However, it is not sexual reproduction, since no exchange of gamete occurs, and indeed no generation of a new organism: instead an existing organism is transformed. During classical E. coli conjugation the donor cell provides a conjugative or mobilizable genetic element that is most often a plasmid or transposon. Most conjugative plasmids have systems ensuring that the recipient cell does not already contain a similar element. The genetic information transferred is often beneficial to the recipient.
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Relaxase nomenclature is varied. In conjugative bacterial plasmids, Mob-class relaxases go by names such as TraI (in plasmid RP4), VirD2 (pTi), TrwC (R388), TraI (F-plasmid), MobB (CloDF13), or TrsK (pGO1).
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It is very common for the resistance genes or entire resistance cassettes to be re-arranged on the same plasmid or be moved to a different plasmid or chromosome by means of recombination systems. Examples of such systems include integrons and transposons. Most of the resistance plasmids are conjugative, meaning that they encode all the needed components for the transfer of the plasmid to other bacterium. Other smaller plasmids (usually < 10 kb in size) can be mobilized by a conjugative plasmid (usually > 30 kb) in order to be transferred.
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Conjugative hydrocyanation has been heavily used for steroid synthesis. Originally, it was used to prepare the steroidal D ring, but other approaches have also been employed.Nagata, W. ; Terasawa, T. ; Hirai, S. ; Takeda, K. Tetrahedron Lett., 1960, 17, 27.
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This theory was corroborated through computer modelling. Toxin-antitoxin systems can also be found on other mobile genetic elements such as conjugative transposons and temperate bacteriophages and could be implicated in the maintenance and competition of these elements.
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Triparental mating is a form of Bacterial conjugation where a conjugative plasmid present in one bacterial strain assists the transfer of a mobilizable plasmid present in a second bacterial strain into a third bacterial strain. Plasmids are introduced into bacteria for such purposes as transformation, cloning, or transposon mutagenesis. Triparental matings can help overcome some of the barriers to efficient plasmid mobilization. For instance, if the conjugative plasmid and the mobilizable plasmid are members of the same incompatibility group they do not need to stably coexist in the second bacterial strain for the mobilizable plasmid to be transferred.
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Relaxase may work alone or in a complex of over a dozen proteins known collectively as a relaxosome. In the F-plasmid system the relaxase enzyme is called TraI and the relaxosome consists of TraI, TraY, TraM and the integrated host factor IHF. The nicked strand, or T-strand, is then unwound from the unbroken strand and transferred to the recipient cell in a 5'-terminus to 3'-terminus direction. The remaining strand is replicated either independent of conjugative action (vegetative replication beginning at the oriV) or in concert with conjugation (conjugative replication similar to the rolling circle replication of lambda phage).
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Both pathogens rely on a conjugative virulence plasmid to cause disease. In case of R. fascians, this is a linear plasmid, whereas R. equi harbors a circular plasmid. Both pathogens are economically significant. R. fascians is a major pathogen of tobacco plants.
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The Ti and Ri plasmids are themselves conjugative. Ti and Ri transfer between bacteria uses an independent system (the tra, or transfer, operon) from that for inter-kingdom transfer (the vir, or virulence, operon). Such transfer creates virulent strains from previously avirulent Agrobacteria.
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Genes encoding restriction modification systems have been reported to move between prokaryotic genomes within mobile genetic elements such as plasmids, prophages, insertion sequences/transposons, integrative conjugative elements (ICEs), and integrons. Still, they are more frequently a chromosomal-encoded barrier to MGEs than an MGE-encoded tool for cell infection. Lateral gene transfer via a mobile genetic element, namely the Integrated Conjugative Element ICEBs1 has been reported for its role in the global DNA damage SOS response of the gram positive Bacillus subtilis. Furthermore it has been linked with the radiation and desiccation resistance of Bacillus pumilus SAFR-032 spores, isolated from spacecraft cleanroom facilities.
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1951, 572, 23. and other carbonyl derivatives also undergo conjugative hydrocyanation. When alkali metal cyanides are used, at least partial neutralization of the reaction medium is usually necessary to provide desired products. Neutralization can be accomplished through an acidic group on the substate itself (internal neutralization).
