Cyanobacteria an oldest living organelles on Earth

1. Prepared by:
Dr.E.Gayathiri
Department of Plant Biology and Plant Biotechnology
Guru Nanak College,Chennai.

2. INTRODUCTION
 HABITAT
 Evolution (Cyanobacteria are the first algae!!)
 Structure
 Pigments
 Endosymbiosis

3. Cyanobacteria terminology
 Division Cyanophyta
 Cyanobacteria ‘formerly known as’ Blue Green Algae -
Cyano = blue
 Bacteria – acknowledges that they are more closely
related to prokaryotic bacteria than eukaryotic algae

4. Habitat
 Found in the oceans and seas, fresh water , rocks.
 Occur ad planktonic cell
 Form phototrophic biofilm
 Present in damp soil and even in temporarily
moistened rocks
 Some species of cyanobacteria coexist with fungi to
form lichens.
 Endosymbiont in Bryophytes, some plants ,many
protists etc…

5. Cyanobacteria have played an important role in the
development of Earth.
Scientists believe that they were the first photosynthetic
organisms to occur on Earth’s surface.
Beginning about 2.7 billion years ago, the oxygen
produced by cyanobacteria enriched Earth’s atmosphere
and converted it to its modern form.
This conversion made possible all life forms that use
oxygen for cellular respiration
The Chemical basis of life.

6. Nitrogen Fixing Cyanobacteria
 They can be Unicellular, Filamentous or they could be
colonial.
 Some Cyanobacteria can fix nitrogen
 Nitrogen fixing requires nitrogenase enzyme, which works
under anaerobic condition
 Nitrogen fixation takes place in special cell, Heterocyst.
Eg: Nostoc
 Eg: Oscilatoria (without Heterocyst)

7. Structure of Cyanobacteria
 Cell wall- Multilayered
Peptidoglycan
 Gelatinous later on the
otter cell wall
 Inner to cell is
cytoplasm
 Cytoplasm is divided
into two zone
 Otter zone have
membranous structure
called thylakoids
 Inner zone is endoplasm
with circular DNA or
Nucleiod
Source: Biology boom

8. Pigments
 Chlorophyll- A, Xanthophyll,
 Phycobilin,
 Carotenids

9. Inner cytoplasm (Endoplasm)
 No pigment
 Absence of Flagella
 Ribosomes are present
 As all Prokaryotes
absence of organelles:-
• Nucleus
• Chloroplasts
• Mitochondria
• Golgi bodies
(dictyosomes)
• Endoplasmatic reticulum
(ER)

10. Endosymbiosis