Question

A male bacterium conjugates with a female bacterium. After conjugation, the female becomes a male. Account for this "sex change".

Short answer

In bacterial conjugation, a male donor bacterium transfers its conjugative plasmid to a female recipient bacterium. After receiving the plasmid, the recipient bacterium gains the necessary genetic material to produce a sex pilus. This results in the recipient bacterium undergoing a "sex change," as it can now initiate conjugation like a male bacterium.

Step-by-step solution

Understand Bacterial Conjugation

Bacterial conjugation is a mechanism for the horizontal transfer of genetic material between two bacterial cells. One bacterium, referred to as the donor (male) contains a sex pilus and a conjugative plasmid. The other bacterium, referred to as the recipient (female), lacks both the sex pilus and the conjugative plasmid. During conjugation, the sex pilus of the donor attaches to the recipient, establishing the necessary connection for transferring genetic material.

Transfer of Genetic Material

In the process of conjugation, the donor bacterium transfers a copy of its conjugative plasmid to the recipient bacterium. The original plasmid remains within the donor bacterium, while the recipient receives a replicated copy. The conjugative plasmid contains genes responsible for the production of the sex pilus and other functions necessary for conjugation.

Formation of Sex Pilus in the Recipient

Following the receipt of the conjugative plasmid, the recipient bacterium now contains the necessary genetic information to produce a sex pilus. The recipient bacterium's genetic material has effectively been altered by acquiring the newly gained genetic information, allowing for the formation of a sex pilus.

Sex Change in Bacterial Conjugation

Since the recipient (female) bacterium obtains the genetic material necessary for forming a sex pilus and has effectively turned into a donor bacterium, it is considered to have undergone a "sex change". The recipient bacterium, originally female, is now capable of initiating conjugation, functioning as a male bacterium.

Key concepts

Genetic Material Transfer

In the world of bacteria, genetic material transfer is a fascinating process that enables them to share genes. Conjugation is a primary method allowing two bacterial cells to exchange genetic information. Unlike sexual reproduction in higher organisms, this does not involve the fusion of gametes. Instead, it is more like sharing a piece of genetic software.

• A donor, often referred to as the "male," initiates the process with a sex pilus.
• The recipient, known as the "female," lacks this structure and awaits the genetic transfer.

During bacterial conjugation, genetic material, specifically the conjugative plasmid, is transferred from the donor to the recipient. This transfer, although not altering the chromosomes, can significantly change the recipient's capabilities.
This method of genetic material transfer is akin to passing down instructions without changing the entire DNA blueprint. The recipient gains new genetic traits, such as antibiotic resistance or other survival advantages.

Conjugative Plasmid

The central player in bacterial conjugation is the conjugative plasmid. This is a small DNA molecule within a bacterium that is separate from chromosomal DNA.

• Conjugative plasmids carry the genes that code for pilus formation and other proteins essential for the conjugation process.
• They have the ability to replicate independently of the bacterial chromosome.

When a donor bacterium transfers the conjugative plasmid to a recipient, it's much like offering a toolkit. This tool kit carries vital pieces of DNA that prepare the recipient to become a donor itself.
The conjugative plasmid facilitates this transformation, allowing the recipient to form a sex pilus and take on a new role in the bacterial world. Essentially, the plasmid is the key to understanding how the "female" turns "male" after conjugation.

Sex Pilus Formation

The formation of a sex pilus is a crucial step in the bacterial conjugation process. This hair-like structure extends from the surface of the donor cell to make contact with the recipient.

• The sex pilus acts as a bridge, establishing direct contact between the donor and recipient cells.
• It is a product of the genes carried by the conjugative plasmid.

Once the recipient bacterium receives the conjugative plasmid, it acquires the genetic blueprint needed to produce a sex pilus. This transformation allows the recipient to engage in further conjugation as a donor.
The formation of a sex pilus is not merely a structural modification; it symbolizes the bacterium's new genetic capabilities. This ability to create a pilus highlights the flexibility and adaptability of bacterial genetics, allowing them to thrive in diverse environments.