Cyanobacteria: Overview, Structure, Diagram, Examples, Uses, Cyanobacteria

Cyanobacteria definition: Cyanobacteria or blue-green algae are bacteria belonging to the phylum of bacteria that synthesize their energy from the process called photosynthesis. They are known for their distinctive blue-green colour and are among the first organisms to produce oxygen on Earth. Cyanobacteria are essential in ecosystems, they form the base of many aquatic food chains. Cyanobacteria is a topic of the chapter Biological Classification in Biology.

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This Story also Contains

1. What are Cyanobacteria?
2. General Characteristics of Cyanobacteria
3. Classification and Cyanobacteria Types
4. Habitat And Distribution
5. Photosynthesis in Cyanobacteria
6. Ecological and Environmental Significance
7. Recommended video for Cyanobacteria

What are Cyanobacteria?

Cyanobacteria is among the first microorganisms that were ever formed on the planet Earth with a fossil record estimate of about 3 billion years of age. 5 billion years. It is needed to recognise cyanobacteria, as they are the world’s most diverse group of bacteria that can perform oxygenic photosynthesis, and therefore being critical to the biosphere, oxygen producers can significantly define the first Earth’s atmosphere.

Traditionally, cyanobacteria are of great importance to the history of life because they played the role of the Great Oxidation Event, through which the majority of aerobic organisms appeared. These characteristics reveal their flexibility and significant function in ecological and evolutionary research as they have numerous forms and environments.

General Characteristics of Cyanobacteria

The characteristics of cyanobacteria are defined as:

Morphological Features

Cyanobacteria present themselves in many forms; they may be isolated, colonial or filamentous. They commonly exist as surface substratum and are attached to objects or substratum; they form mats or biofilm in aqueous surroundings, demonstrating their structural diversity in various ecosystems.

Cyanobacteria structure

Cyanobacteria contain a basic floating cell structure, these cells are prokaryotic and do not contain membrane-bound organelle. In addition, they have a detailed change in the composition of their cell walls, they have a peptidoglycan layer and a thylakoid membrane where photosynthesis is carried out.

Pigments and Colouration

Their pigments are chlorophyll a phycobiliproteins and carotenoids giving cyanobacteria their typical blue-green colour. These pigments are very vital in the absorption of light energy which is crucial in the photosynthesis process.

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Classification and Cyanobacteria Types

The classification and types of cyanobacteria are described below-

Taxonomy and Classification

Cyanobacteria comes under the domain bacteria and is a phylum within the said domain. They are classified depending on the genetic and phenotypic features; cytoplasmic organisation, colouration and metabolic versatility.

Kingdom and Phylum Details

Cyanobacteria as classified falls under the kingdom bacteria and the phylum cyanobacteria. Among bacteria, they are special because they can carry out oxygenic photosynthesis, as plants and algae do.

Classification Hierarchy

Thus, in the phylum Cyanobacteria there are several orders, families, genera and species. Principal orders are Chroococcales, Nostocales and Oscillatoriales; their members can be unicellular or form filaments, though the form varies in each order.

Habitat And Distribution

The habitat And distribution of Cyanobacteria is described below-

Aquatic Environments

Cyanobacteria are universal in their distribution from freshwater lakes and rivers and ponds to the oceans and seas. They are often found in quite dense numbers and fronds, especially in eutrophic conditions, where they are important components of the food chains and nutrient cycling.

Terrestrial Environments

In terrestrial ecosystems, cyanobacteria live in different types of soils, in the films on the rocks, or the arid desert. They participate in nitrogen fixation and act as nitrogen sources in the soil are frequently associated with fungi and contribute to the formation of lichens which are extremophiles.

Photosynthesis in Cyanobacteria

The photosynthetic process in Cyanobacteria is described below-

Light-Dependent Reactions

Light reactions in cyanobacteria take place at the sites of thylakoid membranes where chlorophyll will capture light energy to facilitate water molecule breakdown and liberation of oxygen, protons and electrons. This process creates ATP and NADPH required for the subsequent phases of the process of photosynthesis.

Light-Independent Reactions (Calvin Cycle)

ATP and NADPH that were formed during the light-dependent reactions are utilized in the Calvin cycle that takes place in the cytoplasm. In this cycle, carbon dioxide is converted into organic carbon and builds up glucose for energy food for the cyanobacteria.

Ecological and Environmental Significance

The ecological and environmental significance of Cyanobacteria are listed below-

Nitrogen Fixation

Mechanism of nitrogen fixation

Among other unique structures, plants have heterocysts where they perform nitrogen fixation hence making nitrogen available in the environment by breaking nitrogen gas (N₂) into ammonia (NH₃) through the nitrogenase enzyme.

Importance in nutrient cycling

Naturally occurring denitrification is a vital process in the remineralisation of necessary nutrients in ecosystems, and the input of these into plant systems, as well as the conservation of soil fertility, making it a key process in the nitrogen cycle in the environment.

Symbiotic Relationships

Lichens and plant associations

Cyanobacteria are in a mutualistic partnership with fungi which are found in lichens; the benefactors get carbohydrates from the cyanobacteria when they perform photosynthesis and they, in turn, get shelter and moisture. They also affiliate with plants such as the water fern known as Azolla which also benefits in nitrogen fixations in rice fields.

Symbiosis with other microorganisms

Cyanobacteria form mutualistic associations with other microorganisms to improve nutrient fluxes and the stability of both cyanobacteria and microorganisms.

Role In Aquatic Ecosystems

Primary producers

Primary producers include the cyanobacteria which engage in photosynthesis thus synthesizing organic compounds and oxygen used as the base of the consumers’ trophic level in the aquatic ecosystems.

Impact on water quality (eutrophication)

Over-enrichment of the water body by nutrients causes cyanobacteria to bloom in large numbers; their presence causes eutrophication which will deplete oxygen in the water, produce toxins and generally, deteriorate water quality which will hurt aquatic life and man.

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