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In molecular biology, the histone-like nucleoid-structuring (H-NS) protein belongs to a family of bacterial proteins that play a role in the formation of nucleoid structure and affect gene expression under certain conditions. The protein has a homologue that is encoded by many large, conjugative plasmids.
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The H. defensa genome holds a 2,110,331-bp circular chromosome and a 59,034-bp conjugative plasmid. The chromosome carries a canonical origin of replication. It has notably more cell structure, DNA replication, recombination, and repair of genes than obligate endosymbionts, despite its limited biosynthetic abilities. The proteins present in H. defensa vary in length significantly.
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ZGRF1 contains a DUF2439 domain (domain of unknown function), zf-GRF domain, and AAA_11 and an AAA_12 domain (ATPases associated with diverse cellular activities). DUF domains are involved in telomere maintenance and meiotic segregation. AAA_11 and AAA_12 contain a P-loop motif which are involved in conjugative transfer proteins. Other helicase domains are also present in c4orf21 orthologs.
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The Actinobacterial 1 TMS Holin (A-1 Holin) Family (TC# 1.E.32) consists of proteins found in actinobacteria, their conjugative plasmids and their phage. They are usually between 90 and 140 amino acyl residues (aas) in length and exhibit 1 or sometimes even 2 transmembrane segments despite the families name (i.e., TC# 1.E.32.2.1).
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The V(D)J recombination system operates by a mechanism similar to that of some TEs. TEs can contain many types of genes, including those conferring antibiotic resistance and ability to transpose to conjugative plasmids. Some TEs also contain integrons, genetic elements that can capture and express genes from other sources. These contain integrase, which can integrate gene cassettes.
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Early transposon mutagenesis experiments relied on bacteriophages and conjugative bacterial plasmids for the insertion of sequences. These were very non-specific, and made it difficult to incorporate specific genes. A newer technique called shuttle mutagenesis uses specific cloned genes from the host species to incorporate genetic elements. Another effective approach is to deliver transposons through viral capsids.
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The distribution of products from conjugative hydrocyanation depends both on substrate structure and reaction conditions. Generally, however, acidic conditions favor 1,2-adducts, while basic conditions favor 1,4-adducts. As a result, under acidic conditions the cyanohydrins 2 and 4 are favored over the 1,4-adduct 3. Conditions of kinetic control also favor 1,2-adducts, while conditions of thermodynamic control favor the 1,4-adduct.
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Plasmids are common to be seen in Roseobacters. The size of plasmids range from 4.3 to 821.7 Kb. They can make up 20% of the genome content. Ecologically relevant genes can be found encoded on plasmids. Genome plasticity could be a reason to explain the diversity and adaptability of Roseobacters, which is supported by the high number of probably conjugative plasmids.
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Pathogenicity islands (PAIs), as termed in 1990, are a distinct class of genomic islands acquired by microorganisms through horizontal gene transfer. Pathogenicity islands are found in both animal and plant pathogens. Additionally, PAIs are found in both gram-positive and gram-negative bacteria. They are transferred through horizontal gene transfer events such as transfer by a plasmid, phage, or conjugative transposon.
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Conjugative as well as DNA release and uptake systems play an important role in horizontal gene transfer, which allows prokaryotes to adapt to their environment, such as, developing antibiotic resistance. Effector systems allow for the interaction between microbes and larger organisms. The effector systems are used as a toxin delivery method by many human pathogens such as, Helicobacter pylori (stomach ulcers), whooping cough, and Legionnaires' disease.
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The large growths on these roots are galls induced by Agrobacterium sp. Agrobacterium tumefaciens causes crown-gall disease in plants. The disease is characterised by a tumour-like growth or gall on the infected plant, often at the junction between the root and the shoot. Tumors are incited by the conjugative transfer of a DNA segment (T-DNA) from the bacterial tumour- inducing (Ti) plasmid.
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Hydrogen cyanide alone is not reactive enough to add to carbonyl groups; as a result, base catalysis is necessary. Conjugative hydrocyanation is limited by some side reactions and the strongly basic conditions typically employed. Product hydrolysis should be expected in reactions of alkali metal cyanides. Epimerization at the α-position of carbonyls, double bond isomerization, and α-acetoxy rearrangements have all been observed as side reactions under basic conditions.
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Conjugative pili allow for the transfer of DNA between bacteria, in the process of bacterial conjugation. They are sometimes called "sex pili", in analogy to sexual reproduction, because they allow for the exchange of genes via the formation of "mating pairs". Perhaps the most well-studied is the pilus of Escherichia coli, encoded by the fertility F sex factor. A pili is typically 6 to 7 nm in diameter.
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The conjugation machinery of some bacteria (and archaeal flagella) is capable of transporting both DNA and proteins. It was discovered in Agrobacterium tumefaciens, which uses this system to introduce the Ti plasmid and proteins into the host, which develops the crown gall (tumor). The VirB complex of Agrobacterium tumefaciens is the prototypic system. The nitrogen fixing Rhizobia are an interesting case, wherein conjugative elements naturally engage in inter-kingdom conjugation.
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Multiple genetic elements of human-affecting pathogens contribute to the transfer of virulence factors: plasmids, pathogenicity island, prophages, bacteriophages, transposons, and integrative and conjugative elements. Pathogenicity islands and their detection are the focus of several bioinformatics efforts involved in pathogenomics. It is a common belief that "environmental bacterial strains" lack the capacity to harm or do damage to humans. However, recent studies show that bacteria from aquatic environments have acquired pathogenic strains through evolution.
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In short, Type IV secretion system (T4SS), is the general mechanism by which bacterial cells secrete or take up macromolecules. Their precise mechanism remains unknown. T4SS is encoded on Gram-negative conjugative elements in bacteria.T4SS are cell envelope-spanning complexes or in other words 11–13 core proteins that form a channel through which DNA and proteins can travel from the cytoplasm of the donor cell to the cytoplasm of the recipient cell.
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Conjugative replication may require a second nick before successful transfer can occur. A recent report claims to have inhibited conjugation with chemicals that mimic an intermediate step of this second nicking event. 1.The insertion sequences (yellow) on both the F factor plasmid and the chromosome have similar sequences, allowing the F factor to insert itself into the genome of the cell. This is called homologous recombination and creates an Hfr (high frequency of recombination) cell. 2.
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The infinitive has only one form (nešti). These forms, except the infinitive and indirect mood, are conjugative, having two singular, two plural persons and the third person form common both for plural and singular. In the passive voice, the form number is not as rich as in the active voice. There are two types of passive voice in Lithuanian: present participle (type I) and past participle (type II) (in the examples below types I and II are separated with a slash).
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Another example of effects mediated by the AHR via non-canonical pathways is suppression of acute-phase proteins (6.) which does not involve DNA binding. (simplified and modified from Lindén et al.) The AH receptor is relevant in toxicology for two very different reasons. First, it induces several enzymes important in the metabolism of foreign substances, so called xenobiotics. These include both oxidative phase I enzymes and conjugative phase II enzymes, e.g. CYP1A2, CYP1B1, CYP2S1, CYP2A5, ALDH3, GSTA1, UGT1A1, UGT1A6, UGT1A7 and NQO1.
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Integrons were initially discovered on conjugative plasmids through their role in antibiotic resistance. Indeed, these mobile integrons, as they are now known, can carry a variety of cassettes containing genes that are almost exclusively related to antibiotic resistance. Further studies have come to the conclusion that integrons are chromosomal elements, and that their mobilisation onto plasmids has been fostered by transposons and selected by the intensive use of antibiotics. The function of the majority of cassettes found in chromosomal integrons remains unknown.
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Types are genetically distinct and use separate sets of proteins, however, proteins between the sets have strong homologies to each other, which leads them to function similarly. Type IV secretion systems are also classified by function into three main types. Conjugative systems: used for DNA transfer via cell to cell contact (a process called conjugation); DNA release and uptake systems: used to exchange DNA with the extracellular environment (a process called transformation); and effector systems: used to transfer proteins to target cells.
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The Micalizio route (2011) achieved the end product in 9 steps from a commercially available acetyl-pyridine. Notable reactions include a [2,3]-Still-Wittig rearrangement and a conformationally-controlled intramolecular Mannich cyclization. The Weinreb group (2014) used a conjugative addition of an indole precursor to an oxime-substituted nitrosoalkene to generate the tetracyclic skeleton of conolidine in 4 steps. Takayama and colleagues (2016) synthesized conolidine and apparicine through a gold(I)-catalyzed exo-dig synthesis of a racemic piperidinyl aldehyde.
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The Huambisa language has a wide vocabulary that has been extensively documented in the last century. The Huambisan lexicon is said to be similar to that of the Aguaruna language as well. The breadth of the Huambisa vocabulary can be mainly attributed to speakers' specification of context in their word choice. For example, the English verb "to open" applies to a wide range of objects which it can be acting upon, while the Huambisa lexicon contains at least 5 different words which mean "to open," all of which then have at least 3 conjugative forms.
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Prior to discussing the conjugable words, a brief note about stem forms. Conjugative suffixes and auxiliary verbs are attached to the stem forms of the affixee. In modern Japanese there are the following six stem forms. Note that this order follows from the -a, -i, -u, -e, -o endings that these forms have in 五段 (5-row) verbs (according to the あ、い、う、え、お collation order of Japanese), where terminal and attributive forms are the same for verbs (hence only 5 surface forms), but differ for nominals, notably na-nominals.
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R-M systems are major players in the co-evolutionary interaction between mobile genetic elements (MGEs) and their hosts. Genes encoding R-M systems have been reported to move between prokaryotic genomes within MGEs such as plasmids, prophages, insertion sequences/transposons, integrative conjugative elements (ICEs) and integrons. However, it was recently found that there are relatively few R-M systems in plasmids, some in prophages, and practically none in phages. On the other hand, all these MGEs encode a large number of solitary R-M genes, notably MTases.
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Ros binds to a region of DNA that overlaps with the binding site of the VirG regulator, and therefore competes with VirG to control their expression levels. Functionally, VirC1 and VirC2 promote the assembly of a relaxosome complex during the conjugative transfer of T-DNA from the bacteria to the host plant cell. This is an energy-dependent process mediated via their NTPase activity, and occurs as they bind to a region of DNA known as overdrive. As a result, they act to increase the amount of T-DNA strands produced.
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An Hfr cell can transfer a portion of the bacterial genome. Despite being integrated into the chromosomal DNA of the bacteria, the F factor of Hfr cells can still initiate conjugative transfer, without being excised from the bacterial chromosome first. Due to the F factor's inherent tendency to transfer itself during conjugation, the rest of the bacterial genome is dragged along with it. Therefore, unlike a normal F+ cell, Hfr strains will attempt to transfer their entire DNA through the mating bridge, in a fashion similar to the normal conjugation.
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The repeated DNA sequence includes short repetitive sequences, transposable elements (including insertion sequence elements, miniature inverted-repeat transposable elements, a Group II intron), and a greatly amplified integrative and conjugative element (ICE) called the rickettsial amplified genetic element (RAGE). RAGE is also found in other rickettsial bacteria. In O. tsutsugamushi, however, RAGE contains a number of genes including tra genes typical of type IV secretion systems and gene for ankyrin repeat–containing protein. Ankyrin repeat–containing proteins are secreted through a type I secretion system into the host cell.
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In bacteria, many type 3 secretion systems and type 4 secretion systems are located on regions of DNA called genomic islands. These "islands" are characterised by their large size(>10 Kb), their frequent association with tRNA-encoding genes and a different G+C content compared with the rest of the genome. Many genomic islands are flanked by repeat structures and carry fragments of other mobile elements such as phages and plasmids. Some genomic islands, including those adjacent to integrative and conjugative elements (ICE), can excise themselves spontaneously from the chromosome and can be transferred to other suitable recipients.
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The fertility factor (first named F by one of its discoverers Esther Lederberg; also called the sex factor in E. coli or the F sex factor; also called F-plasmid) allows genes to be transferred from one bacterium carrying the factor to another bacterium lacking the factor by conjugation. The F factor was the first plasmid to be discovered. Unlike other plasmids, F factor is constitutive for transfer proteins due to a mutation in the gene finO. The F plasmid belongs to a class of conjugative plasmids that control sexual functions of bacteria with a fertility inhibition (Fin) system.
