Bacterial Conjugation

bacterial mating is mavin of the canonical methods by which simple organisms, such as the single-celled bacterium, reproduce. It is a very basic form of copulation that often involves a transfer of DNA merely no recombination following the said transfer. It occurs following the get into together of ii bacteria, a donor and a recipient. It is sexual activity in the bacterial world. The work of conglutination is made possible by the presence of certain plasmids in the donor bacteria that possess genes for m uniformg the proteins involved in docking and transfer. (The capital of South Carolina encyclopedia, Sixth Edition 2004) These plasmids argon the ones carried forward from one bacteria to the other(a) bacteria. A plasmid is an extra-chromosomal piece of bacterial DNA (deoxyribonucleic acid). Plasmids are maintained inside the bacterial cell, replicating fast enough until they are passed on to bacterial progeny as the bacteria divide. Plasmids are just standardized chro mosomes. They are circular and essentially double-stranded DNA.The distinct characteristics that set a persona plasmids from chromosomes are in their size and the genes that they carry. Plasmids are much smaller in size than chromosomes. Plasmids carry only genes that are essential. Bacteria are an interesting root word of organism. In order to better comprehend how bacteria multiplies, and replicates its genes, there is a need to understand its structure. Bacteria are microscopic unicellular procaryotic organisms characterised by the lack of a membrane-bound organelles. (The Columbia encyclopedia, Sixth Edition 2004) Bacteria are remarkably adaptable to diverse environmental conditions they are raise in the bodies of all living organisms and on all parts of the landed estate in land terrain and ocean depths, in arctic ice and glaciers, in hot springs, and even in the stratosphere. Most bacteria are of one of three typical shapes rod-shaped (bacillus), round (coccus), and spir al (spirillum). The cytoplasm and germ plasm membrane of most bacterial cells are surrounded by a cell wall.In bacteria, the familial satisfying is organized in a never-ending strand of DNA. This circle of DNA is localized in an area called the nucleoid, exclusively there is no membrane surrounding a defined nucleus. In addition to the nucleoid, the bacterial cell may include one or more plasmids. Some bacteria are capable of specialized attribute of contagious recombination which involves the transfer of nucleic acid by individual polish off, that is, the butt against of spousal relationship. Recombination involves a process of shuffling genes by which new combinations can be generated. (The Columbia encyclopedia, Sixth Edition 2004) Genetic recombination in bacteria may be mediated by transformation, transduction, or conjugation. In these methods, genetic transfers occur unidirectionally from donor to recipient bacteria and only a fraction of the genetic material of a do nor cell is transferred to a recipient, which, on the other hand, contributes its cytoplasm as well as its entire genome. In conjugation, the genetic office of the donor (male) is in neck and is genetically and physiologically determined.In so doing, the system of conjugation is well adapted to providing information about the temperament and organization of the bacterial chromosome as a whole as well as to the acquire of nuclear-cytoplasmic interactions. (Burdette et. al. 1963) In E. coli bacteria, the contagious sex compute responsible for the donor state, and thence for fertility, was called F, donor cells being F+ and recipient cell F-. From population of F+ cells, stores of a new type of donor called Hfr (for high frequency of recombination) were now and then isolated.Both F+ and Hfr donors share the following characteristics that distinguish with F- recipients they possess similar come forward properties that enable them to pair specialally and to mate with F- cells w ith comparable efficiency they declare the actual or potential ability to transfer genetic determinants to recipients, although the nature of the determinants so transferred by the two types of donor may be of quite an several(predicate) kinds all(prenominal) type of donor has the potentiality to mutate to the other or to the F- type and both types are under the control of a specific genetic structure, the sex accompanimentor F.F functions as a genetic particle insofar as it is stably inheritable by progeny, is transmissible in crosses, and is the determinant of those properties that characterize donor cells. (Burdette et. al. 1963) The facts recounted above and the interpretations they meet engendered may now be brought together to form a unified moving picture of the mating system in E. coli. The sexual differentiation of E. coli into males and females is genetically controlled by the presence or absence of a sex factor, F, that has the properties of an episome and is more akin in its behavior to temperate bacteriophage than to a normal genetic determinant.The propensities of male cells, in turn, are governed by the state in which the sex factor exists in them. F+ male cells, which harbor the sex factor in its autonomous state, preserve a continuous linkage grouping and, on conjugation, transfer only their sex factor and other extrachromosomal elements to females. They have the potentiality, however, to generate a spectrum of Hfr male types, each characterized by a linear, movable chromosome the extremities of which are defined by the integration of the sex factor at one of a variety of chromosomal sites only the proximal part of the linear chromosome is transferred with high efficiency.Such modified sex factors serve as cost-effective vehicles for the transport to female cells of their incorporated segments of male chromosome, with the result that stable, partial diploids for heterogeneous regions of the chromosome can readily be synthesized. (Bu rdette et. al. 1963) Formation of the zygote extends from the initial opposition surrounded by an Hfr and an F- cell to the completion of chromosomal transfer and comprises the stages of collision, effective contact formation, and chromosomal transfer.In interrupted mating, a number of different Hfr markers are selected, each is found to enter the zygotes at a different metre that is specific for each marker under standard conditions. The times of entry of the unhomogeneous markers correspond to their order of arrangement on the chromosome and are proportional to their distances from O where O indicates the extremity (leading locus) which first penetrates the recipient cells during conjugation. The crotchetyity of conjugation resides in the mechanism by which genetic transfer is accomplished.This is expressed by the fact that, when different selections are made, the different genetic characters of a given Hfr strain are transmitted to recombinants with different frequencies dep ending on their distances from O. The system thus lends itself to an first and convenient method of mapping, in terms of time of transfer. Moreover, mapping is greatly facilitated by the availability of a number of different Hfr strains that transfer different parts of the chromosome at high frequency. In all systems other than conjugation in E.coli, the only practical musical mode of measuring the distance between genetic loci is by comparing the frequency with which recombination occurs between them. In conjugation two additional methods of measurement are available, in terms of transfer time and of the decay of P32 atoms, both of which are absolute and independent of the recombination process and so provide the means of interpreting recombinational events in physical terms. Therefore, bacterial conjugations significance in gene mapping exists in its capability to determine the precise view of genes on the genome. Studies concerning a peculiar bacterial strain, E.coli Hfr, whic h engaged in conjugation with surprising frequency, paved the way for its use in 21st century genetics. By sundering conjugal bugs at various times during mating, geneticists Francois Jacob and Elie Wollman were able to determine that the male transferred a complete copy of its genome like one long piece of spaghetti. The implications of the notorious copulation interruptus experiment and the resulting spaghetti hypothesis were clear by carefully monitoring the time at which each trait was transferred, the two researchers could determine the precise positioning of genes on the genome.In this way they plotted the first crude genomic map of a bacterium. (Hirsch 1999, p. 145) References Burdette, WJ 1963, Methodology in Basic Genetics, Holden-Day, San Francisco. Hirsch, AE (1999, Spring). Of Flies, Mice and Men, American Scholar, p. 145. Johnson, AD (2002, Spring). supporting with Microbes, The Wilson Quarterly, pp. 42+. Rheinberger, HJ (ed. ) & Gaudilliere, JP 2004, Classical Genet ic Research and Its Legacy The Mapping Cultures of Twentieth-Century Genetics, Routledge, fresh York.