was discovered by Fred Griffith in 1928 while transduction was discovered by Norton Zinder and Joshua Lederberg in 1952. Moreover, the naked DNA moves across the wall and membrane of the recipient during the transformation without the aid of a virus. But, transduction is done by a bacteriophage. Therefore, we can consider this too as a difference between transformation and transduction.
Furthermore, in transformation, extracellular DNA fragments are acquired. In transduction, bacteriophage inserts DNA fragment into bacteria. Hence this is a significant difference between transformation and transduction. Additionally, a further difference between transformation and transduction is that a plasmid transfer is possible in transformation while it is not likely to occur in transduction. Above these, another significant difference between transformation and transduction is that the transformation is susceptible to DNAase while transduction is DNAase resistant.
Below infographic presents the difference between transformation and transduction as a side by side comparison.
Summary – Transformation vs Transduction
Transformation and transduction are two ways of horizontal gene transferring among bacteria. Transformation is the process of direct uptake of exogenous DNA from the surrounding via cell wall and membrane into the bacterial cell and incorporation to its genome. On the other hand, transduction is the process of injecting viral DNA into bacterial cells by the bacteriophages. Hence, transduction is done by a viral host. Furthermore, transformation occurs naturally and artificially. It depends on the competence of the bacteria. Transduction does not depend on the competence of the bacteria. Transduction occurs via lytic and lysogenic cycle. Thus, this is the difference between transformation and transduction.
Reference:
1. “5.1: Transformation in Bacteria.” Biology LibreTexts, Libretexts, 27 Nov. 2017, Available here.
2. Griffiths, Anthony JF. “Transduction.” An Introduction to Genetic Analysis. 7th Edition., U.S. National Library of Medicine, 1 Jan. 1970, Available here.
3. “Boundless Microbiology.” Lumen, Available here.
Image Courtesy:
1. “Artificial Bacterial Transformation” By Amunroe13 – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Transduction (genetics)en” By Reytan with modifications by Geni – modified version of Image:Transduction (genetics).svg (Public Domain) via Commons Wikimedia