Feb 09, · A bacterial plasmid is a strand of DNA inside a bacterium which is independent of the bacterium's chromosomal DNA. Plasmids are capable of replicating on their own, and they can be passed between organisms, an important trait for bacteria, as they use plasmids to transfer genetic information between each other. Plasmids are usually circular molecules of DNA, although occasionally, plasmids that are linear or made of RNA exist. They may be found as single or multiple copies and may carry from half a dozen to several hundred genes. Plasmids can only multiply inside a host cell.
Plasmids are capable of replicating plaemids their own, and they can be passed between organisms, an important trait for bacteria, as they use plasmids to transfer genetic information between each other. This ability also becomes important for researchers, who use bacterial plasmids as vectors to insert foreign DNA into DNA they are researching. The structure of a plasmid is often double stranded and circular.
It can contain a varying length of genetic information, and there are several different kinds of plasmids which can perform different functions. Some, for example, can perform conjugation, connecting with another bacterium to transfer genetic information. Others carry genetic information which confers antibiotic resistance, helps a bacterium break down nutrients to make them accessible, or makes the bacterium virulent. These plasmids cannot conjugate on their own; they need help how to teach scientific notation a conjugating plasmid.
Gene transfer between bacteria via a bacterial plasmid is a fascinating technique which allows these organisms to transfer genetic material horizontally, rather than being limited to passing it between generations. This is one of the reasons bacteria have been able to thrive for so long, because they can adapt to their environments extremely quickly. For example, if an antibiotic is introduced, bacteria with plasmids which help them resist that antibiotic can pass those plasmids on to other poasmids.
Genetic researchers take advantage of the plasmid as an ideal vector for carrying DNA for research purposes. They use a conjugating plasmid which is wjat to transfer genetic material, and insert plasmidz DNA of their choice into the plasmid so that it will be transferred.
Then, they introduce the bacterial plasmid to a cell culture, allowing the cells to become infected, so to speak, with the new genetic material, which will then bactsria reproduced when the cells divide.
Thanks to the widespread use of how to become a children and family social worker in genetic research, a number of labs are capable of generating plasmids for research by request.
Scientists can order a bacterial plasmid from one of these labs, bactetia the lab will insert the target DNA whatt package the bacterial plasmid for use. In plasmiids cases, researchers may prefer to prepare their own plasmids for research, for a variety of reasons bacterua from a desire to control the conditions of the experiment to concerns about the security of the DNA they are researching. Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer.
Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors. Please enter the following code:. Login: Forgot password?
Plasmids are relatively small, usually circular, DNA molecules. Most plasmids that have been found in lactic acid bacteria are cryptic, that is, their presence or absence has no apparent effect on growth, survival, or other observed properties of the bacterium. Plasmids are remarkably common in .
Plasmid , in microbiology, an extrachromosomal genetic element that occurs in many bacterial strains. Plasmids are circular deoxyribonucleic acid DNA molecules that replicate independently of the bacterial chromosome. They are not essential for the bacterium but may confer a selective advantage. One class of plasmids, colicinogenic or Col factors, determines the production of proteins called colicins, which have antibiotic activity and can kill other bacteria.
Another class of plasmids, R factors, confers upon bacteria resistance to antibiotics. Some Col factors and R factors can transfer themselves from one cell to another and thus are capable of spreading rapidly through a bacterial population. A plasmid that is attached to the cell membrane or integrated into the bacterial chromosome is called an episome q. Plasmids are extremely valuable tools in the fields of molecular biology and genetics, specifically in the area of genetic engineering q.
They play a critical role in such procedures as gene cloning, recombinant protein production e. In such procedures, a plasmid is cut at a specific site or sites using enzymes called restriction endonucleases. A foreign DNA element such as the gene for insulin is then spliced into the plasmid. The resulting circular structure, a recombinant DNA molecule, is then introduced into bacterial cells a process called transformation. The autonomous replication of the plasmid within the bacterial cells makes it possible to produce large numbers of copies of the recombinant DNA molecule for experimental manipulation or commercial purposes such as the production of large amounts of insulin.
Plasmids are well suited to genetic engineering in other ways. Their antibiotic resistance genes, for example, prove useful in identifying those bacterial cells that have taken up the recombinant DNA molecule in a high background of untransformed cells transformation frequencies are only about 1 out of every , cells. Videos Images. Additional Info. More About Contributors Article History.
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Learn More in these related Britannica articles:. Bacterial plasmids are circular DNA molecules; some carry genes for resistance to various agents in the environment that would be toxic to the bacteria e. Many fungi and some plants possess plasmids in their mitochondria; most of these are linear DNA molecules carrying….
Viral and plasmidnucleic acids pass from cell to cell where the DNA or RNA perform their replication and coding functions efficiently. Conjugative plasmids encode an extremely efficient mechanism that mediates their own transfer from a donor cell to a recipient cell. The process takes place in one direction since only the donor cells contain the conjugative plasmid.
In gram-negative bacteria, donor cells…. History at your fingertips. Sign up here to see what happened On This Day , every day in your inbox! Email address. By signing up, you agree to our Privacy Notice. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox.