Important Topic Of Biology: Binary Fission

It is a simple & common method of asexual reproduction. In this method, a single-celled organism divides into two daughter cells and then each daughter cell develops into a new individual. This process happens with the division and duplication of the parent’s genetic matter into two parts.

Types of Binary Fission:

1. Simple Binary fission
2. Longitudinal Binary fission
3. Oblique Binary fission
4. Transverse Binary fission

Examples of Binary Fission

Both prokaryotes and eukaryotes are divided by binary fission.

• Most of the bacteria reproduce by this process. The process involves the division by utilizing the FtsZ protein, including chromosomal replication, chromosomal segregation, and cell splitting.
• In protozoans like amoeba, Paramecium, Euglena, however, the process might differ in cell splitting and in how the cytoplasm divides.
• Organisms that reproduce by binary fission include Bacillus subtilis, B. cereus, B. pumilus, Escherichia coli, Clostridium perfringens, Corynebacterium diphtheriae, Amoeba, Paramecium, Euglena, Ceratium, etc.

Additional Information of Binary Fission

• In this process, each daughter cell receives one copy of its parent DNA. It is a primary method of reproduction in prokaryotic organisms.
• Binary Fission occurs without any spindle apparatus formation in the cell. In this process, the single DNA molecule begins replication and then attaches each copy to various parts of the cell membrane. When the cell starts to get drawn apart, the original (actual) and replicated chromosomes get apart.
• The process of binary fission is usually rapid, and its speed varies among species. The time required by organisms to double their number of cells is called doubling time.
• Each species requires specific conditions for its growth. These conditions include pH levels, temperature, oxygen, light, moisture, osmotic pressure. For instance, mesophiles thrive at moderate temperatures ranging from 20 °C to 45 °C. The ambient temperature of the human body is 37 °C, which means many of the disease-causing bacteria are mesophiles.

Mycobacterium tuberculosis is the bacterium that causes tuberculosis in humans. It divides every 15 to 20 hours, which is very slow when compared to other pathogenic bacteria such as Escherichia coli, which can divide every 20 minutes.

On the other end of the spectrum are the extremophiles. These bacteria can survive extremely harsh conditions such as high temperatures, high salinity, highly acidic environments, and more. For instance, the Deinococcus radiodurans is an extremophilic bacteria that can survive a thousand times more radiation than a person can. Under normal circumstances, it can divide every 48 hours. However, when exposed to harsh conditions like drought, it can slow down its growth rate until more favorable conditions arise.

Key Features of Binary Fission

1. Asexual Process: Involves only one parent organism, with no exchange of genetic material.
2. Equal Division: The parent cell splits into two nearly identical daughter cells.
3. Rapid Process: Binary fission occurs quickly, enabling organisms to reproduce efficiently under favorable conditions.

Steps in Binary Fission

1. DNA Replication:
   • The circular DNA of the organism is copied.
   • This ensures that each daughter cell receives a complete set of genetic material.
2. Growth of the Cell:
   • The parent cell elongates, and the replicated DNA molecules move to opposite ends of the cell.
3. Septum Formation:
   • A septum (division wall) begins to form at the center of the cell, dividing it into two sections.
4. Cytoplasmic Division:
   • The cytoplasm splits, and the cell membrane pinches inward, resulting in two separate daughter cells.
5. Formation of Daughter Cells:
   • Two identical daughter cells are produced, each containing a copy of the parent’s DNA.

Limitations of Binary Fission

1. No Genetic Variation: Since it is asexual, the daughter cells are clones, reducing genetic diversity.
2. Vulnerability to Changes: Identical offspring are more susceptible to environmental changes and diseases.