How does a transposable element do the cutting and pasting? Does it use an enzyme from the cell or does it have its own enzyme?

Many§ transposable elements will encode a transposase — an enzyme to catalyze its movement to another location. The exact mechanisms vary among different types of transposons, but cutting and pasting is done by some of them. You can read more about this in these wikipedia articles: https://en.wikipedia.org/wiki/Transposase https://en.wikipedia.org/wiki/Transposable_element §Note that transposons can also have parasites — these are known as non-autonomous transposons. They tend to be smaller versions of the autonomous transposons and "steal" the enzyme produced by autonomous transposons to move themselves.

What is the relationship between a sex pilus and a mating bridge?

A mating bridge is a connection between two bacterial cells that provides a passageway for DNA in bacterial conjugation. A mating bridge is different from a sex pilus, which is a structure made by an F+ strain bacterium in bacterial conjugation Sex pilus acts as an attachment site that promotes the binding of bacteria to each other. In this way, an F+ strain makes physical contact with an F− strain. Once contact is made, the pili shorten and thereby draw the donor and recipient cells closer together. A conjugation bridge is then formed between the two cells, which provides a passageway for DNA transfer.

In prokaryotes, is the plasmid the only genetic material may be copied and passed to daughter cells? This article seems to say so, but isn't bacterial DNA may also be passed to daughter cells as well?

I just read the article and it isn't saying that — chromosomal DNA is definitely passed on to the daughter cells. Have another look at the first figure — that clearly shows the daughter cell as having both the plasmid (blue) and chromosomal (pink) DNA.

can HFr conjugation increase bacterial diversity?

Because that is a way of horizontal transfer of chromosomes, and genetic material from other bacteria suddenly ends up in new bacteria. https://www.ncbi.nlm.nih.gov/books/NBK7908/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5478984/ https://bio.libretexts.org/Bookshelves/Microbiology/Book%3A_Microbiology_(Kaiser)/Unit_2%3A_Bacterial_Genetics_and_the_Chemical_Control_of_Bacteria/3%3A_Bacterial_Genetics/3.1%3A_Horizontal_Gene_Transfer_in_Bacteria https://mmbr.asm.org/content/mmbr/29/2/161.full.pdf

during conjugation the bacterium that donates its genes to another bacteria may become deficient for those genes how they survive ?

Typically, the donor bacterium makes a copy of the DNA that is being transferred, so there is no loss. See this wikipedia article for a clear diagram: https://en.wikipedia.org/wiki/Bacterial_conjugation#Mechanism

Main content

Course: Biology library > Unit 23

Lesson 1: Prokaryote structure

Genetic variation in prokaryotes

Google Classroom

Mechanisms that generate variation in prokaryote populations. Transduction, transformation, conjugation, transposable elements.

Key points:

In transformation, a bacterium takes up a piece of DNA floating in its environment.
In transduction, DNA is accidentally moved from one bacterium to another by a virus.
In conjugation, DNA is transferred between bacteria through a tube between cells.
Transposable elements are chunks of DNA that "jump" from one place to another. They can move bacterial genes that give bacteria antibiotic resistance or make them disease-causing.

Introduction

When you hear the word "clone," what do you think of? Maybe Dolly the sheep, or experiments carried out in molecular biology labs. But it's also true that the bacteria around you—on your skin, in your gut, growing on your kitchen sink—are "cloning" themselves all the time!

Bacteria reproduce by splitting in two via binary fission. Binary fission makes clones, or genetically identical copies, of the parent bacterium. Since the "child" bacteria are genetically identical to the parent, binary fission doesn't provide an opportunity for genetic recombination or genetic diversity (aside from the occasional random mutation). This contrasts with sexual reproduction.

Still, genetic variation is key to the survival of a species, allowing groups to adapt to changes in their environment by natural selection. That's true for bacteria as well as plants and animals. So it's not too surprising that prokaryotes can share genes by three other mechanisms: conjugation, transformation, and transduction.

