Transduction is the process by which foreign
DNA is introduced into a cell by a
virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's 1 ...
or
viral vector. An example is the viral transfer of DNA from one
bacterium
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
to another and hence an example of
horizontal gene transfer
Horizontal gene transfer (HGT) or lateral gene transfer (LGT) is the movement of genetic material between Unicellular organism, unicellular and/or multicellular organisms other than by the ("vertical") transmission of DNA from parent to offsprin ...
.
Transduction does not require physical contact between the cell donating the DNA and the cell receiving the DNA (which occurs in
conjugation
Conjugation or conjugate may refer to:
Linguistics
* Grammatical conjugation, the modification of a verb from its basic form
* Emotive conjugation or Russell's conjugation, the use of loaded language
Mathematics
* Complex conjugation, the chang ...
), and it is
DNase Deoxyribonuclease (DNase, for short) refers to a group of glycoprotein endonucleases which are enzymes that catalyze the hydrolytic cleavage of phosphodiester linkages in the DNA backbone, thus degrading DNA. The role of the DNase enzyme in cells ...
resistant (
transformation
Transformation may refer to:
Science and mathematics
In biology and medicine
* Metamorphosis, the biological process of changing physical form after birth or hatching
* Malignant transformation, the process of cells becoming cancerous
* Tran ...
is susceptible to DNase). Transduction is a common tool used by molecular biologists to stably introduce a foreign gene into a host cell's
genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...
(both bacterial and mammalian cells).
Discovery (bacterial transduction)
Transduction was discovered by
Norton Zinder
Norton David Zinder (November 7, 1928 – February 3, 2012) was an American biologist famous for his discovery of genetic transduction. Zinder was born in New York City, received his A.B. from Columbia University in 1947, Ph.D. from the Univers ...
and
Joshua Lederberg
Joshua () or Yehoshua ( ''Yəhōšuaʿ'', Tiberian: ''Yŏhōšuaʿ,'' lit. 'Yahweh is salvation') ''Yēšūaʿ''; syr, ܝܫܘܥ ܒܪ ܢܘܢ ''Yəšūʿ bar Nōn''; el, Ἰησοῦς, ar , يُوشَعُ ٱبْنُ نُونٍ '' Yūšaʿ ...
at the
University of Wisconsin–Madison
A university () is an educational institution, institution of higher education, higher (or Tertiary education, tertiary) education and research which awards academic degrees in several Discipline (academia), academic disciplines. Universities ty ...
in 1952 in Salmonella.
In the lytic and lysogenic cycles
Transduction happens through either the
lytic
The lytic cycle ( ) is one of the two cycles of viral reproduction (referring to bacterial viruses or bacteriophages), the other being the lysogenic cycle. The lytic cycle results in the destruction of the infected cell and its membrane. Bacter ...
cycle or the
lysogenic
Lysogeny, or the lysogenic cycle, is one of two cycles of viral reproduction (the lytic cycle being the other). Lysogeny is characterized by integration of the bacteriophage nucleic acid into the host bacterium's genome or formation of a circu ...
cycle.
When
bacteriophages (viruses that infect bacteria) that are lytic infect bacterial cells, they harness the
replicational,
transcriptional, and
translation
Translation is the communication of the Meaning (linguistic), meaning of a #Source and target languages, source-language text by means of an Dynamic and formal equivalence, equivalent #Source and target languages, target-language text. The ...
machinery of the host bacterial cell to make new viral particles (
virions
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's ...
). The new phage particles are then released by lysis of the host. In the lysogenic cycle, the phage chromosome is integrated as a
prophage into the bacterial chromosome, where it can stay dormant for extended periods of time. If the prophage is induced (by UV light for example), the phage genome is excised from the bacterial chromosome and initiates the lytic cycle, which culminates in
lysis
Lysis ( ) is the breaking down of the membrane of a cell, often by viral, enzymic, or osmotic (that is, "lytic" ) mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a ''lysate''. In molecular bio ...
of the cell and the release of phage particles. Generalized transduction (see below) occurs in both cycles during the lytic stage, while specialized transduction (see below) occurs when a prophage is excised in the lysogenic cycle.''
