Question

A virulence factor can be transferred from one strain of bacteria to another in a genetic process that is independent of cell-to-cell contact between the donor and the recipient. Addition of DNase does not interfere with the transfer of the virulence factor either. From these characteristics, which of the following processes is involved in this genetic transfer? A. Conjugation B. Transformation C. Transduction D. Transposition E. Transversion

Short answer

Based on the solution steps, the correct process involved in this genetic transfer is Transduction.

Step-by-step solution

- Analyze given options

We have five options: Conjugation, Transformation, Transduction, Transposition, and Transversion. Let's briefly analyze what each of them means. Conjugation is a mode of gene transfer in bacteria which requires cell-to-cell contact, hence this can't be the correct option. Transformation is a mode of gene transfer where the recipient bacterium takes up genetic material from its surrounding medium. Transduction involves transfer of genetic material from one bacterium to another via bacteriophages. Transposition involves movement of genetic elements called transposons within the genome. Lastly, Transversion is a type of point mutation.

- Evaluate the suitability of each option to the given scenario

From our preliminary analysis, it's clear that conjugation requires cell-to-cell contact, so it doesn't suit our scenario. Transduction also requires bacteriophages to conduct the transfer - but the problem doesn't mention this. Transposition and transversion are intra-genomic, meaning they occur within a single organism and don't involve transferring genes between organisms. This leaves us with Transformation - the process where a bacterium picks up genetic material from the medium surrounding it, which fits our given scenario.

- Check if the chosen process is affected by DNase

An important detail given in the problem is that the addition of DNase, an enzyme that degrades free DNA in the medium, doesn't interfere with the gene transfer. If our chosen process was transformation, then the addition of DNase would have inhibited its action as transformation involves the uptake of free DNA from the surroundings. Therefore, upon reevaluation, the process that fits the scenario perfectly isn't transformation, but it's Transduction because bacteriophages are not affected by DNase. The initial assessment was incorrect.

Key concepts

Transformation

In the fascinating world of bacterial genetics, transformation represents a crucial mechanism of genetic transfer. It's a process where a bacterium takes in DNA from its surrounding environment. What's remarkable here is that the DNA can come from different species, leading to genetic diversity.

During transformation, bacteria can incorporate stray fragments of DNA left behind from dead cells or released during cell lysis. These DNA pieces can then recombine with the bacterium’s own DNA, providing new characteristics to the bacterium, such as antibiotic resistance or increased virulence. However, in the context of the exercise, DNase, an enzyme that degrades DNA, does not affect the transfer. This detail is crucial because it suggests that transformation is not the correct answer, as DNase would inhibit the uptake of free DNA during this process.

Conjugation

Now let's delve into conjugation, a method of genetic exchange that could be likened to a bacterial 'handshake'. This intimate process requires physical contact between two bacterial cells. A donor cell extends a protrusion known as a pilus to connect with a recipient cell.

Through this connection, plasmids or other genetic elements can be transferred from the donor to the recipient, allowing them to share traits. This method is actually quite selective, requiring specific cell surface receptors to be present on both cells. Since the exercise specifies no cell-to-cell contact, conjugation is ruled out as the mechanism for our virulence factor's journey.

Transduction

Transduction is akin to a viral invasion in the bacterial world, where phages, or viruses that infect bacteria, hijack the genetic exchange. During this process, a bacteriophage infects a donor bacterium and accidentally incorporates segments of bacterial DNA into its own genome. When the phage later infects another bacterium, it injects not only its own genetic material but also the donor bacterium’s genes.

This accidental gene trafficking can lead to the recipient gaining new attributes, which could include virulence factors like those mentioned in the exercise. Crucially, DNase has no effect on transduction since the DNA is protected within the capsid of the bacteriophage, distinguishing it from transformation and supporting its role as the correct answer in the context of the problem provided.

Transposition

Transposition introduces us to the mobile elements of the bacterial genome known as transposons or 'jumping genes'. These are segments of DNA that can change their position within the genome, hopping from one location to another.

This action can be disruptive, causing mutations or changing the organism's traits by activating or deactivating genes. Transposition is a kind of genetic mobility within the confines of a single cell's genome, and thus, does not involve any exchange of genetic material between different bacteria. The exercise looks for a mechanism of gene transfer between bacteria, so transposition is not the appropriate answer here.

Transversion

Lastly, transversion is a term used to describe a particular kind of mutation at the molecular level. Specifically, it's a point mutation where a purine base (adenine or guanine) is replaced by a pyrimidine base (cytosine or thymine), or vice versa. This change can profoundly affect protein function if it occurs within a coding region.

While transversion can lead to changes in a single bacterium's genome, it is not a method of transferring genetic material between different bacteria. Consequently, in relation to the exercise scenario requiring the transfer of a virulence factor between bacteria, transversion is not the relevant process.