Transformation

In transformation, a bacterium takes in DNA from its environment, often DNA that's been shed by other bacteria. In a laboratory, the DNA may be introduced by scientists (see biotechnology article). If the DNA is in the form of a circular DNA called a plasmid, it can be copied in the receiving cell and passed on to its descendants.

Why would this be important? Imagine that a harmless bacterium takes up DNA for a toxin gene from a pathogenic (disease-causing) species of bacterium. If the receiving cell incorporates the new DNA into its own chromosome (which can happen by a process called homologous recombination), it too may become pathogenic.

Transduction

In transduction, viruses that infect bacteria move short pieces of chromosomal DNA from one bacterium to another "by accident."

Yep, even bacteria can get a virus! The viruses that infect bacteria are called bacteriophages. Bacteriophages, like other viruses, are the pirates of the biological world—they commandeer a cell's resources and use them to make more bacteriophages.

However, this process can be a little sloppy. Sometimes, chunks of host cell DNA get caught inside the new bacteriophage as they are made. When one of these "defective" bacteriophages infects a cell, it transfers the DNA. Some bacteriophages chop the DNA of their host cell into pieces, making this transfer process more likely

^{1}

Archaea, the other group of prokaryotes besides bacteria, are not infected by bacteriophages but have their own viruses that move genetic material from one individual to another.

Conjugation

In conjugation, DNA is transferred from one bacterium to another. After the donor cell pulls itself close to the recipient using a structure called a pilus, DNA is transferred between cells. In most cases, this DNA is in the form of a plasmid.

Image modified from "Conjugation," by Adenosine (CC BY-SA 3.0). The modified image is licensed under a CC BY-SA 3.0 license.

Donor cells typically act as donors because they have a chunk of DNA called the fertility factor (or F factor). This chunk of DNA codes for the proteins that make up the sex pilus. It also contains a special site where DNA transfer during conjugation begins

^{2}

If the F factor is transferred during conjugation, the receiving cell turns into an F

^{+}

donor that can make its own pilus and transfer DNA to other cells. Here's one analogy: this process is sort of like how a vampire can turn other people into vampires by biting them.

Transposable elements

Transposable elements are also important in bacterial genetics

^{3}

. These chunks of DNA "jump" from one place to another within a genome, cutting and pasting themselves or inserting copies of themselves in new spots. Transposable elements are found in many organisms (including you and me!), not just in bacteria.

In bacteria, transposable elements sometimes carry antibiotic resistance and pathogenicity genes (genes that make bacteria disease-causing)

^{4, 5, 6}

. If one of these transposable elements "jumps" from the chromosome into a plasmid, the genes it carries can be easily passed to other bacteria by transformation or conjugation. That means the genes can spread quickly through the population.

Conclusion

In bacteria, reproduction can be very fast, with a generation taking little more than a few minutes for some species. This short generation time, together with random mutations and the mechanisms of genetic recombination we saw in this article, allow bacteria (and other prokaryotes) to evolve very quickly.

Is that a good thing? It depends on your perspective. Rapid evolution means that bacteria can adapt to environmental changes, such as the introduction of an antibiotic, very quickly. That's good for them—but bad for us, when we are the ones with the infection!

In a population of bacteria, there might be a version (allele) of a particular gene in the bacterial chromosome that gives resistance to an antibiotic. If there is no antibiotic around, this allele may remain uncommon in the population (found in only a few of the many bacteria), since it does not give the bacteria that carry it an advantage in survival or reproduction.

However, if antibiotic is added to the bacteria's environment, most of the bacteria will be killed. The only ones that survive will be those with the antibiotic-resistant allele, which they'll pass on to their offspring (who will also be resistant). In the next generation, all of the bacteria in the population will have the antibiotic resistance allele and be able to survive in the antibiotic-containing environment.

As these bacteria multiply, they will replace the ones that died, bringing the population back to its normal size. Thanks to genetic variation, the population as a group has survived the "catastrophe" of the antibiotic and adapted to the new situation.

You can also imagine the case where the antibiotic resistance allele is transferred to a plasmid—say, by a jumping transposable element. In that case, the resistance trait could also be passed directly from one bacterium to another, unrelated bacterium through conjugation.

