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Binary fission Definition, Types, Steps, Examples

Binary fission can be described as a kind of sexual reproduction in which one living cell, or organelle expands twice its size,...

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This article writter by MN Editors on November 22, 2021

Microbiology Notes is an educational niche blog related to microbiology (bacteriology, virology, parasitology, mycology, immunology, molecular biology, biochemistry, etc.) and different branches of biology.

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Binary fission Definition, Types, Steps, Examples
Binary fission Definition, Types, Steps, Examples

Definition of binary fission (What is binary fission?)

Binary fission can be described as a kind of sexual reproduction in which one living cell, or organelle expands twice its size, and then splits into two identical cells, which means that each of the daughter cells can be expected to grow to what size as the organelle or cell.

  • Binary fission is distinct from other forms of fission by the fact that only two components are created from one entity.
  • This kind of reproduction is known as asexual since the process does not involve the creation or fusion of gametes.
  • Since binary fission is one of the types of asexual reproduction daughter cells that are created have similar genetic content to the parent cell.
  • Binary fission is a method of reproduction found in many prokaryotes like archaea the cyanobacteria family, eubacteria, as well as certain eukaryotes such as amoeba and paramecium.
  • Certain cell organelles, such as mitochondria are also subject to cell division through the process of binary fission.
  • In order to be functional and compete, the bacterium has to split at the right time and in the proper spot, and supply each offspring with a full duplicate of its vital genetic material.
  • While the concept of binary fission has a lot in common with mitosis, there are a couple of major differences between them. While binary fission is a method for propagation utilized by bacteria and archaea, mitosis is a process that occurs in the eukaryotic cell.
  • Additionally, both happen for different reasons within cells. Both processes are characterized by a series of stages that involve DNA division and then the splitting of cells into two daughter cells.
  • A few eukaryotes such as paramecium or amoebae may utilize binary fission as a way for propagation.

Steps/Process of Binary Fission

Binary fission in prokaryotes

  • Prior to binary fission, in contrast to human cells where the genetic material is located in the nucleus, the genetic material of the prokaryotes (chromosomes) is found in a specific area of the cell inside the cytoplasm, known as the nucleoid.
  • The chromosomes undergo replication that begins at a specific place in the chromosome known as the source of replication. The origin splits and as the process continues the two sources move to opposite sides of the cell by pulling the chromosomes together to them.
  • After the replication has been completed the various proteins that function as cells division machinery are assembled at the site of division to be used for future division (at the middle in the cells).
  • One of the proteins that are essential involved in this process is the FtsZ protein that forms rings-like structures in the cell’s center.
  • This procedure is crucial in order to make sure that this division does not split the cytoplasm but doesn’t harm genes.
  • In order to allow separation of the cytoplasm the membrane pinches upwards and the septum (new wall of the cell) that forms in through the central part of the cells.
  • In the end, the septum splits into two separate cells.
  • Crenarchaeota does not have cells or a wall, nor FstZ. FstZ protein, but makes use of a basic mechanism with different proteins known as the ESCRT-III mechanism.
Binary fission in prokaryotes
Image Source: https://upload.wikimedia.org/wikipedia/commons/thumb/0/02/Binary_Fission_2.svg/440px-Binary_Fission_2.svg.png

Binary fission in eukaryotes

  • Although the majority of eukaryotes reproduce sexually, however, certain protozoans such as amoeba reproduce through binary fission, and cell division within certain organelles inside cells of eukaryotes occurs in a similar manner to bacteria.
  • The procedure of binary fission within these cells is exactly the same as that of prokaryotes, which involves an FtsZ protein.
  • Organelles in cells like chloroplasts and mitochondria divide through binary fission, which is the foundation of the Endosymbiotic theory that explains why prokaryotes evolved into mitochondria in the modern-day.

Types of binary fission

Binary fission can be classified into four classes based on the plan of division in the cytoplasm

Irregular Binary Fission

In this instance, the division of cells (cytokinesis) is possible in any direction, but it is generally perpendicular to the plane of division of the chromosomes (karyokinesis). This is a common phenomenon in living organisms like amoeba.

Transverse Binary Fission

Transverse Binary Fission is cytokinesis that occurs on the transverse axis of the cell. This kind of division can be observed in protozoans that are ciliated, such as Paramecium.

Longitudinal Binary Fission

The division of cytoplasm takes place along the longitudinal direction that runs through the cells. This type of division happens in flagellates, such as Euglena.

Oblique Binary Fission

Cell division in this instance happens by oblique means (i.e. left and right left and right). This type of division can be found in dinoflagellates, such as Ceratium.

Examples of organisms that use Binary Fission

  • A variety of organisms, which include both eukaryotes and prokaryotes. split by binary fission.
  • The majority of bacteria reproduce through this method. The process involves division using an FtsZ protein, which includes the process of chromosomal reproduction, chromosomal separation and cell splitting.
  • In protozoans, such as amoeba, Paramecium, Euglena However, the procedure may differ for the division of cells and also in the way the cell divides.
  • Organisms that reproduce via binary fission comprise Bacillus subtilis B. cereus, B. pumilus, Escherichia coli, Clostridium perfringens Corynebacterium diphtheriae Amoeba, Paramecium, Euglena, Ceratium, etc.

