A report on Transformation (genetics)

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Schematic of bacterial transformation – for which artificial competence must first be induced.

Genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings through the cell membrane.

- Transformation (genetics)
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Illustration of a bacterium showing chromosomal DNA and plasmids (Not to scale)

Plasmid

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Small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently.

Small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently.

Illustration of a bacterium showing chromosomal DNA and plasmids (Not to scale)
There are two types of plasmid integration into a host bacteria: Non-integrating plasmids replicate as with the top instance, whereas episomes, the lower example, can integrate into the host chromosome.
Overview of bacterial conjugation
Electron micrograph of a DNA fiber bundle, presumably of a single bacterial chromosome loop
Electron micrograph of a bacterial DNA plasmid (chromosome fragment)
A schematic representation of the pBR322 plasmid, one of the first plasmids to be used widely as a cloning vector. Shown on the plasmid diagram are the genes encoded (amp and tet for ampicillin and tetracycline resistance respectively), its origin of replication (ori), and various restriction sites (indicated in blue).

In the laboratory, plasmids may be introduced into a cell via transformation.

Schematic drawing of bacterial conjugation.

Bacterial conjugation

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Transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells.

Transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells.

Schematic drawing of bacterial conjugation.
Agrobacterium tumefaciens gall at the root of Carya illinoensis.

It is a mechanism of horizontal gene transfer as are transformation and transduction although these two other mechanisms do not involve cell-to-cell contact.

Tree of life showing vertical and horizontal gene transfers

Horizontal gene transfer

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Movement of genetic material between unicellular and/or multicellular organisms other than by the ("vertical") transmission of DNA from parent to offspring (reproduction).

Movement of genetic material between unicellular and/or multicellular organisms other than by the ("vertical") transmission of DNA from parent to offspring (reproduction).

Tree of life showing vertical and horizontal gene transfers
A speciation event produces orthologs of a gene in the two daughter species. A horizontal gene transfer event from one species to another adds a xenolog of the gene to the receiving genome.
1: Donor bacteria 2: Bacteria who will receive the gene   3: The red portion represents the gene that will be transferred.   Transformation in bacteria happens in a certain environment.
1: Donor bacteria cell (F+ cell) 2: Bacteria that receives the plasmid (F- cell)   3: Plasmid that will be moved to the other bacteria   4: Pilus.   Conjugation in bacteria using a sex pilus; then the bacteria that received the plasmid can go give it to other bacteria as well.
Before it is transformed, a bacterium is susceptible to antibiotics. A plasmid can be inserted when the bacteria is under stress, and be incorporated into the bacterial DNA creating antibiotic resistance. When the plasmids are prepared they are inserted into the bacterial cell by either making pores in the plasma membrane with temperature extremes and chemical treatments, or making it semi permeable through the process of electrophoresis, in which electric currents create the holes in the membrane. After conditions return to normal the holes in the membrane close and the plasmids are trapped inside the bacteria where they become part of the genetic material and their genes are expressed by the bacteria.

Genes responsible for antibiotic resistance in one species of bacteria can be transferred to another species of bacteria through various mechanisms of HGT such as transformation, transduction and conjugation, subsequently arming the antibiotic resistant genes' recipient against antibiotics.

Microscopic image of gram-negative Pseudomonas aeruginosa bacteria (pink-red rods)

Gram-negative bacteria

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Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation.

Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation.

Microscopic image of gram-negative Pseudomonas aeruginosa bacteria (pink-red rods)
Gram-negative cell wall structure
Gram-positive and -negative bacteria are differentiated chiefly by their cell wall structure

Transformation is one of three processes for horizontal gene transfer, in which exogenous genetic material passes from bacterium to another, the other two being conjugation (transfer of genetic material between two bacterial cells in direct contact) and transduction (injection of foreign DNA by a bacteriophage virus into the host bacterium).

Natural competence

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[[File:Natural Competence Drawing.svg|thumb|Natural competence.

[[File:Natural Competence Drawing.svg|thumb|Natural competence.

In microbiology, genetics, cell biology, and molecular biology, competence is the ability of a cell to alter its genetics by taking up extracellular ("naked") DNA from its environment in the process called transformation.

Streptococcus pneumoniae

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Gram-positive, spherical bacteria, alpha-hemolytic or beta-hemolytic (under anaerobic conditions), aerotolerant anaerobic member of the genus Streptococcus.

Gram-positive, spherical bacteria, alpha-hemolytic or beta-hemolytic (under anaerobic conditions), aerotolerant anaerobic member of the genus Streptococcus.

Optochin sensitivity in a culture of Streptococcus pneumoniae (white disk)

In 1928, Frederick Griffith demonstrated transformation of life turning harmless pneumococcus into a lethal form by co-inoculating the live pneumococci into a mouse along with heat-killed virulent pneumococci.

Structural model at atomic resolution of bacteriophage T4

Bacteriophage

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Virus that infects and replicates within bacteria and archaea.

Virus that infects and replicates within bacteria and archaea.

Structural model at atomic resolution of bacteriophage T4
The structure of a typical myovirus bacteriophage
Anatomy and infection cycle of phage T4.
Bacteriophage P22, a member of the Podoviridae by morphology due to its short, non-contractile tail
Bacteriophage T2, a member of the Myoviridae due to its contractile tail
Félix d'Herelle
George Eliava
Diagram of the DNA injection process
In this electron micrograph of bacteriophages attached to a bacterial cell, the viruses are the size and shape of coliphage T1
Schematic view of the 44 kb T7 phage genome. Each box is a gene. Numbers indicate genes (or rather open reading frames).

Bacteriophages are thought to contribute extensively to horizontal gene transfer in natural environments, principally via transduction, but also via transformation.

Griffith's experiment discovering the "transforming principle" in pneumococcus bacteria.

Griffith's experiment

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Griffith's experiment discovering the "transforming principle" in pneumococcus bacteria.

Griffith's experiment, reported in 1928 by Frederick Griffith, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation.

Rat nerve cells express red and green fluorescent proteins after viral transduction with two artificial adeno-associated viruses.

Transduction (genetics)

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Process by which foreign DNA is introduced into a cell by a virus or viral vector.

Process by which foreign DNA is introduced into a cell by a virus or viral vector.

Rat nerve cells express red and green fluorescent proteins after viral transduction with two artificial adeno-associated viruses.

Transduction does not require physical contact between the cell donating the DNA and the cell receiving the DNA (which occurs in conjugation), and it is DNase resistant (transformation is susceptible to DNase).

Rod-shaped gram-positive Bacillus anthracis bacteria in a cerebrospinal fluid sample stand out from round white blood cells, which also accept the crystal violet stain.

Gram-positive bacteria

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Traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall.

Traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall.

Rod-shaped gram-positive Bacillus anthracis bacteria in a cerebrospinal fluid sample stand out from round white blood cells, which also accept the crystal violet stain.
Violet-stained gram-positive cocci and pink-stained gram-negative bacilli
Gram-positive and gram-negative cell wall structure
Structure of gram-positive cell wall
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The structure of peptidoglycan, composed of N-acetylglucosamine and N-acetylmuramic acid
Colonies of a gram-positive pathogen of the oral cavity, Actinomyces sp.

Transformation is one of three processes for horizontal gene transfer, in which exogenous genetic material passes from a donor bacterium to a recipient bacterium, the other two processes being conjugation (transfer of genetic material between two bacterial cells in direct contact) and transduction (injection of donor bacterial DNA by a bacteriophage virus into a recipient host bacterium).