Attribution:

This article is a modified derivative of "Structure of prokaryotes," by OpenStax College, Biology, CC BY 4.0. Download the original article for free at http://cnx.org/contents/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.53.

This article is licensed under a CC BY-NC-SA 4.0 license.

Works cited:

Griffiths, A. J. F., Miller, J. H., Suzuki, D. T., Lewontin, R. C., and Gelbart, W. M. (2000). Transduction. In An introduction to genetic analysis (7th ed.). New York, NY: W. H. Freeman. Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK21760/#_A1365_.
Firth, N., Ippen-Ihler, K., and Skurray, R. A. (n.d.). Structure and function of the F factor and mechanism of conjugation. In Biology 105M - Microbial genetics lab. Retrieved from http://bio.classes.ucsc.edu/bio105l/EXERCISES/F%20TRANSFER/Chap126.pdf.
Purves, W.K., Sadava, D., Orians, G.H., and Heller, H.C. (2003). The genetics of viruses and prokaryotes. In Life: The science of biology (7th ed., p. 269). Sunderland, MA: Sinauer Associates, Inc.
Bennett, P. M. (2008). Plasmid encoded antibiotic resistance: acquisition and transfer of antibiotic resistance genes in bacteria. Br. J. Pharmacol., 153(Suppl. 1), S349-S351. http://dx.doi.org/10.1038/sj.bjp.0707607.
Gyles, C. and Boerlin, P. (2014). Horizontally transferred genetic elements and their role in the pathogenesis of bacterial disease. Veterinary Pathology, 51(12), 330-322. https://www.ncbi.nlm.nih.gov/pubmed/24318976.
Purves, W.K., Sadava, D., Orians, G.H., and Heller, H.C. (2003). The genetics of viruses and prokaryotes. In Life: The science of biology (7th ed., p. 269). Sunderland, MA: Sinauer Associates, Inc.
Campbell, N. A., Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., and Jackson, R. B. (2009). Transposable elements and related sequences. In Campbell biology (8th ed., p. 435). San Francisco, CA: Pearson.

Additional references:

Bacterial conjugation. (2003, March 18). In Physics forums. Retrieved March 2, 2016 from https://www.physicsforums.com/threads/bacterial-conjugation.129/.

Bacterial conjugation. (2016, April 9). Retrieved April 19, 2016 from Wikipedia: https://en.wikipedia.org/wiki/Bacterial_conjugation.

Bacterial growth. (2015, December 31). Retrieved March 2, 2016 from Wikipedia: https://en.wikipedia.org/wiki/Bacterial_growth.

Bennett, P. M. (2008). Plasmid encoded antibiotic resistance: acquisition and transfer of antibiotic resistance genes in bacteria. Br. J. Pharmacol., 153(Suppl. 1), S347-S357. http://dx.doi.org/10.1038/sj.bjp.0707607.

Campbell, N. A., Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., and Jackson, R. B. (2009). Transposable elements and related sequences. In Campbell biology (8th ed., p. 435-436). San Francisco, CA: Pearson.

Firth, N., Ippen-Ihler, K., and Skurray, R. A. (n.d.). Structure and function of the F factor and mechanism of conjugation. In Biology 105M - Microbial genetics lab. Retrieved from http://bio.classes.ucsc.edu/bio105l/EXERCISES/F%20TRANSFER/Chap126.pdf.

Griffiths, A. J. F., Miller, J. H., Suzuki, D. T., Lewontin, R. C., and Gelbart, W. M. (2000). Bacterial conjugation. In An introduction to genetic analysis (7th ed.). New York, NY: W. H. Freeman. Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK21942/.

Griffiths, A. J. F., Miller, J. H., Suzuki, D. T., Lewontin, R. C., and Gelbart, W. M. (2000). Transduction. In An introduction to genetic analysis (7th ed.). New York, NY: W. H. Freeman. Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK21760.

Grohmann, E., Muth, G., and Espinosa, M. (2003). Conjugative plasmid transfer in gram-positive bacteria. Microbiol. Mol. Biol. Rev., 67(2), 277-301. http://dx.doi.org/10.1128/MMBR.67.2.277-301.2003

Gyles, C. and Boerlin, P. (2014). Horizontally transferred genetic elements and their role in the pathogenesis of bacterial disease. Veterinary Pathology, 51(12), 328-340. https://www.ncbi.nlm.nih.gov/pubmed/24318976.

