Eventually the cell lyses releasing the newly formed viral particles that can infect other bacteria. The integrated phage remains dormant until it is triggered to enter the lytic cycle. During both of these life cycles bacterial DNA can be accidentally packaged into the newly created phages. Transfer of this DNA to another cell is referred to as transduction. To do this scientists commonly use phagemids , a DNA cloning vector that contains both bacteriophage and plasmid properties. Scientists also use transduction to introduce foreign DNA into eukaryotic cells, like mammalian cell lines.
You can find all kinds of different lentiviral and AAV plasmids as well as ready-to-use viral preparations at Addgene. For more information on viral vectors, including transduction download our Viral Vectors eBook. Conjugation was the first extensively studied method of gene transfer and was discovered in by Joshua Lederberg and Edward Tatum when they observed genetic recombination between two nutritional deficient E.
During conjugation, genetic material is transferred from a donor bacterium to a recipient bacterium through direct contact. Once in contact the donor can transfer genetic material to the recipient bacterium. The genetic material transferred is commonly a plasmid and can infer genetic advantages such as antibiotic resistance. Typically the process requires a donor cell that at some point lysed and released naked DNA to the environment. The recipient cell is one that is capable of taking up the DNA from the environment and incorporating it into its own genome, where the cell is described as being competent.
There are mechanical and chemical means of encouraging a cell to pick up DNA from the environment, but natural competence is determined genetically.
The process typically occurs at the end of exponential phase of growth or beginning of the stationary phase, in the presence of high cell density and limited nutrients.
Under these conditions specific proteins are manufactured including DNA-binding proteins DNA translocase , endonucleases , and transmembrane channel proteins.
Gram negative cells also make a cell wall autolysin , to transport the DNA across the outer membrane.
Random pieces of DNA bind to receptors on the outside of the cell and are then transported into the cell by the DNA translocase, through the transmembrane channel, a large structure often involving numerous different proteins. Once inside the cell, the DNA must be incorporated into the bacterial chromosome by RecA see Molecular Recombination below , for the genes to be expressed. Transduction involves the use of a virus, a bacteriophage, to act as a conduit for shuttling bacteria genes from one cell to another, thus negating the necessity for cell-to-cell contact.
There are two different types of transduction: generalized transduction and specialized transduction. In generalized transduction, a bacterial host cell is infected with either a virulent or a temperate bacteriophage engaging in the lytic cycle of replication.
After the first three steps of replication absorption, penetration, and synthesis , the virus enters into the assembly stage, during which fully formed virions are made. During this stage, random pieces of bacterial DNA are mistakenly packaged into a phage head, resulting in the production of a transducing particle. While these particles are not capable of infecting a cell in the conventional sense, they can bind to a new bacterial host cell and inject their DNA inside.
Specialized transduction can only occur with temperate bacteriophage, since it involves the lysogenic cycle of replication. The bacteriophage randomly attaches to a bacterial host cell, injecting viral DNA inside. The DNA integrates into the chromosome of the host cell, forming a prophage. At some point induction occurs, where the prophage is excised from the bacterial chrosomsome.
Prokaryotes do not have the benefit of sexual reproduction, but they do still have the ability to increase genetic diversity through several types of gene transfer. One of the most important ways that prokaryotes especially bacteria engage in gene transfer is called transduction, and relies on the help of viruses. Prokaryotes are mostly unicellular organisms. They reproduce asexually through a process called binary fission. There are three kinds of gene transfer in prokaryotes that increase their genetic diversity.
They are transformation, conjugation and transduction. Transduction is important because of its implications for scientific research and bacterial antibiotic resistance.
Transduction happens when a virus uses a bacterium cell to replicate itself by hijacking it. This is because genetic material is not passed down from parent bacterial cells to offspring cells, but between bacterial cells of the same generation. The genetic information moves horizontally on the family tree, instead of vertically. Transduction was discovered in the s by microbiologists Norman Zinder and Joshua Lederberg as they studied salmonella.
It is one of the most important types of gene transfers, allowing bacterial DNA to move between cells. Viruses that infect bacteria, called bacteriophages, make transduction possible.
Since they move from one bacterial cell to another as infectious agents, they sometimes inadvertently grab up pieces of bacterial DNA from one host cell and deposit it in the next cell they bind to.
Viruses cannot reproduce on their own. Instead, they must use the more advanced reproductive cell biology of the bacteria to make copies of themselves. To do that, bacteriophages hijack host cells. When a bacteriophage encounters a bacterial cell , it binds to the cell and injects phage DNA through the plasma membrane into the cell. How could dead bacteria give genes to the live bacteria?
The dead one left DNA behind which was picked up by the alive bacteria, changing it so that it could kill. In transduction, genetic material is carried by a bacteriophage 'phage. Just imagine you would kiss somebody and thereby exchange genetic information with your mate, which helps you to survive under certain environmental conditions.
Well, this is exactly what bacteria cells are able to do and what is called conjugation. Scientifically, this term describes the transfer of genetic information from a donor bacterium to a recipient bacterium.
They have to establish a cytoplasm bridge for this task, so the cells have to be in direct contact.
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