Anabaena - Classification, Structure, Function and Example

Anabaena: Anabaena is a blue-green algae distinguished from green algae by a number of key characteristics. Unlike green algae, Anabaena cells do not have a distinct nucleus, and the pigment is distributed throughout the cell. Anabaena contains both green chlorophyll and blue pigment. Anabaena appears morphologically as a filament that resembles a string of beads, with larger, empty cells in between. Nostoc also produces bead-like filaments, but they are encased in a gelatinous mass. NEET Biology Notes on Anabaena are provided in the article below.

Free Study Material for NEET Preparation

Anabaena Meaning

Explore - NEET Online Courses by PW

Anabaena Classification

Cell The Unit of Life

Anabaena Structure

1. Filaments (Trichomes): Anabaena exhibits a filamentous architecture, consisting of chains of cells known as trichomes. These chains resemble strings of beads, with each "bead" being a cylindrical, photosynthetic cell. The trichomes can be either straight or slightly curved.
2. Vegetative Cells: Predominantly, the cells within a trichome are vegetative cells. These cells perform photosynthesis, harnessing sunlight, water, and carbon dioxide to generate energy and produce glucose for the organism. Additionally, they contain gas vesicles that facilitate Anabaena's buoyancy in water.
3. Heterocysts: Interspersed along the trichomes are specialized cells called heterocysts. These cells are larger and possess thicker walls compared to vegetative cells. Heterocysts are the sites of nitrogen fixation, a process that transforms atmospheric nitrogen (N2) into ammonia (NH3), which the organism can utilize. To protect the nitrogenase enzyme, which is responsible for nitrogen fixation, from inactivation by oxygen (O2), heterocysts develop a thick cell wall and limit the oxygen permeability.

Structural Organisation in Animals

Anabaena Characteristics

1. Filamentous Structure: Anabaena forms elongated, chain-like structures known as trichomes. These trichomes consist of a series of bead-like cells arranged in a linear fashion.
2. Nitrogen Fixation: Anabaena possesses the unique ability to fix atmospheric nitrogen. This process involves converting nitrogen gas (N₂) from the atmosphere into ammonia, a form that plants and other organisms can readily utilize.
3. Heterocysts: Within the trichomes, Anabaena develops specialized cells called heterocysts, which are crucial for nitrogen fixation. Heterocysts are distinguished by their larger size and paler appearance compared to other cells. These cells maintain an anaerobic environment necessary for the nitrogen fixation process.
4. Photosynthesis: Anabaena is capable of photosynthesis, allowing it to produce its own food by harnessing sunlight.
5. Symbiotic Relationships: Anabaena can engage in symbiotic relationships with certain plants, such as the mosquito fern. In these mutualistic interactions, Anabaena supplies the plant with fixed nitrogen, while the plant provides a sheltered habitat for Anabaena.
6. Toxin Production: Some Anabaena species can produce toxins detrimental to animals and humans. These toxins may cause a range of health issues, including liver damage, respiratory distress, and skin irritation.
7. Freshwater Habitat: Anabaena is prevalent in various freshwater environments, including ponds, lakes, and rivers, and can also be found in moist soil.
8. Blooms: Under conditions of nutrient enrichment, Anabaena can proliferate rapidly, leading to blooms. These blooms may discolor the water and create conditions that are inhospitable for other aquatic organisms.

Anabaena Functions

• Heterocysts: Specialized cells with thick walls that create an oxygen-free environment.
• Nitrogenase Enzyme: Breaks the triple bond in atmospheric nitrogen (N₂) to convert it into ammonia (NH₃), which is a usable form of nitrogen. The enzyme is highly sensitive to oxygen, necessitating the oxygen-free environment.
• Usage: Ammonia produced is incorporated into amino acids and other nitrogenous molecules by Anabaena and other organisms.

2. Photosynthesis:

• Vegetative Cells: Non-specialized cells that contain chlorophyll pigments.
• Process: Uses sunlight, water (H₂O), and carbon dioxide (CO₂) in the Calvin cycle to produce carbohydrates (sugars) for energy and growth.
• Byproduct: Releases oxygen gas (O₂) into the environment.

3. Ecological Role:

• Nitrogen Cycle: Anabaena's nitrogen fixation replenishes usable nitrogen in aquatic ecosystems.
• Symbiosis: Forms mutualistic relationships with plants like the Azolla fern, providing fixed nitrogen in exchange for a protected environment.
• Toxin Production: Some species can produce toxins under specific conditions, but the focus here is on their beneficial ecological roles.

Anabaena Prokaryotic or Eukaryotic

1. They can be single-celled or form colonies.
2. They do not have a nucleus; their DNA is free-floating in the cytoplasm.
3. They lack membrane-bound organelles.
4. Their cell wall is simple and made of peptidoglycan.

Anabaena Examples

1. Anabaena azollae

Medulla Oblongata

2. Anabaena variabilis

3. Anabaena flos-aquae

Bones in Human Body

4. Anabaena cylindrical:

5. Anabaena sphaerica :

Female External Genitalia

Anabaena Reproduction

1. Fragmentation:

2. Akinete Formation:

Economic Importance of Algae

3. Heterocysts: