Categories of Plasmid

1. Fertility Plasmid

Fertility plasmids, also called F-plasmids, contains transfer genes that permit qualities to be transferred starting from one bacteria then into the next, through conjugation. Bacteria that have the F-plasmid are known as F positive (F+), and bacteria without F- plasmid are F negative (F–). At the point when a F+ bacterium conjugates with a F–bacterium, two F+ bacterium result.

While the cells that possess the F plasmids are alluded to as donors, those that do not have this factor are the beneficiaries or recipients.

F plasmid assumes a significant job in proliferation given that they contain qualities that code for the creation of sex pilus and enzymes that are required for conjugation. F plasmid likewise contains qualities that are engaged with their own exchange. In this manner, during conjugation, they improve their transfer starting with one cell then onto the next.

During conjugation, the donor cell of bacteria with sex pili (1-3 sex pili) ties to a particular protein on the outer membrane layer of the recipient cell for starting the mating procedure. The pili then withdraw in this way permitting the two cells to tie together. This is then trailed by the transfer of DNA from the donor to the recipient and thus the transfer of the F plasmid takes place. Therefore, the recipient procures the F factor and gains the capacity to deliver sex pilus engaged with conjugation.

• Conjugation is a procedure by which hereditary material is moved from one bacterial cell (donor cell or male cell) to another (recipient cell or female cell) through a specific intracellular association called sex pilus or conjugation tube. The maleness and femaleness of a cells are decided by the existence of F-plasmid (likewise called F-factor or sex factor.

F-factor assumes a significant job in conjugation in bacteria. It is this plasmid that presents ‘maleness’ on the bacterial cells; the term ‘sex-factor’ is likewise used to allude to F-plasmid due to this property. F-plasmid is a round ds DNA molecule of 99,159 base pairs.

• Sexual pili (sex pili) are little bar like structures that permit the F-positive (cells that have the F factor) bacterial cells to append to the F-negative (cells without the pili) female to advance conjugative transfer of heredity materials.

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In genetic map of F-plasmid includes one place of plasmid with genes engaged in regulation of DNA replication (rep genes), the other area of the plasmid contains transposable components (IS2, IS3, and Tn1000 genes) and the third huge part, the tra region, comprises of tra genes and has capacity to advance transfer of plasmids during conjugation.

2.  Resistance Plasmid

The resistance plasmid, has the genes for the characteristic antibiotic resistance and shields the host from the antibiotic impacts.

• Additionally, resistance plasmids are a sort of plasmids that convey genes that play a significant job in antibiotic resistance. They are additionally engaged with bacterial conjugation by creating conjugation pili which move the R plasmid from one to other bacteria.

The genes present on R plasmids give protection from antibiotics or other bacterial growth inhibitors. A bacterium with a R plasmid for penicillin resistance can endure treatment by that antibiotic. R plasmids also contain the tra genes that permit the plasmid to spread from cell to cell. The spread of R plasmids represents an undeniable danger to our present capacity to utilize antibiotic agents. Since the resistance genes are found on highly portable plasmids rather than the more stable chromosomes, antibiotic opposition can spread quickly through a bacterial population.

Plasmids are additionally not constrained to specific species, so the antibiotic resistance can spread between species, making bacterial strains that are resistance to numerous regular antibiotic agents.

• Resistance or R plasmids have genes that help a bacterial cell guard against ecological factors, for example, toxic substances or antibiotics. R plasmids when transfer themselves through conjugation process; when this occurs, a new strain of bacteria can get resistant to antibiotic.

R-plasmids ordinarily have genes that code for enzymes ready to destroy and manipulate antibiotics. They are not normally integrated into the host chromosome. Some R-plasmids have just one resistant gene while others can have more upto eight.

Numerous R-plasmids are conjugative have drug resistance qualities as transposable elements, they assume important job in medical or clinical microbiology as their spread through normal population can have significant results in the treatment of bacterial diseases.

Regularly, R-factors code for more than one antibiotic resistance factor: genes that encode resistance from irrelevant antibiotics might be carried on a one R-factor, while sometimes up to 8 unique resistant. Numerous R -factor can transfer with one bacterium then to the next through bacterial conjugation method by which antibiotic resistance spreads between bacterial species, genera and even families. They are a class of conjugative plasmids which advances the bacterial host resistance to particular antibiotics and to some metal ions, including sulphonamide, streptomycin, tetracycline, arsenic, cadmium, mercury, and many more.

R-plasmid comprises of two segments:


• The Resistance Transfer Factor (RTF) helpful for transfer of the plasmid among bacteria, and


• The R-determinants (genes representing antibiotic resistance).