Kimball, J. W. (2015, April 18). Transposons: Mobile DNA. In Kimball's biology pages. Retrieved from http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Transposons.html#Transposons_in_Bacteria.

Lodish, H., Berk, A., Zipursky S. L., et al. (2000). Mutations: Types and causes. InMolecular cell biology. (4th ed., section 8.1). New York, NY: W. H. Freeman. Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK21578/.

Pilus. (2016, February 13). Retrieved March 2, 2016 from Wikipedia: https://en.wikipedia.org/wiki/Pilus

Purves, W. K., Sadava, D., Orians, G. H., and Heller, H. C. (2003). Bacteria and archaea: The prokaryotic domains. In Life: The science of biology (7th ed., pp. 524-542). Sunderland, MA: Sinauer Associates, Inc.

Purves, W.K., Sadava, D., Orians, G.H., and Heller, H.C. (2003). The genetics of viruses and prokaryotes. In Life: The science of biology (7th ed., pp. 257-277). Sunderland, MA: Sinauer Associates, Inc.

Raven, P. H., Johnson, G. B., Mason, K. A., Losos, J. B., and Singer, S. R. (2014). Conjugation depends on the presence of a conjugative plasmid. In Biology (10th ed., AP ed., pp. 548-550). New York, NY: McGraw-Hill.

Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., and Jackson, R. B. (2011). Bacteria and archaea. In Campbell biology (10th ed., pp. 567-575). San Francisco, CA: Pearson.

Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., and Jackson, R. B. (2011). Transposable elements and related sequences. In Campbell biology (10th ed., pp. 444-445). San Francisco, CA: Pearson.

Todar, K. (2012) The growth of bacterial populations (page 3). In Todar's online textbook of bacteriology. Retrieved from http://textbookofbacteriology.net/growth_3.html.

Check your understanding

Match each type of gene transfer with its definition.
$1$ ‍
In transformation, prokaryotes take up DNA directly from their environment (either as a circular plasmid, or as a DNA fragment that can integrate into the prokaryote's genome through homologous recombination).
During transduction, a virus transfers DNA from one prokaryote to another. Viruses that infect bacteria (bacteriophages) can accidentally pick up DNA from host bacteria during the production of new viral particles, then inject this bacterial DNA into the cell they infect.
During conjugation, one prokaryote transfers DNA directly to another prokaryote through a structure called a mating bridge, a process that requires physical contact between the two cells.

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ceece15
Posted 8 years ago. Direct link to ceece15's post “How does a transposable e...”
How does a transposable element do the cutting and pasting? Does it use an enzyme from the cell or does it have its own enzyme?
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- tyersome
  Posted 6 years ago. Direct link to tyersome's post “Many§ transposable elemen...”
  Many§ transposable elements will encode a transposase — an enzyme to catalyze its movement to another location. The exact mechanisms vary among different types of transposons, but cutting and pasting is done by some of them.
  
  You can read more about this in these wikipedia articles:
  https://en.wikipedia.org/wiki/Transposase
  https://en.wikipedia.org/wiki/Transposable_element
  
  §Note that transposons can also have parasites — these are known as non-autonomous transposons. They tend to be smaller versions of the autonomous transposons and "steal" the enzyme produced by autonomous transposons to move themselves.
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  (5 votes)
lipsadhrua321
Posted 7 years ago. Direct link to lipsadhrua321's post “What is generalized and s...”
What is generalized and specialized transduction?
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- rhea ♡
  Posted a year ago. Direct link to rhea ♡'s post “In generalized transducti...”
  In generalized transduction, the bacteriophages can pick up any portion of the host's genome. In contrast, with specialized transduction, the bacteriophages pick up only specific portions of the host's DNA.
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  (1 vote)
Ka Yu WONG
Posted 5 years ago. Direct link to Ka Yu WONG's post “What is the relationship ...”
What is the relationship between a sex pilus and a mating bridge?
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(3 votes)
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- Ivana - Science trainee
  Posted 5 years ago. Direct link to Ivana - Science trainee's post “A mating bridge is a conn...”
  A mating bridge is a connection between two bacterial cells that provides a passageway for DNA in bacterial conjugation.
  A mating bridge is different from a sex pilus, which is a structure made by an F+ strain bacterium in bacterial conjugation
  