As a method for transferring genetic material
Transduction by bacteriophages
The packaging of bacteriophage DNA into phage capsids has low fidelity. Small pieces of bacterial DNA may be packaged into the bacteriophage particles. There are two ways that this can lead to transduction.
Generalized transduction
Generalized transduction occurs when random pieces of bacterial DNA are packaged into a phage. It happens when a phage is in the lytic stage, at the moment that the viral DNA is packaged into phage heads. If the virus replicates using 'headful packaging', it attempts to fill the head with genetic material. If the viral genome results in spare capacity, viral packaging mechanisms may incorporate bacterial genetic material into the new virion. Alternatively, generalized transduction may occur via
recombination. Generalized transduction is a rare event and occurs on the order of 1 phage in 11,000.
The new virus capsule that contains part bacterial DNA then infects another bacterial cell. When the bacterial DNA packaged into the virus is inserted into the recipient cell three things can happen to it:
# The DNA is recycled for spare parts.
# If the DNA was originally a
plasmid
A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; how ...
, it will re-circularize inside the new cell and become a plasmid again.
# If the new DNA matches with a homologous region of the recipient cell's chromosome, it will exchange DNA material similar to the actions in
bacterial recombination
Bacterial recombination is a type of genetic recombination in bacteria characterized by DNA transfer from one organism called donor to another organism as recipient. This process occurs in three main ways:
* Transformation, the uptake of exogeno ...
.
Specialized transduction
''Specialized transduction'' is the process by which a ''restricted'' set of bacterial genes is transferred to another bacterium. Those genes that are located adjacent to the prophage are transferred due to improper excision. Specialized transduction occurs when a prophage excises imprecisely from the chromosome so that bacterial genes lying adjacent to it are included in the excised DNA. The excised DNA along with the viral DNA is then packaged into a new virus particle, which is then delivered to a new bacterium when the phage attacks new bacterium. Here, the donor genes can be inserted into the recipient chromosome or remain in the cytoplasm, depending on the nature of the bacteriophage.
When the partially encapsulated phage material infects another cell and becomes a prophage, the partially coded prophage DNA is called a "heterogenote".
An example of specialized transduction is
λ phage
''Enterobacteria phage λ'' (lambda phage, coliphage λ, officially ''Escherichia virus Lambda'') is a bacterial virus, or bacteriophage, that infects the bacterial species ''Escherichia coli'' (''E. coli''). It was discovered by Esther Leder ...
in ''
Escherichia coli
''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escher ...
''.
Lateral transduction
''Lateral transduction'' is the process by which very long fragments of bacterial DNA are transferred to another bacterium. So far, this form of transduction has been only described in ''Staphylococcus aureus'', but it can transfer more genes and at higher frequencies than generalized and specialized transduction. In lateral transduction, the prophage starts its replication in situ before excision in a process that leads to replication of the adjacent bacterial DNA. After which, packaging of the replicated phage from its ''pac'' site (located around the middle of the phage genome) and adjacent bacterial genes occurs in situ, to 105% of a phage genome size. Successive packaging after initiation from the original ''pac'' site leads to several kilobases of bacterial genes being packaged into new viral particles that are transferred to new bacterial strains. If the transferred genetic material in these transducing particles provides sufficient DNA for homologous recombination, the genetic material will be inserted into the recipient chromosome.
Because multiple copies of the phage genome are produced during in situ replication, some of these replicated prophages excise normally (instead of being packaged in situ), producing normal infectious phages.
Mammalian cell transduction with viral vectors
![Synapsin and CamK2 positive neurons](https://upload.wikimedia.org/wikipedia/commons/b/bf/Synapsin_and_CamK2_positive_neurons.png)
Transduction with
viral vectors can be used to insert or modify genes in mammalian cells. It is often used as a tool in basic research and is actively researched as a potential means for
gene therapy
Gene therapy is a medical field which focuses on the genetic modification of cells to produce a therapeutic effect or the treatment of disease by repairing or reconstructing defective genetic material. The first attempt at modifying human DN ...
