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Anabena: Occurrence

Anabena is a filamentous cyanobacteria that is known for its ability to fix nitrogen. It occurs in water as blooms and produces neurotoxins. Its structure includes strings of beaded cells called trichomes that contain heterocysts, specialized cells for nitrogen fixation. Anabena reproduces through hormogones, short filament fragments, and through akinetes, thick-walled resting cells, and can fix nitrogen through heterocysts that develop additional layers to prevent oxygen from inhibiting the nitrogen-fixing enzyme nitrogenase.

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21 views2 pages

Anabena: Occurrence

Anabena is a filamentous cyanobacteria that is known for its ability to fix nitrogen. It occurs in water as blooms and produces neurotoxins. Its structure includes strings of beaded cells called trichomes that contain heterocysts, specialized cells for nitrogen fixation. Anabena reproduces through hormogones, short filament fragments, and through akinetes, thick-walled resting cells, and can fix nitrogen through heterocysts that develop additional layers to prevent oxygen from inhibiting the nitrogen-fixing enzyme nitrogenase.

Uploaded by

Chshahzad Kamran
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Anabena

Occurrence
Filamentous cynobacteria

Known for nitrogen fixation

symbotic relations with mosquito ferns

some are endophytes;live in roots of cycas

found in water as blooms

produce neurotoxins (symbiotic)

DNA;7.5 million long base pairs

Natural fertilizers in paddy fields as convert nitrogen into ammonia

Structure
Filamentous bacteria like nostoc

Differentiate because of trichomes

Nostoc has mucilage and in form of colonies

Anabena has strings of beaded cells

Hetrocysts are presentin trichomes

Sheath are always hyaline and watery gelatinous


Structure of cell
Three layered inner:cellular,middle:pectic,outer:mucilage

Protoplast has two parts 1)chromoplast contain pigment2)colourless contain nucleus called as CENTRAL
BODY and CHROMATIN GRALULES

Herocycts are of same shape

Some organelles absent

Reproduction
Similar to nostoc.sexual reproduction absent

1)HORMOGONES FORMATION

Hormogones are short length filaments.develop large lenght by


vegetative reproduction.hormocysts are points from which hormogone break.

2)AKINETES FORMATION

Are formed during unfavorable conditions.are thick walled with large amount
of food materials.there walls is two or three layered thick.have granular protoplast.can form
filaments.can survive in severe conditions

3)ENDOSPORE FORMATION

Are rare in anabena

Nitrogen fixation in anabena

It occurs in time of low environmental nitrogen.one cell out of ten differentiate into hetrocysts.it supply
with nitrogen.in return get products of photosynthesis.they cannot perform photosynthesis.enzyme in
hetrocyst is NITROGENASE.it is unstable in oxygen presence.it is kept isolated from oxygen.to maintain
low level of oxygen they develop three additional layers outside the cell.it prevent enterence of
oxygen.it give enlarge and round appearance.due to this rate of diffusion of hetrocysts is low than
vegetative cells.one layer create layer of polysacrides.nitrogen is fixed in this oxygen resistance
layer.photosystem is also eliminated to prevent it from oxygen.

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