Which of the following is NOT a mechanism that can mediate horizontal gene transfer?
Answer a. Surface adhesion b. Phage transduction c. Conjugation d. DNA transformation
The correct answer and explanation is:
The correct answer is a. Surface adhesion.
Horizontal gene transfer (HGT) is the process by which organisms, especially bacteria, acquire genetic material from other organisms. The main mechanisms of HGT include phage transduction, conjugation, and DNA transformation. These processes enable genetic diversity and adaptation in microorganisms.
- Phage transduction: This mechanism involves the transfer of genetic material from one bacterium to another through a bacteriophage (a virus that infects bacteria). When a bacteriophage infects a bacterium, it can incorporate a portion of the host’s DNA into its viral genome. When this virus infects another bacterium, it can transfer the genetic material to the new host.
- Conjugation: Conjugation is the process by which one bacterium transfers genetic material to another through direct contact. This typically occurs via a pilus, a thin, tube-like structure that forms between two bacteria. The donor bacterium often carries a plasmid, a small circular DNA molecule, which is transferred to the recipient bacterium.
- DNA transformation: In this process, a bacterium takes up free-floating genetic material (usually from the environment) through its cell membrane. This DNA can come from dead bacteria or from surrounding organisms. If the DNA is compatible, it may integrate into the recipient bacterium’s genome, potentially conferring new traits.
Surface adhesion refers to the ability of cells to adhere to surfaces, which is a critical process for establishing infections or biofilms. However, it is not a direct mechanism of horizontal gene transfer. Adhesion may assist in the proximity necessary for processes like conjugation or transformation, but it is not a gene transfer mechanism by itself.
Thus, surface adhesion is not a mechanism of horizontal gene transfer.