Cyanobacteria

Play important role in aquatic environment_ nitrogen oxygen etc.

1. Cyanobacteria
Earlier called blue-green algae
Modern-day cyanobacteria include some 2000
species in 150 genera and 5 orders, with a great
variety of shapes and sizes.
Ecologically, there are three major groups of
cyanobacteria in the aquatic environment.

2. oCyanobacteria are photosynthetic prokaryotes
that capture sunlight for energy; use chlorophyll a
and various accessory pigments.
oCommon in lakes, ponds, springs, wetlands,
streams, and rivers.
oPlay a major role in the nitrogen, carbon, and
oxygen dynamics of many aquatic environments.
oMuch of their present diversity was achieved
more than 2 billion years ago

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

4. Cyanobacteria
• Cells small usually < 10μm,
• lacking nucleus, chloroplasts or other membrane bound
organelles, often with heterocysts or akinete spores.
• Blue green in colour due to a water soluble accessory
pigment (phycocyanin)
• Growth form as unicells, small clusters, filaments, or large
colonies
• photoautotrophs, aerobic
• Molecular evidence shows them to be the ancestors of
algal chloroplasts

5. Prokaryotes Eukaryotes

6. BOTANY

7. Cyanobacteria
Microscopic organisms
Found in marine sediments and pelagic zone,
freshwater lakes, soils,
Live in extreme environments –chemically and
temperature.
Ecologically, there are three major groups in the
aquatic environment: mat-forming species,
bloom-formers and picocyanobacteria

8. Importance
First organisms to have two photosystems
and to produce organic material and give off
O
2as a bi-product.
Very important to the evolution of the earths’
oxidizing atmosphere.

9. Importance
Many–fix or convert atmospheric
nitrogen into usable formsthrough
Nitrogen Fixation when other forms are
unavailable.
As atmospheric N
2is unavailable to
most living organisms because
breaking the triple bond is difficult, the
importance of cyanobacteria.
NN

10. Cyanobacteria Characteristics
-Pigments–chl a, phycobiliproteins
-phycoerythrin
-phycocyanin * Blue-GreenColor
-allophycocyanin
-Storage–glycogen
-Cell Walls–amino acids, sugars

11. Forms
•Unicell–with mucilaginous envelope
•Colonies–
•Filaments–uniserate in a single row
-OR -multiserate –not TRUE branching
when trichomes are > 1 in rows

12. Features
Trichome –row of cells
Mucilaginous sheath –
layer of mucilage outside of the cell wall.
}Filament

13. Features
Mucilaginous Sheath –
Function –protects cells from drying
and involved in gliding.
Sheath is often colored:
Red= acidic
Blue= basic
Yellow/Brown= high salt

14. Features
Heterocyst–thick walled cell, hollow
looking. Larger than vegetative cells.
FUNCTION –provides the anerobic
environment for N fixation.
H-heterocyst

15. Anabaena
Heterocyst
Vegetative cells

16. Habit –success due to ability tolerate a wide
range of conditions
•Marine –littoral and pelagic
•Fresh Water
•Hot Springs
•Terrestrial –soil flora

17. Heterocyst
•Larger than vegetative cells
•Hollow looking
•Thick walled –doesn’t allow atmospheric gas
to enter.
•Photosynthetically inactive
•No CO
2fixation or O
2evolution
•Formation of heterocysts triggered by
[molybdenum] and low [nitrogen]

18. Nitrogen
•Nitrogen is a limiting nutrient necessary
for the production of amino acids =
building blocks of life.

19. Nitrogen Fixation
•ONLY cyanobacteria and prokaryotic bacteria
can FIX nitrogen.
•Of these two only CYANOBACTERIA evolve
OXYGEN during photosynthesis
•Important because nitrogenase (enzyme
involved in fixing nitrogen) is INACTIVATED
by O
2.

20. Mechanisms to Separate
Nitrogenase from Oxygen
•Heterocyst (spatial)
OR
•Fix Nitrogen in the DARK but not LIGHT –
found in non-heterocystic cyanobacteria
(temporal)

21. AEROBIC
CO
2+ H
2O -----------CH
2O (sugar) +O
2
Electrons for PS1 come from PS2 which evolves
oxygen (splitting of water)
LIGHT

22. ANAEROBIC
in the presence of sulfur
2H
2S + CO
2--------CH
2O +2S + H
2O
H
2S is the electron donor –so the reaction does not
produce oxygen.

23. Advantage for Cyanobacteria
•Can live in fluctuating environments of
aerobic and anaerobic with light
present.

24. Cyano toxins in Cyanobacteria
•Neurotoxins –block neuron
transmission in muscles (Anabaena,
Oscillatoria)
•Hepatotoxins –inhibit protein
phosphatase, cause liver bleeding.
Found in drinking water. (Anabaena,
Oscillatoria, Nostoc)
Eg. swimmers itch -Lygnbia

25. Movement
•No flagellae or structures to enhance
movement
A)Excrete mucilage –jet propulsion, gliding
B)Helix –fibers send waves of contraction
Spirulina

26. Spirulina
•filamentous
•common in lakes with high pH
•major food for flamingo populations
•commercial food source

27. Anabaenawith a heterocyst
-common bloom forming species with nutrient loads

28. Lyngbia martensiana
Releases chemicals causing dermatitis

29. Asexual Reproduction
-Hormogonia formation -
-Endospore / Akinete formation -
-Fragmentation –
-Exospore

30. Asexual Reproduction
Hormogonia –short piece of trichome found in
filaments. It detaches from parent filament
and glides away
Hormogonia

31. Oscillatoriawith hormogonia
-short pieces of a trichome that become detached
from the parent filament and glide away to form
new filament.

32. Oscillatoria(filamentous) with hormogonia

33. Asexual Reproduction
Akinete–thick walled resting spore
A -akineteH

34. Akinete

35. Asexual Reproduction
Akinete–thick walled resting spore
Function –resistant to unfavorable
environmental conditions.
Appear as larger cells in the chain and
different than heterocyst. Generally lose
buoyancy
A -akineteH

36. Asexual Reproduction
Fragmentation-fragmentation

37. Stromatolites –Shark Bay, W. Australia
Cyanobacteria and Understanding the Past

38. Cyanobacteria photosynthesize using water as the
electron donor and produce oxygen as in algae.
A small number of strains can also use
hydrogen sulfide (H2S) and convert it to elemental
sulfur.
In general, cyanobacteria can tolerate low oxygen
conditions and concentrations of H2S that are toxic
to eukaryotic algae.
This tolerance may contribute to their ability to
survive in anoxic, eutrophic lake sediments as well
as in certain mat environments.