Anabaena is a genus of nitrogen-fixing cyanobacteria that forms a symbiotic relationship with the aquatic fern Azolla. Anabaena azollae lives within the leaves of Azolla, where it differentiates specialized cells called heterocysts that fix atmospheric nitrogen. In exchange, the cyanobacteria receives carbon compounds from the fern. This mutually beneficial relationship allows Azolla plants inoculated with Anabaena to double their biomass within a few days. Farmers have used the Azolla-Anabaena symbiosis for centuries to naturally fertilize rice paddies, providing rice crops with 50-75% of their nitrogen needs and increasing yields by over 150% in some cases.

1. UNIVERSITY OF AGRICULTURAL SCIENCES
GKVK BENGALURU-65
COMMERICAL PRODUCTION OF
BIO-FERTILIZERS
CMA-404(0+5)
TOPIC : Symbiosis in Anabaena azolla
PRESENTING BY:
Guruprasad A
ALB4o54

2. Anabaena
● Anabaena is a genus of filamentous cyanobacteria
that exists as plankton.
● They form symbiotic relationship with certain plants
and fix nitrogen.
● The Genes was identified by Bory de Saint Vincent
and Flahault in 1886

3. HISTORY
● A DNA sequencing project was undertaken in 1999, and
mapped the complete genome of Anabaena, which is 7.2
million base pairs long.
● The study focused on heterocysts, which converts nitrogen
into ammonia.
● Certain species of Anabaena have been used in paddy
fields proving to be an effective natural fertilizer.

4. Anabaena as observed in
microscope

5. SCIENTIFIC CLASSIFICATION OF
Anabaena spp
❑KINGDOM : Bacteria
❑PHYLUM : Cyanobacteria
❑CLASS : Hormogoneae
❑ORDER : Nostocales
❑FAMILY : Nostocaceae
❑GENUS : Anabaena

6. COMMON SPECIES

7. AZOLLA:
● Azolla is a genus of common water fern whose small leaves
accumulate on the surface of bodies of water creating mats.
● Azolla is also known as mosquito fern or duck weed fern of fairy
moss.
● Azolla is highly productive plant it doubles its biomass in 3 to 10
days.
● Azolla is used as an organic biofertilizer to increase the nitrogen
levels in paddy.
● The rotting plant material releases nitrogen to the rice plants
providing upto 9 tonnes of protein/ha/year.

8. SCIENTIFIC CLASSIFICATION OF Azolla
fern
●Kingdom : Plantae
●Division : Pteridophyta
●Class : Polypodiopsida
●Order : Salviniales
●Family : Salviniaceae
●Genus : Azolla

9. AZOLLA

10. About Anabaena azollae:
● It is a small filamentous phototrophic cyanobacteria generally
seen as a multicelluar organisms with two distinct
interdependent cell types.
● The first cell type is a small circular photoautotrophic
vegetative cell that performs oxygenic photosynthesis and is
typically blue-green in colour.
● The second is the heterocyst a larger paler more
homogeneous cell produced by Anabaena to fix atmospheric
nitrogen.
● Anabaena azollae is usually found within ovoid cavities
inside the leaves of water fern Azolla.

11. Two types of cells,
1. Vegetative cells
2. Heterocyst

12. ECOLOGY OF Anabaena azollae
● Anabaena azollae and Azolla have formed a symbiotic
relationship in which the cyanobacterium receives carbon and
nitrogen sources from the plant in exchange for fixed nitrogen.
● Anabaena azollae are usually found within ovoid cavities
located within the plants dorsal leaves and are connected to
the external environment by pores.
● Epidermal cells inside the leaf cavities of Azolla project inwards
forming numerous multicellular hairs wit wart like outgrowths.
● These hairs are thought to serve as a pathway for the free
exchange of nutrients between Anabaena azollae and Azolla.

13. Anabaena present in leaf cavities of
Azolla

14. ● When free living Anabaena azollae develops only
5 to 10% of its cells into heterocyst . But when
living in conjunction with Azolla it increases its
heterocyst production upto 25 to 30%.
• Anabaena azollae is able to fix nitrogen so
efficiently that population of Azolla have been
known to double their biomass every two to three
days.

15. Nitrogen fixation
● Nitrogen fixation is a remarkable prokaryotic skill in which
inert atmospheric nitrogen gas (N2) is combined with
hydrogen to form ammonia (NH3).
● This vital process along with nitrification (formation of nitrites
and nitrates) and ammonification (formation of ammonia
from protein decay) make nitrogen available to autotrophic
plants and ultimately to all members of the ecosystem.
● Although Azolla can absorb nitrates from the water, it can
also absorb ammonia secreted by Anabaena within the leaf
cavities

16. Mechanism
● Under nitrogen-limiting conditions, vegetative cells
differentiate into heterocysts at semi-regular intervals along the
filaments.
● Heterocysts are cells that are terminally specialized for
nitrogen fixation.
● The interior of these cells is microoxic as a result of increased
respiration, inactivation of O2 producing photosystem (PS) II,
and formation of a thickened envelope outside of the cell wall.

17. ● Nitrogenase, sequestered within these cells, transforms
dinitrogen into ammonium at the expense of ATP and
reductant—both generated by carbohydrate metabolism, a
process that is supplemented, in the light, by the activity of
PS I.
● Carbohydrate, probably in the form of sucrose, is
synthesized in vegetative cells and moves into
heterocysts.
● In return, nitrogen fixed in heterocysts moves into the
vegetative cells, at least in part in the form of amino acids

18. Energy demand in Nitrogen fixation
Two molecules of ammonia are produced from one molecule of nitrogen
gas. The reaction requires 16 molecules of ATP and a supply of electrons
and protons (hydrogen ions) plus the enzyme nitrogenase.

19. Symbiotic N2-fixation: Azolla - Anabena

20. IMPORTANCE OF Anabaena azollae
● For centuries the symbiotic relationship between Anabaena azollae
and Azolla has benefitted farmers across world.
● It is commonly used as green manure which increases rice production.
● It is either incorporated as green manure at the beginning of the
cropping season or grown as dual crop along with rice crop.
● Azolla can also provide aerobic transformations such as metane
oxidation through enhance aeration of flood water in rice field.
.

21. ● The fern is responsible for providing 50 to 75% of
the nitrogen required by the rice crop.
● According to some reports Azolla has helped
increase rice yields as much as 158% per year.
● Azolla is also used in fish food and garden mulch.
● It is a natural food for various types of insects.
● It is also used as water purifier and for control of
weeds and mosquitoes.

22. Rice-Azolla-Fish, China
Azolla to feed cows,
Thailand
Rice-Azolla-Ducks, Korea
Takao Furuno
Symbiotic N2-fixation: Azolla - Anabena

23. AZOLLA FERTILIZED IN PADDY
FIELDS

24. Thank you