Binary Fission in Paramecium (Asexual Reproduction)

  • Paramecium is one of the genus made up of ciliates like Paramecium Aurelia Paramecium bursaria, and Paramecium caudatum to name a few.
  • Paramecia (members of the genus paramecium) are shaped like the sole of a shoe or slipper. They are protected by cilia which permit them to go from one location in one direction and feed.
  • Contrary to Bacteria, Paramecium, unlike Bacteria, is made up of eukaryotic cells, which indicates that they are well-organized. While Paramecia is able to reproduce sexually but Asexual reproduction (binary fission) is the main method of reproduction, which occurs under the right conditions.
  • For Paramecium Asexual reproduction occurs through the transverse binary fission. The organism is comprised of two nuclei (a large macronucleus as well as one small micronucleus) it is the smaller nucleus which is involved in reproduction.
  • In favorable environmental conditions (water etc.) the ciliate ceases to feed as the oral groove is dissolved. This is followed by the micronucleus splitting into two, and the two micronuclei advancing towards the poles within the cell.
  • After the small nucleus has divided, the macronucleus splits into two, and then both relocate to the opposite one of them. In the end, cytokinesis takes place on the transverse axis, which allows it to create two identical cells (This is the result of the cytoplasm splitting in a straight line towards the longitudinal axis the cells).
  • Paramecium’s micronucleus divides via mitosis whereas the larger nucleus splits through amytosis. In this case, the genetic material within the nucleus (micronucleus) splits via mitosis. The nucleus is divided into four phases of mitosis which include metaphase, prophase anaphase, and telophase.
  • In the micronucleus’s division process and duplication, all energy is used to split and duplicate. This is why cell growth is not happening at this point.
  • While Paramecium is also a complicated method for sexual reproduction, binary fission takes place when couples (conjugant) are separated.

Binary Fission in Bacteria

Bacteria utilize a variety of sexual reproduction. This includes:

  • Binary fission
  • Zoogloea stage
  • Conidia and gonidia form the basis of the formation
  • Budding
  • Fragmentation

While different kinds of bacteria are able to use one or more of the methods mentioned above Binary fission is the most commonly used method of Asexual reproduction that happens when the environment is favorable (water and optimal temperature range , etc.).

Binary fission in bacteria has two major stages, which comprise:

Replication of the genome

  • The process of binary fission begins with the replication of the genome (bacterial nucleoid’s chromosome). 
  • In this case, replication enzymes copy the chromosome’s beginning at the point of replication, and then continue to separate the string into two.
  • Replication results in two daughter cells that are circular as the cell expands. The cells’ origins move towards either end of the cell when DNA copying occurs.

Septum cell division and formation

  • During this time, the plasma membrane’s peripheral membrane ring opens up and divides the cell into two. This is accompanied by the creation of a double membrane septum, before the two cells split into two identical cells.
  • Contrary to Paramecium and division the nucleoid’s nucleoid does not require mitosis.
  • If the environment is conducive the binary fission process can take around 30 minutes.
  • Binary fission is subject to a broad range of environmental modifications. This is why other types of asexual reproduction are able to the fore in adverse environmental conditions.

Binary Fission in Amoeba

  • Amoeba is a genus consisting of such eukaryotic organisms as Amoeba proteus. Amoebae lack a definite shape and move through temporary projections known as pseudopodia (false feet).
  • As with other eukaryotes, the cytoplasm as well as the contents of the cells of Amoebae are stored within a cell membrane, while DNA is located within the nucleus.
  • For certain species like Amoeba proteus Sexual reproduction occurs by binary fission (a type of sexual reproduction that is asexual). It can be accompanied by multiple fission or the sporulation.
  • Similar to Paramecium which is also an Eukaryote, genetic material gets duplicated by mitosis. The DNA strand is passed through four phases that occur during the process of mitosis (prophase the metaphase phase, prophase, and telophase).).
  • When telophase is over two daughter nuclei have formed, with a lattice underneath each membrane of the nuclear. The nucleus division process occurs in conjunction with cytokinesis that divides the cytoplasm , and eventually creates two daughter cells which are nearly identical in terms of cell content.
  • In contrast to bacteria multipolar nuclear spindle is made during binary fission of amoeba.
  • Reproduction in amoeba is accomplished via an irregular binary fission. Cytokinesis is a process that occurs on the plane parallel to the karyokinesis plane.
Binary Fission in Amoeba
Binary Fission in Amoeba | Image Source: https://farm6.staticflickr.com/5660/23270601065_e0d6c087f1_o.jpg

Differences between Binary Fission and Mitosis (Binary Fission vs Mitosis)

In addition to it being true that binary fission is a common occurrence among prokaryotes and mitosis is common in eukaryotes. Some of the important distinctions between these 2 methods used to divide cells are:

  • Spindle apparatus are formed in mitosis (to separate the chromosomes) they are not created during the binary fission process.
  • Eukaryotes contain cell organelles that double during interphase the process of preparing for mitosis. However, considering that prokaryotes are more primitive cells, only ribosomes and a few other cell components grow in number prior to the time that the binary fission process begins.
  • While binary fission is primarily employed as a method of reproduction by prokaryotes Mitosis can be used for a variety of purposes, which include replacement of cells, growth, and the growth of the living organism.
  • Because of the complexity of the eukaryotic cells, mitosis can take more time than binary fission. Binary fission happens rapidly.
CharacteristicsBinary FissionMitosis
OccurrenceThis happens in prokaryotes and a few eukaryotes.This is only found in eukaryotes.
MechanismIn binary fission the spindle fibers do not get created.In mitosis, the division process is made possible by the development by spindle fibers.
StagesBinary fission is a process that involves three phases that are chromosome replication as well as chromosomal segregation. splitting of the cytoplasm.Mitosis has four stages: metaphase, prophase and telophase.
ProductThis results in the creation from two cells that are identical each with the same genetic material as the parent cell.The process also leads to the development from two cells that are identical each with the same genetic material as the parent cell.
FunctionBinary fission is a form of reproductive asexuality.Mitosis plays a role in the cell’s growth (numbers) in multicellular organisms.
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