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Bacterial Genetic Recombination via Conjugation

Duration: 16:30

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In this fascinating mechanism review, we will learn about the self-replicating plasmid transfer from a male/donor bacterium to a female/recipient bacterium. We will review the structure and function of plasmids. Bacterial structure. Types of male/donor bacteria. That is, F+ or male, F' or F prime male, High frequency recombination cells or Hfr bacterium. Finally, we will discuss the details of the conjugation mechanism.

What is an “F” Plasmid?   How does it help bacteria to reproduce?  And what transformation happens next?

Conjugation is the transfer of a copy of a plasmid from one bacterium to another. 

A Plasmid is an extra chromosomal double stranded DNA piece present in a bacterium usually in the form of a circular structure.

A plasmid can replicate without the need for replication of the bacterial chromosome. 

A plasmid must contain all the genes which encode the proteins and enzymes that would allow a copy of this plasmid to be transferred from one bacteria to the next.  They are called self-replicating plasmids, or conjugative plasmids, or fertility plasmids or simply F Plasmids (F for fertility…of course!)

Many plasmids do not have the ability to self-replicate, although they can replicate along with the bacteria.  

This discussion is limited to the F Plasmids.

TC 2:33

Some of the genes that are important for replication:

  • *TRA or transference gene. This gene encodes a gene that helps in transferring a strand of the DNA from this plasmid to the next bacterium;

  • *MOB gene- aka mobility gene - mobilizes the plasmid to prepare for the transfer;

  • *oriT - origin of transfer gene - where the transfer process starts from;

  • *Genes for producing exotoxins or drug resistance, or some other “value added” property.

TC 4.05

Review of a bacterium structure:

  • *Capsule + cell wall + Plasma membrane. In conjugation, the sex pilus must penetrate all these layers into the cytoplasm containing:

  • *Nucleoid structure containing the chromosomes;

  • *Double-stranded plasmids, some of which are self-replicative;

  • *Ribosomes that pick up a gene’s mRNA and translate it into a protein.

  • *In addition there are fimbriae and pili, and some bacteria have flagella.

TC 5:56

Donor bacteria come in 3 types depending on the genetic material’s structure and its integration with the bacterial chromosome

  • *Male bacterium, or F+

  • *F prime

  • *High Frequency recombination cells, or HFR

Any bacterium that doesn’t contain a self-replicating plasmid is called a female (F-). If it contains a self replicating plasmid it is called a male (F+) 

In an F Prime bacteria a piece of the chromosome has become incorporated into the plasmid which is then carried with the plasmid to the next bacterium bringing a part of the bacterial DNA with it.

In a high-frequency recombination bacteria (HFR), the chromosome has incorporated a complete self-replicative plasmid into its structure and the whole thing, including the F plasmid, will transfer to the recipient cell. 

TC 10:07

How will the plasmid replicate?

  • *MOB gene starts the process of creating the Mob Protein.

  • *MOB Protein will cause a break at the oriT;

  • *TRA protein’s job is to assemble a sex pilus from the bacterium with the F plasmid to the next bacterium, and pull the bacteria closer together to allow the transfer of the plasmid material.  In this process the pilus contracts to become a pore between the two cells

  • *Now the strands of the F+ plasmids separate, and one strand stays behind in the F+ bacteria and the other travels through the pilus “pore” into the F- bacterium, where it will be recircularized. Now both the bacteria have a single strand of plasmid in them.

  • *The “Pore” disappears, and enzymes complete the other strand of plasmid, so both now have a self-replicating plasmid.

  • *The process transformed the F- bacteria into an F+ bacteria.

  • *It is a similar process for F Prime or HFR plasmids as well, in which they carry the characteristics of that plasmid (i.e.cytotoxicity or drug resistance) and confer them to the recipient bacterium.

And that is how bacteria have sex!

See you at the next lecture!

* Key genes involved in bacterial conjugation: Tra gene, mob gene, and OriT gene.

* Function of plasmids in carrying exotoxins and drug resistance genes.

* Structural components of bacteria: pilus, ribosomes, flagellum, capsule, cell wall, plasma membrane, plasmid, and nucleoid chromosome.

* Differentiation between male (F+) and female (F-) bacteria based on plasmid possession.

* Concepts of F prime plasmids and Hfr cells in conjugation.

* Process of conjugation: sex pilus formation, DNA transfer, recircularization, and plasmid replication.

Following answers are created by ChatGPT. Occasionally the answer may be harmful, incorrect, false, misleading, incomplete, or limited in knowledge of world. Please contact your doctor for all healthcare decisions. Also, double check the answer provided by the AI below.


In addition to the presenter, following authors may have helped with the content writing, review, or approval:

  • Dr. Mobeen Syed

CME, CE, CEU and Other Credit Types:

ACCME Accreditation Statement
The DrBeen Corp is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.

AMA Credit Designation Statement
The DrBeen Corp designates this enduring material for a maximum of 0.25 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

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In accordance with the disclosure policies of DrBeen Corp and the ACCME (Accreditation Council for Continuing Medical Education), we are committed to upholding principles of balance, independence, objectivity, and scientific rigor in all of our Continuing Medical Education (CME) and Continuing Education (CE) activities. These policies include the careful management and mitigation of any relevant financial relationships with organizations that are not eligible.
All members of the Activity Planning Committee and presenters have disclosed their relevant financial relationships. The DrBeen Corp CE Committee has thoroughly reviewed these disclosures and determined that these relationships are not deemed inappropriate in the context of their respective presentations. Additionally, they are found to be consistent with the educational objectives and the integrity of the activity.

Faculty Disclosures
Dr. Mobeen Syed Author declares no conflict of interest.

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Dr. Mobeen Syed

Dr. Mobeen Syed

MD., MSc., MSc., BSc

Mobeen Syed is the CEO of DrBeen Corp, a modern online medical education marketplace. Mobeen is a medical doctor and a software engineer. He graduated from the prestigious King Edward Medical University Lahore. He has been teaching medicine since 1994. Mobeen is also a software engineer and engineering leader. In this role, Mobeen has run teams consisting of hundreds of engineers and millions of dollars of budgets. Mobeen loves music, teaching, and doing business. He lives in Cupertino CA.


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