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When an F+ cell conjugates/mates with an F− cell, the result is two F+ cells, both capable of transmitting the plasmid to other F− cells by conjugation. A pilus on the F+ cell interacts with the recipient cell allowing formation of a mating junction, the DNA is nicked on one strand, unwound and transferred to the recipient. The F-plasmid belongs to a class of conjugative plasmids that control sexual functions of bacteria with a fertility inhibition (Fin) system. In this system, a trans-acting factor, FinO, and antisense RNAs, FinP, combine to repress the expression of the activator gene TraJ.
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Glucuronosyltransferases are responsible for the process of glucuronidation, a major part of phase II metabolism. Arguably the most important of the Phase II (conjugative) enzymes, UGTs have been the subject of increasing scientific inquiry since the mid-to-late 1990s. The reaction catalyzed by the UGT enzyme involves the addition of a glucuronic acid moiety to xenobiotics and is the most important pathway for the human body's elimination of the most frequently prescribed drugs. It is also the major pathway for foreign chemical (dietary, environmental, pharmaceutical) removal for most drugs, dietary substances, toxins and endogenous substances.
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Due to the wide variety of type IV secretion systems in both origin and function, it is difficult to state much mechanistically about the group as a whole. In general, after DNA is packaged in a conjugative system it is recruited by ATPase analogues to the VirD4 coupling protein, then translocated through the pilus. In A. tumefaciens specifically, the DNA passes through a characterized chain of enzymes before reaching the pilus. The DNA is recruited by VirD4, then VirB11, then to the intermembrane proteins (VirB6, and VirB8), moved to VirB9, and finally sent to the pilus (VirB2).
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Analysis of the extra- chromosomal genome showed that there was a group of putative plasmids encoding several groups of Type IV pili genes; these of which showed high homology with that of gammaproteobacteria conjugative transfer genes. Further phylogenetic analysis using a basic matrix revealed that the genus Arsenophonus forms a monophyletic clade. In terms of bacterial metabolism, A. nasoniae is only present in a fraction of wasp hosts therefore the bacterium is unlikely to significantly contribute to the nutrition of the host insect. A. nasoniae was able to grow on cell-free media but required additional nutritional supplementation.
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These experiments led to the conclusion that competence, with uptake of DNA, is specifically induced by DNA-damaging conditions, and that transformation functions as a process for recombinational repair of DNA damage. While the natural competent state is common within laboratory B. subtilis and field isolates, some industrially relevant strains, e.g. B. subtilis (natto), are reluctant to DNA uptake due to the presence of restriction modification systems that degrade exogenous DNA. B. subtilis (natto) mutants, which are defective in a type I restriction modification system endonuclease, are able to act as recipients of conjugative plasmids in mating experiments, paving the way for further genetic engineering of this particular B. subtilis strain.
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T-DNA contains two types of genes: the oncogenic genes, encoding for enzymes involved in the synthesis of auxins and cytokinins and responsible for tumor formation; and the genes encoding for the synthesis of opines. These compounds, produced by condensation between amino acids and sugars, are synthesized and excreted by the crown gall cells and consumed by A. tumefaciens as carbon and nitrogen sources. Outside the T-DNA, are located the genes for the opine catabolism, the genes involved in the process of T-DNA transfer from the bacterium to the plant cell and the genes involved in bacterium-bacterium plasmid conjugative transfer. (Hooykaas and Schilperoort, 1992; Zupan and Zambrysky, 1995).
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333x333px Bacteria can alter their genetic inheritance through two main ways, either by mutating their genetic material or acquiring a new one from other bacteria. The latter being the most important for causing antibiotic-resistant bacteria strains in animals and humans. One of the methods bacteria can obtain new genes is through a process called conjugation which deals with transferring genes using plasmids. These conjugative plasmids carry a number of genes that can be assembled and rearranged, which could then enable bacteria to exchange beneficial genes among themselves ensuring their survival against antibiotics and rendering them ineffective to treat dangerous diseases in humans, resulting into multi-drug resistant organisms.
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During conjugation, a pilus emerging from the donor bacterium ensnares the recipient bacterium, draws it in close, and eventually triggers the formation of a mating bridge, which establishes direct contact and the formation of a controlled pore that allows transfer of DNA from the donor to the recipient. Typically, the DNA transferred consists of the genes required to make and transfer pili (often encoded on a plasmid), and so is a kind of selfish DNA; however, other pieces of DNA are often co-transferred and this can result in dissemination of genetic traits throughout a bacterial population, such as antibiotic resistance. Not all bacteria can make conjugative pili, but conjugation can occur between bacteria of different species.
