The mobilome is the entire set of

mobile genetic elements Mobile genetic elements (MGEs), sometimes called selfish genetic elements, are a type of genetic material that can move around within a genome, or that can be transferred from one species or replicon to another. MGEs are found in all organisms. In ...

in a

genome 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 genes, other functional regions of the genome such as ...

. Mobilomes are found in

eukaryotes The eukaryotes ( ) constitute the domain of Eukaryota or Eukarya, organisms whose cells have a membrane-bound nucleus. All animals, plants, fungi, seaweeds, and many unicellular organisms are eukaryotes. They constitute a major group of ...

prokaryotes A prokaryote (; less commonly spelled procaryote) is a single-celled organism whose cell lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Ancient Greek (), meaning 'before', and (), meaning 'nut' ...

, and

viruses 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. Viruses are found in almo ...

. The compositions of mobilomes differ among lineages of life, with transposable elements being the major mobile elements in eukaryotes, and

plasmids 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 and ...

and prophages being the major types in prokaryotes. Virophages contribute to the viral mobilome.

Mobilome in eukaryotes

Transposable element A transposable element (TE), also transposon, or jumping gene, is a type of mobile genetic element, a nucleic acid sequence in DNA that can change its position within a genome. The discovery of mobile genetic elements earned Barbara McClinto ...

s are elements that can move about or propagate within the genome, and are the major constituents of the

eukaryotic The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

mobilome. Transposable elements can be regarded as genetic

parasites Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...

because they exploit the host cell's transcription and

translation Translation is the communication of the semantics, 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 English la ...

mechanisms to extract and insert themselves in different parts of the genome, regardless of the

phenotypic In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...

effect on the host. Eukaryotic transposable elements were first discovered in

maize Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...

(''Zea mays'') in which kernels showed a dotted color pattern.

Barbara McClintock Barbara McClintock (June 16, 1902 – September 2, 1992) was an American scientist and cytogenetics, cytogeneticist who was awarded the 1983 Nobel Prize in Physiology or Medicine. McClintock received her PhD in botany from Cornell University ...

described the maize Ac/Ds system in which the Ac locus promotes the excision of the Ds locus from the genome, and excised Ds elements can mutate

genes In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

responsible for

pigment A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

production by inserting into their coding regions. Other examples of transposable elements include:

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom (biology), kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are est ...

(''Saccharomyces cerevisiae'') Ty elements, a

retrotransposon Retrotransposons (also called Class I transposable elements) are mobile elements which move in the host genome by converting their transcribed RNA into DNA through reverse transcription. Thus, they differ from Class II transposable elements, or ...

which encodes a

reverse transcriptase A reverse transcriptase (RT) is an enzyme used to convert RNA genome to DNA, a process termed reverse transcription. Reverse transcriptases are used by viruses such as HIV and hepatitis B to replicate their genomes, by retrotransposon mobi ...

to convert its mRNA transcript into DNA which can then insert into other parts of the genome; and fruit fly (''Drosophila melanogaster'') P-elements, which randomly inserts into the genome to cause mutations in germ line cells, but not in somatic cells.

Mobilome in prokaryotes

Plasmids were discovered in the 1940s as genetic materials outside of bacterial

chromosomes A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most importa ...

. Prophages are genomes of

bacteriophage A bacteriophage (), also known informally as a phage (), is a virus that infects and replicates within bacteria. The term is derived . Bacteriophages are composed of proteins that Capsid, encapsulate a DNA or RNA genome, and may have structu ...

s (a type of virus) that are inserted into bacterial chromosomes; prophages can then be spread to other bacteria through the lytic cycle and lysogenic cycle of

viral replication Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome ...

. While transposable elements are also found in prokaryotic genomes, the most common mobile genetic elements in the prokaryotic genome are

and prophages. Plasmids and prophages can move between genomes through

bacterial conjugation Bacterial conjugation is the transfer of genetic material between Bacteria, bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells. This takes place through a pilus. It is a parasexual cycle, parasexual mode ...

, allowing

horizontal gene transfer Horizontal gene transfer (HGT) or lateral gene transfer (LGT) is the movement of genetic material between organisms other than by the ("vertical") transmission of DNA from parent to offspring (reproduction). HGT is an important factor in the e ...

. Plasmids often carry genes that are responsible for bacterial

antibiotic resistance Antimicrobial resistance (AMR or AR) occurs when microbes evolve mechanisms that protect them from antimicrobials, which are drugs used to treat infections. This resistance affects all classes of microbes, including bacteria (antibiotic resis ...

; as these plasmids replicate and pass from one genome to another, the whole bacterial

population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

can quickly adapt to the

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

. Prophages can loop out of bacterial chromosomes to produce bacteriophages that go on to infect other bacteria with the prophages; this allows prophages to propagate quickly among the bacterial population, to the harm of the bacterial host.

Mobilome in viruses

Discovered in 2008 in a strain of ''Acanthamoeba castellanii mimivirus'', virophages are an element of the virus mobilome. Virophages are viruses that replicate only when host cells are co-infected with helper viruses. Following co-infection, helper viruses exploit the host cell's transcription/translation machinery to produce their own machinery; virophages replicate through the machinery of either the host cell or the viruses. The replication of virophages can negatively impact the replication of helper viruses.

Sputnik Sputnik 1 (, , ''Satellite 1''), sometimes referred to as simply Sputnik, was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space progra ...

and

mavirus ''Mavirus'' is a genus of double stranded DNA virus that can infect the marine phagotrophic flagellate '' Cafeteria roenbergensis'', but only in the presence of the giant '' CroV'' virus (''Cafeteria roenbergensis''). The genus contains only ...

are examples of virophages.

References

{{Self-replicating organic structures Genetics