Cyanobacteria, often referred to as blue-green algae, are prokaryotic microorganisms that photosynthesize and can thrive in diverse environments. They have a primitive cell structure with a two-layered cell wall and a protoplast containing pigments like phycocyanin and chlorophyll. Specialized cells, such as akinetes and heterocysts, help them survive unfavorable conditions and fix nitrogen.

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Cyanobacteria
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Volvox sp.

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• Cyanobacteria ‘known as’ BlueGreen Algae
• Cyano = blue
• Bacteria = they are more closely related to prokaryotic bacteria (No Nucleus) than
eukaryotic algae
• Microscopic organisms
• Gets energy through photosynthesis and chemosynthesis
• Cyanobacteria can be found in almost every environment, from oceans to fresh
water to bare rock to soil
Characteristics

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Phycocyanin : BlueGreen Color
Chlorophyll : Green Color
Others : Phycoerythrin, Xanthophyll
Pigment

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Forms
Unicell Colonies Filaments

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Cell structure
The cell structure is very primitive
Each cell is composed of two parts:
a)cell wall
b)protoplast
The cell wall is composed of 2 layers:
1. The inner layer of which is thin and firm
composed of peptidoglycan.
2. The outer layer of the wall is thicker and
gelatinous known as the sheath and mainly
constituted of pectic compounds.

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Cell structure
The protoplast consists of 2 parts:
1. peripheral pigmented (coloured) region
surrounding a colourless central region. It
contains the blue pigment phycocyanin
together with chlorophyll and known as
chromoplasm
2. The colourless inner region (central body)
contains several chromatin granules (DNA)
which represent a primitive type of nucleus
that lacks nuclear membrane and organells
Chromoplast
Cell wall
Central body

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Modified cell
Cells with resistant spores : akinetes – resistant to unfavorable
environmental conditions
Thick walled cells for fixing nitrogen : heterocysts – provides the
anerobic environment for N fixation

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