  Sex pilus acts as an attachment site that promotes the binding of bacteria to each other. In this way, an F+ strain makes physical contact with an F− strain. Once contact is made, the pili shorten and thereby draw the donor and recipient cells closer together. A conjugation bridge is then formed between the two cells, which provides a passageway for DNA transfer.
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  (3 votes)
Anshari Hasanbasri
Posted 6 years ago. Direct link to Anshari Hasanbasri's post “In prokaryotes, is the pl...”
In prokaryotes, is the plasmid the only genetic material may be copied and passed to daughter cells? This article seems to say so, but isn't bacterial DNA may also be passed to daughter cells as well?
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(2 votes)
Answer
- tyersome
  Posted 6 years ago. Direct link to tyersome's post “I just read the article a...”
  I just read the article and it isn't saying that — chromosomal DNA is definitely passed on to the daughter cells.
  
  Have another look at the first figure — that clearly shows the daughter cell as having both the plasmid (blue) and chromosomal (pink) DNA.
  Comment on tyersome's post “I just read the article a...”
  (2 votes)
Sierra Enea
Posted 4 years ago. Direct link to Sierra Enea's post “can HFr conjugation incre...”
can HFr conjugation increase bacterial diversity?
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(2 votes)
Answer
- Ivana - Science trainee
  Posted 4 years ago. Direct link to Ivana - Science trainee's post “Because that is a way of ...”
  Because that is a way of horizontal transfer of chromosomes, and genetic material from other bacteria suddenly ends up in new bacteria.
  
  https://www.ncbi.nlm.nih.gov/books/NBK7908/
  
  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5478984/
  https://bio.libretexts.org/Bookshelves/Microbiology/Book%3A_Microbiology_(Kaiser)/Unit_2%3A_Bacterial_Genetics_and_the_Chemical_Control_of_Bacteria/3%3A_Bacterial_Genetics/3.1%3A_Horizontal_Gene_Transfer_in_Bacteria
  https://mmbr.asm.org/content/mmbr/29/2/161.full.pdf
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  (2 votes)
maimoona643
Posted 5 years ago. Direct link to maimoona643's post “during conjugation the ba...”
during conjugation the bacterium that donates its genes to another bacteria may become deficient for those genes how they survive ?
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(2 votes)
Answer
- tyersome
  Posted 5 years ago. Direct link to tyersome's post “Typically, the donor bact...”
  Typically, the donor bacterium makes a copy of the DNA that is being transferred, so there is no loss.
  
  See this wikipedia article for a clear diagram:
  https://en.wikipedia.org/wiki/Bacterial_conjugation#Mechanism
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  (2 votes)
NAOMI MOSIMANEGAPE
Posted 4 years ago. Direct link to NAOMI MOSIMANEGAPE's post “so we can take the dna as...”
so we can take the dna as if its like all the other substances taken in by cells through their cell membrane?
and also under conjugation when the virus invades the bacterial cell it takes the dna of the host as if it is its own ?
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(2 votes)
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Han
Posted 5 years ago. Direct link to Han's post “What is homologous recomb...”
What is homologous recombination? ("the receiving cell incorporates the new DNA into its own chromosome (which can happen by a process called homologous recombination)")
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eunbee
Posted 2 years ago. Direct link to eunbee's post “Is bacterial conjugation ...”
Is bacterial conjugation only for transfer of F plasmids or any kind of plasmid?
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MLSofa
Posted 5 years ago. Direct link to MLSofa's post “In the transduction part:...”
In the transduction part: When they say the virus passes genetic information from one bacteria to another "by accident", what does it exactly mean by that? Because I read in another article that didn't say that this occurs "by accident".
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