Binary Fission (Meaning and Explanation)

We explain what binary fission is, its stages, the types that exist and various examples. Also, other forms of asexual reproduction.

binary fission asexual reproduction amoeba — Amoebas reproduce by irregular binary fission, separating their rhizopods.

What is binary fission?

Bipartition or binary fission It is a mechanism of asexual reproduction of unicellular living beings typical of prokaryotes, that is, bacteria and archaea. It consists of the duplication of the individual's cellular DNA, as a previous step to the division of the cytoplasm in two. So, gives rise to two daughter cells with identical genetic material.

This is the most common form of reproduction in the bacterial world. In some species it can occur at an impressive speed (a bacteria Escherichia coli can be divided once every 20 minutes), as long as the conditions of the surrounding environment are adequate.

In addition to rapid colonization of the environment, this reproductive rate has adaptive purposes: with this reproductive rate, the mutation rate is usually high. This produces new bacterial strains better adapted to the environment (for example, more resistant to antibiotics). This is partly the reason for the great evolutionary success of bacteria, present throughout the world.

Binary fission takes place through a series of stages:

DNA is replicated to create an exact copy of itself.
Each set of DNA oriented towards an opposite region of the cell. Cellular organelles are also replicated.
The FtsZ protein is activated, which forms filaments around the division axis of the cell. These filaments make the membrane grow into the cytoplasm, narrowing the cell.
A septum (or waist) is formed that gradually narrows until completely separates the cytoplasm into two thus forming two identical individuals (daughter cells), but with independent life.

Types of binary fission

There are several forms of binary fission possible, depending on the way the single-celled organism divides itself:

Regular When the cell divides symmetrically.
Irregular or amoeba type When the divisions occur in rhizopods (“fingers”) or in a disordered manner.
Longitudinal When the cell divides from its horizontal axis.
Cross When the cell divides perpendicular to the axis of the cell spindle.
Oblique When the cell divides longitudinally at first, but then becomes transverse.

Examples of binary fission

binary fission types longitudinal asexual reproduction — Protozoa that reproduce asexually do so through binary fission.

There are plenty of examples of this type of reproduction. Most prokaryotic organisms and some eukaryotes use it. In fact, the fight against bacterial infections is so arduous because their bipartition rate is high. Thus, they reproduce by binary fission:

The bacteria of all types and genres, such as the aforementioned Escherichia coliand archaea like the Extremophila Methanobacterium bryantii.
primitive eukaryotes like him Crypthecodinium cohnii or the species of paramecium.
Some protozoans like the amoeba (Amoebidae).

Other types of asexual reproduction

Non-sexual reproduction mechanisms are those that involve a single individual. Therefore, they have little or no genetic variation. In addition to binary fission, these types of reproduction include:

Gemmation The parent forms extensions or prominences of its body. Eventually, these extensions can separate from it and have a life of their own. In other cases, they continue together and start a colony. When it occurs at the cellular level, it is asymmetric mitosis.
Sporulation It consists of the production within the cell or in specialized organs (sporangia, for example), of cells wrapped in a super-resistant covering, known as spores. These are capable of surviving long periods and very hostile conditions, and then producing a new individual when the environment is favorable.
Parthenogenesis The new individual is created from the development of unfertilized female sex cells. Therefore, it is genetically equal to the parent. Some animals can do it, such as flatworms, rotifers, tardigrades, insects, amphibians, fish and crustaceans, but also some reptiles.