Cyanobacteria - Cell Structure

Description:

Cyanobacteria are unicellular, colonial or they may be filamentous. Each filament consists of a sheath of mucilage and one or more cellular strands called trichomes. Flagella is absent in cyanobacteria but gliding movements are known in a number of cyanobacteria. They are much larger and more elaborate than bacteria. They possess peptidoglycan cell wall, naked DNA, 70S ribosomes and membrane bound structures are absent.

Cell Wall

• Four layered.
• Peptidoglycan present in the second layer.
• The outer part of protoplast contains a number of photosynthetic thylakoids or chromatophores. It is called chromoplasm.

Thylakoids

• The thylakoids lie freely in cytoplasm.
• Their membranes contain chlorophyll a, carotenes and xanthophylls.
• Chlorophyll b is absent.
• Phycobilisomes are small granules that are attached to the thylakoid membranes.