Anabaena

Basic information about Anabaena

1. Algae : Anabaena Prepared by: Md. Shakiur Rahman ID: 170711 Biotechnology and Genetic Engineering Discipline Khulna University,Bangladesh .

2. What is Anabaena? Anabaena is a genus of filamentous cyanobacteria, or blue-green algae. Fig: Anabaena

3. Structure of Anabaena It has filamentous structure. Its filament resembles the filament of Nostoc . The filaments of Nostoc are covered by mucilage and form a colony which is absent in Anabaena. The filament of Anabaena consists of string of beaded cells. Several intercalary heterocysts are present in the trichome. Heterocysts are of same shape as of vegetative cell. The filaments are ordinarily straight. But they may be circinate or irregular. Filaments occur singly within a sheath. Sheaths are always hyaline and watery gelatinous.

4. Structure of cells of Anabaena The cells are spherical or barrel shaped. They are rarely cylindrical and never discoid. The majority of the cells of a colony are similar in size. Its cells have following components: Each cell has outer cell wall. This wall consists of three layers. The inner layer is thin cellular layer, medium is pectic layer and outer is mucilage layer. The peripheral of the protoplasm is composed of part called chromoplasm . It contains pigment. Hence it is colored. The central colourless part of protoplasm contains nucleus like material called central body or chromatin granules. Heterocysts are of same shape as of vegetative cell. Golgi bodies, encoplasmic reticulum and mitochondria are absent in their cells.

5. Heterocysts are the point at which the filament breaks into hormogones . Heterocysts convert nitrogen into ammonia. Hormogones may also formed by the breaking of filament or decay of filament at some other points.

6. Occurrence of Anabaena Anabaena is found as plankton. They form symbiotic relationships with certain plants, such as the mosquito fern. Some species of Anabaena are endophytes. They live in the roots of Cycas and Azolla . Anabaena is found in all types of water. Blooms or massive growths can occur in waters with a lot of nutrients. These blooms discolor the water and give it a bad odor when the cells die and decay.

7. Characteristics of Anabaena Anabaena is a genus of filamentous cyanobacteria that exist as plankton. They perform oxygenic photosynthesis. They are heterocyst forming and photoautotrophic. During times of low environmental nitrogen,about one cell out of every ten will differentiate into heterocyst. They are known for nitrogen-fixing abilities, and they form symbiotic relationships with certain plants, such as the mosquito fern. They are one of four genera of cyanobacteria that produce neurotoxins, which are harmful to local wildlife, as well as farm animals and pets. Production of these neurotoxins is assumed to be an input into its symbiotic relationships, protecting the plant from grazing pressure.

8. Importance of Anabaena It is believed that cyanobacteria on Earth are responsible as being the producer for most, if not all, the oxygen in the atmosphere. Plants also produce oxygen, however, they depend on chloroplasts. These plant organelles are believed to have been derived from the cyanobacteria. The Anabaena variabilis strain has been extensively studied because it also undergoes a process where it produces hydrogen gas by using sunlight. This product could provide a reusable source of energy. By further studying the genome and understanding the process, the hydrogen gas could be mass produced and used as fuel or energy.

9. Certain species of Anabaena have been used on rice, paddy fields. They act as natural fertilizer. The cyanobacteria seem to have been the foundation of changing the Earth’s atmosphere because it takes care of half of the Earth’s photosynthesis. A more recent study indicated that the Phenylalanine ammonia lyase (PAL), could be a potential solution to the disease known as phenylketonuria. Current research is being done on the possible effects on animals and how they would carry over to humans.

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