What is binary fission? Types, Examples

What is binary fission?

Bipartition or binary fission is a mechanism of asexual reproduction of unicellular living beings, typical of prokaryotes, that is, of bacteria and archaea. It consists of the duplication of the individual’s cellular DNA, as a previous step to dividing the cytoplasm in two. Thus, it 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 rate (an Escherichia coli bacterium can divide once every 20 minutes), as long as the conditions of the surrounding environment are suitable.

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

What is binary fission? Types, Examples
What is binary fission? Types, Examples

Binary fission takes place through a series of stages :

  • DNA is replicated to create an exact copy of itself.
  • Each set of DNA faces an opposite region of the cell. Cell organelles replicate as well.
  • The protein FtsZ is activated, which forms filaments around the axis of the division 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 it completely separates the cytoplasm in two, thus forming two identical individuals (daughter cells), but living independently.

Types of binary fission

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

  • Regular.  When the cell divides symmetrically.
  • Irregular or amoeba type.  When the divisions occur in rhizopods (“fingers”) or a disorderly 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

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

  • Bacteria of all types and genus, such as Escherichia coli , and archaea, such as the Extremophilic Methanobacterium bryantii.
  • Primitive eukaryotes such as Crypthecodinium cohnii or paramecium species.
  • Some protozoa 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:

  • Budding. The parent forms extensions or prominences of its body. Eventually, these extensions can separate from him and have a life of their own. In other cases, they stay 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. They can survive long periods and very hostile conditions, and then produce a new individual when the environment is conducive.
  • 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 perform it, such as flatworms, rotifers, tardigrades, insects, amphibians, fish, and crustaceans, but also some reptiles.

What is binary fission? Types, Examples

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