Cyanobacteria - Blue-green algae : Monera

Introduction to Cyanobacteria (Blue-green algae)

Cyanobacteria is also known as blue-green algae

Classification

Kingdom: Monera

Division: Eubacteria

Class: Cyanobacteria

Order: Nostocaceae

Genus: Nostoc

Common name: Star jelly

General characters of Cyanobacteria

• The incipient nucleus is present.
• The presence of a 70s type of ribosome.
• The gas vacuole is present.
• They are autotrophic and photosynthesis takes place by oxygenic photosynthesis.
• Double membrane-bound cell organelles like ER, Golgi body, plastids are absent.
• Their is an absence of locomotory organelles.
• Sexual reproduction is absent.
• Reproduction takes place by means of the asexual method.

Economic Importance of Cyanobacteria

• Species of Nostoc and Anabanahelp in nitrogen fixation.
• Nostoc species can be used as a protein rich food.
• Species areLyangbiacan be used in the preparation of antibiotics.
• Cyanobacteria occurring in wall and roof of houses in rainy season causes corrosion.
• Some species of cyanobacteria can secrete toxic chemical substances which cause poisoning in aquatic animals. Eg; Microcystis
• Cyanobacteria performs the oxygenic photosynthesis and they are the chief producers of the biosphere.
• If the alkaline land is made water-logged then there is the growth of the blue-green algae which enhance the fertility of the soil.

Archaebacteria

The most primitive and ancient bacteria is known as archaebacteria. These are supposed to be the oldest of the living fossils.

Characteristic of Archaebacteria

• They posses a unique cell wall that consists of polysaccharide and protein.
• They lack peptidoglycan( murein).
• The cell membrane contains branched-chain lipids, which enable them to withstand extremes of heat, high pH, an absence of oxygen and high salt concentration.

Based on ecological properties, the archaebacteria can be classified into three groups:

Thermoacidophiles

They are aerobic forms of bacteria found in hot sulphur springs. They are high temperature and acid loving cyanobacteria. Under aerobic conditions, these sulphur-dependent bacteria are called thermoacidophiles. They can reduce sulphur to H₂S under anaerobic conditions.

Methanogens

These are anaerobic archaebacteria which occur in marshy places and convert the formic acid or CO₂ to methane. In biogas plants, they produce the methane gas, which is used as a fuel.

Halophiles

These are anaerobic bacteria which occur at salt rich in soils. They prepare pigmented membrane in the presence of sunlight. This process is different from that of eukaryotic photosynthesis.