If the lysogen 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 of the cell and the release of phage particles. The lytic cycle leads to the production of new phage particles which are released by lysis of the host.
Transduction is a method for transferring genetic material. The packaging of bacteriophage DNA has low fidelity and small pieces of bacterial DNA, together with the bacteriophage genome, may become packaged into the bacteriophage genome. At the same time, some phage genes are left behind in the bacterial chromosome. There are generally three types of recombination events that can lead to this incorporation of bacterial DNA into the viral DNA, leading to two modes of recombination.
Generalized transduction is the process by which any bacterial gene may be transferred to another bacterium via a bacteriophage, and typically carries only bacterial DNA and no viral DNA.
In essence, this is the packaging of bacterial DNA into a viral envelope. This may occur in two main ways, recombination and headful packaging. If by chance bacterial chromosomal DNA is inserted into the viral capsid which is usually used to encapsulate the viral DNA, the mistake will lead to generalized transduction. If the viral genome results in spare capacity, viral packaging mechanisms may incorporate bacterial genetic material into the new virion.
The new virus capsule, now loaded with part bacterial DNA, continues to infect another bacterial cell. This bacterial material may become recombined into another bacterium upon infection. This type of recombination is random and the amount recombined depends on the size of the virus being used. Once inside, phages can follow one of two different life cycles: lytic or lysogenic. Lytic phages hijack the bacterial hosts machinery to make more viral particles. 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. Unlike the last three methods which can be used in prokaryotes, transfection is only done in eukaryotic cells.
Transfection is the process by which foreign DNA is deliberately introduced into a eukaryotic cell through non-viral methods including both chemical and physical methods in the lab. Chemicals like calcium phosphate and diethylaminoehtyl DEAE -dextra neutralize or even impart an overall positive charge on DNA molecules so that it can more easily cross the negatively charged cell membrane. Physical methods such as electroporation or microinjection actually pokes holes in the cell membrane so DNA can be introduced directly into the cell.
Microinjection requires the use of a fine needle to deliver nucleic acids to individual cells. Electroporation on the other hand uses electrical pulses to create transient pores in the cell membrane that genetic material can pass through.
Baltrus, David A. Bacterial Conjugation. In An Introduction to Genetic Analysis. Meibom, Karin L. Topics: Plasmids , Plasmids.
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