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The structure of resistance plasmid can be commonly depicted as a circular bit of DNA, its length range between 80 – 95 kb and comprises of the major part RTF (Resistance Transfer Factor) molecules. This plasmid is to a great extent homologous to the F factor and contains comparative genes. The R factors differ in their size and in the genes for drug resistance. The R determinant is less in size than the RTF. Both the RTF and R determinant join to shape one unit and are separate from one another by one IS 1 component on either side. The IS 1 components help in the exchange of R determinant between the various types of R-RTF units.

• The resistance plasmids contain genes that can assemble resistance against the antibiotics and help bacteria in the development of Pili.

3.  Virulence Plasmid

At the point when a virulence plasmid is inside a bacterium, it transforms that bacterium into a pathogen, which is a agent of disease or ailment. Microbes that causes disease can be effectively spread and multiply among infected people.

• In contrast with different non-virulent, bacteria that are pathogenic in nature convey genes for virulence factors that permit them to attack and infect their particular hosts.

For a portion of these bacteria, the virulence factors are the consequence of the organisms’ own hereditary material. For example transposons, plasmids are probably the most well-known portable hereditary components. But for others, this is because of hereditary components from extra-chromosomal DNA.

Like different kinds of plasmids, virulence plasmids can likewise be transmitted starting with one bacterium then into the next. Other than virulence gene, plasmids have also been able to convey other significant components that improve transmission and maintenance of the bacterial cell.

Concerning pathogenicity, virulence plasmids play a significant role as they can help bacteria successfully adjust to their respective environments. This is because the virulence plasmid can empower the organism to communicate a variety of related virulence-associated functions providing the organism with characters advantageous to survive in environment.

• They make the bacterium increasingly pathogenic as the bacterium is better ready to oppose host defence or to produce toxins.

4.  Col-plasmid

The col plasmid is another small sort of plasmid contains the DNA segments for Col which encodes the colicin, this protein shields the bacteria from the other pathogenic assaults. The col plasmid helps in protecting the host. Col-plasmids have genes that give capacity to the host bacterium to destroy other bacteria by producing bacteriocins, a sort of proteins. Bacteriocins frequently destroy cells by making channels in the plasma membrane by this way expanding its permeability. They may sometimes also corrupt DNA or RNA or act on peptidoglycan and weaken the cell wall.

Bacteriocins act just against close strains of bacteria. Col E1 plasmid of E. coli code for the production of bacteriocin called colicins which kill other strains of E. coli. Col plasmids of some E. coli code for the production of bacteriocin, to be specific cloacins that kills Enterobacter species.

• Col plasmids comprises of gene that make bacteriocins (also known as colicins), which are proteins that destroy other bacteria and act as a defence for the host bacterium.

A couple of examples of Col plasmids includes Col B, Col E2 and E3. Their differences are described by their mode of action. These toxins influence the particular bacteria by affecting the procedures of replication in DNA, Translation and their metabolism.

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Like F plasmids, a portion of the Col plasmids have been shown to convey components that upgrade their transmission from one cell to the other. Through the mating procedure or conjugation, especially for cells with the F factor, the Col plasmids can be passed from one cell (donor) to another (recipient). Accordingly, the recipient gets the capacity to produce poisons or toxins that kill or repress the growth of target bacteria which do not possess the col plasmid.

5.  Degradative Plasmid

Degradative plasmids (also known as Metabolic plasmids) have coded enzymes that debase unusual substances, for example, toluene (aromatic compounds), pesticides and some sugars (lactose).
Some metabolic plasmids occur in specific strains of Rhizobium and influences nodule development in leguminous and complete fixation of nitrogen.

• Degradative plasmids, enables the processing of unusual substances to digest, for example toluene and salicylic acid xylene.

Degradative plasmids help the host bacterium to breakdown compounds that are not usually found in nature, for example, camphor, xylene, toluene, and salicylic acid. These plasmids contain genes for unique enzymes that separate or breakdown specific compounds.
Degradative plasmids are conjugative in nature.

Contrasted with different kinds of plasmids, degradative plasmids permit the host organism to breakdown/separate xenobiotic compounds. Xenobiotic compounds comprises of a compounds discharged into the environment because of human activities and are not naturally present in nature.

While degradative plasmids add to the debasement of xenobiotic intensifies, their conduct changes relying upon various factors, for example, the limit with respect to replication and solidness.

The distinctions in the behaviour of various degradative plasmids rely upon various factors such as ability of replication and stability. In this manner distinct behaviour results in them and their respective hosts.

• The utilization of biodegradative microorganisms for the purpose of expelling out the Xenobiotic compounds from the environment is known as Bioaugmentation.

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