Transformation
By Chandana Valaboju | 7 September 2024
Bacterial Transformation is a process by which a bacterium takes up foreign DNA from its surroundings through the cell membrane, and integrates it into its own DNA. The foreign DNA material may be present as partially degraded fragments of dead cells or can be artificially introduced to it. For this process to occur, the bacterium cell must be in a state called "competent state" (that is, the cell membrane must be permeable), which, again, can occur naturally, or be artificially induced by physical chemical methods or electrical methods. The most common way of creating competent cells is by treating them with salts of divalent cations (such as calcium and magnesium chloride) followed by rapid heating and cooling (called heat shock).
Transformation was first discovered by Frederick Griffith in 1928, who observed that non-damaging bacteria could be ‘transformed’ into damage-inducing ones by exposing them to heat-killed strains of the latter.
It is believed that transformation occurs naturally to repair DNA damages, and it simultaneously generates genetic diversity. This phenomenon is exciting because it gives us a starting idea on how to achieve DNA cloning – since our desired gene can be replicated if introduced in a bacterium. In some cases, bacterial transformation can also be used to identify certain genes – because the introduced DNA can cause a mutation in the said gene, altering the characteristics of the bacterium which can be observed.
References:
- Johnston, C., Martin, B., Fichant, G. et al. Bacterial transformation: distribution, shared mechanisms and divergent control. Nat Rev Microbiol 12, 181–196 (2014). https://doi.org/10.1038/nrmicro3199
- Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002). Molecular Biology of the Cell. New York: Garland Science. p. G:35. ISBN 978-0-8153-4072-0.