.
Process
In these cases, a plasmid is constructed in which the genes to be transferred are flanked by viral sequences that are used by viral proteins to recognize and package the viral genome into viral particles. This plasmid is inserted (usually by
transfection
Transfection is the process of deliberately introducing naked or purified nucleic acids into eukaryotic cells. It may also refer to other methods and cell types, although other terms are often preferred: " transformation" is typically used to des ...
) into a producer cell together with other
plasmid
A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; how ...
s (DNA constructs) that carry the viral genes required for the formation of infectious
virions
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's ...
. In these producer cells, the viral proteins expressed by these packaging constructs bind the sequences on the DNA/RNA (depending on the type of viral vector) to be transferred and insert it into viral particles. For safety, none of the plasmids used contains all the sequences required for virus formation, so that simultaneous transfection of multiple plasmids is required to get infectious virions. Moreover, only the plasmid carrying the sequences to be transferred contains signals that allow the genetic materials to be packaged in virions so that none of the genes encoding viral proteins are packaged. Viruses collected from these cells are then applied to the cells to be altered. The initial stages of these infections mimic infection with natural viruses and lead to expression of the genes transferred and (in the case of
lentivirus/retrovirus vectors) insertion of the DNA to be transferred into the cellular genome. However, since the transferred genetic material does not encode any of the viral genes, these infections do not generate new viruses (the viruses are "replication-deficient").
Some enhancers have been used to improve transduction efficiency such as
polybrene
Hexadimethrine bromide (commercial brand name Polybrene) is a cationic polymer with several uses. Currently, it is primarily used to increase the efficiency of transduction of certain cells with retrovirus in cell culture. Hexadimethrine bromi ...
,
protamine sulfate
Protamine sulfate is a medication that is used to reverse the effects of heparin. It is specifically used in heparin overdose, in low molecular weight heparin overdose, and to reverse the effects of heparin during delivery and heart surgery. ...
, retronectin, and DEAE Dextran.
Medical applications
*
Gene therapy
Gene therapy is a medical field which focuses on the genetic modification of cells to produce a therapeutic effect or the treatment of disease by repairing or reconstructing defective genetic material. The first attempt at modifying human DN ...
: Correcting genetic diseases by direct modification of genetic error.
See also
*
Electroporation
Electroporation, or electropermeabilization, is a microbiology technique in which an electrical field is applied to cells in order to increase the permeability of the cell membrane, allowing chemicals, drugs, electrode arrays or DNA to be introd ...
– use of an electrical field to increase cell membrane permeability.
*
Phage therapy
Phage therapy, viral phage therapy, or phagotherapy is the therapeutic use of bacteriophages for the treatment of pathogenic bacterial infections. This therapeutic approach emerged at the beginning of the 20th century but was progressively re ...
– therapeutic use of bacteriophages.
*
Signal transduction
Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events, most commonly protein phosphorylation catalyzed by protein kinases, which ultimately results in a cellula ...
*
Transfection
Transfection is the process of deliberately introducing naked or purified nucleic acids into eukaryotic cells. It may also refer to other methods and cell types, although other terms are often preferred: " transformation" is typically used to des ...
– means of inserting DNA into a cell.
*
Transformation (genetics)
In molecular biology and genetics, transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings through the cell membrane(s). For transformation to t ...
– means of inserting DNA into a cell.
*
Viral vector – commonly used tool to deliver genetic material into cells.
References
External links
*
Overview at ncbi.nlm.nih.gov* http://www.med.umich.edu/vcore/protocols/RetroviralCellScreenInfection13FEB2006.pdf (transduction protocol)
an
transduction at sdsu.edu
{{DEFAULTSORT:Transduction (Genetics)
Bacteriology
Bacteriophages
Modification of genetic information
Molecular biology
Virology