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Though there is some debate on the exact mechanism of conjugation it seems that the pili are not the structures through which DNA exchange occurs. This has been shown in experiments where the pilus are allowed to make contact, but then are denatured with SDS and yet DNA transformation still proceeds. Several proteins coded for in the tra or trb locus seem to open a channel between the bacteria and it is thought that the traD enzyme, located at the base of the pilus, initiates membrane fusion. When conjugation is initiated by a signal the relaxase enzyme creates a nick in one of the strands of the conjugative plasmid at the oriT.
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Plasmids are transmitted from one bacterium to another (even of another species) mostly through conjugation. This host-to-host transfer of genetic material is one mechanism of horizontal gene transfer, and plasmids are considered part of the mobilome. Unlike viruses, which encase their genetic material in a protective protein coat called a capsid, plasmids are "naked" DNA and do not encode genes necessary to encase the genetic material for transfer to a new host; however, some classes of plasmids encode the conjugative "sex" pilus necessary for their own transfer. The size of the plasmid varies from 1 to over 200 kbp, and the number of identical plasmids in a single cell can range anywhere from one to thousands under some circumstances.
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In a typical conjugation, the recipient cell also becomes F+ after conjugation as it receives an entire copy of the F factor plasmid; but this is not the case in conjugation mediated by Hfr cells. Due to the large size of bacterial chromosome, it is very rare for the entire chromosome to be transferred into the F − cell as time required is simply too long for the cells to maintain their physical contact. Therefore, as the conjugative transfer is not complete (the circular nature of plasmid and bacterial chromosome requires complete transfer for the F factor to be transferred as it may be cut in the middle), the recipient F− cells do not receive the complete F factor sequence, and do not become F + due to its inability to form a sex pilus.
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The T-DNA fragment is flanked by 25-bp direct repeats, which act as a cis element signal for the transfer apparatus. The process of T-DNA transfer is mediated by the cooperative action of proteins encoded by genes determined in the Ti plasmid virulence region (vir genes) and in the bacterial chromosome. The Ti plasmid also contains the genes for opine catabolism produced by the crown gall cells, and regions for conjugative transfer and for its own integrity and stability. The 30 kb virulence (vir) region is a regulon organized in six operons that are essential for the T-DNA transfer (virA, virB, virD, and virG) or for the increasing of transfer efficiency (virC and virE) (Hooykaas and Schilperoort, 1992; Zupan and Zambryski, 1995, Jeon et al.
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Because such strains transfer chromosomal genes very efficiently they are called Hfr (high frequency of recombination). The E. coli genome was originally mapped by interrupted mating experiments in which various Hfr cells in the process of conjugation were sheared from recipients after less than 100 minutes (initially using a Waring blender). The genes that were transferred were then investigated. Since integration of the F-plasmid into the E. coli chromosome is a rare spontaneous occurrence, and since the numerous genes promoting DNA transfer are in the plasmid genome rather than in the bacterial genome, it has been argued that conjugative bacterial gene transfer, as it occurs in the E. coli Hfr system, is not an evolutionary adaptation of the bacterial host, nor is it likely ancestral to eukaryotic sex.
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The conjugation of 1,3-butadiene was first evaluated by Kistiakowsky, a conjugative contribution of 3.5 kcal/mol was found based on the energetic comparison of hydrogenation between conjugated species and unconjugated analogues. Rogers who used the method first applied by Kistiakowsky, reported that the conjugation stabilization of 1,3-butadiyne was zero, as the difference of ΔhydH between first and second hydrogenation was zero. The heats of hydrogenation (ΔhydH) were obtained by computational G3(MP2) quantum chemistry method. 540px Another group led by Houk suggested the methods employed by Rogers and Kistiakowsky was inappropriate, because that comparisons of heats of hydrogenation evaluate not only conjugation effects but also other structural and electronic differences. They obtained -70.6 kcal/mol and -70.4 kcal/mol for the first and second hydrogenation respectively by ab initio calculation, which confirmed Rogers’ data.
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