There are two basic types of cells — prokaryotes, suchcas bacteria and the more complex eukaryotes. Depending on the organism, eukaryotes have many different modes of reproduction, including mitosis and meiosis. Amoebae are the eukaryotic exception, reproducing by binary fission.
Prokaryotic cells, such as bacteria and Archaea, are smaller, simpler and more evolutionarily primitive than eukaryotes are, and have only one option for reproduction, binary fission, which is also referred to as prokaryotic fission.
What Is Binary Fission?
Binary fission is a type of cell division in which a parent cell copies it’s genetic material, and then divides, transforming into two daughter cells, each new cell having one complete copy of the genetic instructions necessary to run the cell.
The Steps of Binary Fission
- The parent cell grows to its maximum size.
- The cell duplicates its chromosome (a process called replication) so that two exact copies of the genetic material exist inside the parent cell. These two molecules of DNA are attached to the cell’s plasma membrane.
- The cell then grows, increasing the distance between the two duplicated chromosomes that are attached to the plasma membrane.
- In prokaryotes (bacteria and Archaea), a new cell wall, called a septum, begins to grow across the middle of the cell, bisecting it. Amoebae, which do not have a cell wall, develop a cleavage furrow that pinches the cell in half.
- After the septum forms completely, depending on the type of microbe, the daughter cells may remain attached to each other, or may completely separate. Whether attached or separated, each cell is an independent unit.
- This process repeats, sometimes very quickly, such as in E. coli bacteria which divides every 15 minutes, or very slowly, such as in Mycobacteria leprae, the causative agent of leprosy, which only divides once every two weeks.
Binary Fission and Exponential Growth
Through the process of binary fission, one parent cell divides into two daughter cells and then each daughter cell of the following generation repeats the process…one cell leading to two, two to four, four to eight, and so on. This is called logarithmic or exponential growth, and depending on the generation time of the organisms (time between cell divisions), this strategy can result in very rapid population growth. For example E. coli, which has a short generation time, using binary fission, can go from one cell to a visible colony or millions of cells in a day.
For more information on microbiology, see the Virtual Microbiology Classroom of the science education website Science Prof Online.
Sources
Bauman, R. (2010) Microbiology. Pearson Benjamin Cummings.
Perry, J. and Stanley, J. (1997) Microbiology Dynamics & Diversity. Saunders College Publishing.
Starr, C. & Taggart, R. (1992) Biology: The Unity and Diversity of Life. Wadsworth Publishing.
Tami Port - Tami Port is a college professor of cell and microbiology and creator of ScienceProfOnline.com, a free science education website.
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