know about cyanobacteria

Although called blue-green algae

earlier, since it is prokaryotic in cell

structure and ‘cyano’ refers to the

colour blue-green, the present name

represents its many species.

*

*Cyanobacteria (also referred to as blue-green algae) cause a multitude

of water-quality concerns, including the potential to produce toxins and

taste-and-odor compounds.

Toxins and taste-and-odor compounds may cause significant economic

and public health concerns, and are of particular interest in lakes,

reservoirs, and rivers that are used for drinking-water supply, recreation,

or aquaculture.

Cyanobacteria is bacteria with a prokaryotic cell structure and

containing chlorophyll-a (a photo-pigment characteristic of eukaryotic

algae and higher plants).

- 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

*

Prokaryotes Eukaryotes

BOTANY

-Microscopic organisms

- Found in marine sediments and pelagic zone,

freshwater lakes, soils,

- Live in extreme environments – chemically and

temperature.

*

*

1) First organisms to have 2 photosystems and to produce organic material and give off O2 as a bi-product.

Very important to the evolution of the earths’ oxidizing atmosphere .

*2) Many – fix or convert atmospheric nitrogen into

usable forms through Nitrogen Fixation when other

forms are unavailable.

IMPORTANT because atmospheric N2 is unavailable to

most living organisms because breaking the triple

bond is difficult

N N

- Pigments – chl a, phycobiliproteins

- phycoerythrin

- phycocyanin * Blue-Green Color

- allophycocyanin

- Storage – glycogen

- Cell Walls – amino acids, sugars

*

*

*Unicell – with mucilaginous envelope

*Colonies –

*Filaments – uniserate in a single row

- OR - multiserate – not TRUE branching

- when trichomes are > 1 in rows

Trichome – row of cells

*

Mucilaginous sheath –

layer of mucilage outside of the cell wall.

} Filament

Mucilaginous Sheath –

Function – protects cells from drying and

involved in gliding.

Sheath is often colored:

Red = acidic

Blue = basic

Yellow/Brown = high salt

*

Heterocyst – thick walled cell, hollow looking.

Larger than vegetative cells.

FUNCTION – provides the anerobic environment

for N fixation.

*

H- heterocyst

Anabaena

Heterocyst

Vegetative cells

*

*Marine – littoral and pelagic

*Fresh Water

*Hot Springs

*Terrestrial – soil flora

**Larger than vegetative cells

*Hollow looking

*Thick walled – doesn’t allow atmospheric gas to enter.

*Photosynthetically inactive

*No CO2 fixation or O2 evolution

*Formation of heterocysts triggered by [molybdenum] and

low [nitrogen]

*

*Nitrogen is a limiting nutrient necessary

for the production of amino acids =

building blocks of life.

*

*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 O2.

*

*Heterocyst (spatial)

OR

*Fix Nitrogen in the DARK but not LIGHT –

found in non-heterocyst cyanobacteria

(temporal)

*

CO2 + H2O ----------- CH2O (sugar) +O2

Electrons for PS1 come from PS2 which evolves oxygen

(splitting of water)

LIGHT

*

2H2S + CO2 -------- CH2O +2S + H2O

H2S is the electron donor – so the reaction does not produce

oxygen.

*

*Can live in fluctuating environments of

aerobic and anaerobic with light present.

*

*Neurotoxins – block neuron transmission in muscles (Anabaena, Oscillatoria)

*Hepatotoxins – inhibit protein phosphatase, cause liver bleeding. Found in drinking water. (Anabaena, Oscillatoria, Nostoc)

E. g. swimmers itch - Lygnbia

*

* No flagellae or structures to enhance movement

A) Excrete mucilage – jet propulsion, gliding

B) Helix – fibers send waves of contraction

Spirulina

Spirulina

• filamentous

• common in lakes with high pH

• major food for flamingo populations

• commercial food source

Anabaena with a heterocyst

- common bloom forming species with nutrient loads

Lyngbia martensiana

Releases chemicals causing dermatitis

*

- Hormogonia formation -

- Endospore / Akinete formation -

- Fragmentation –

- Exospore

*

Hormogonia – short piece of trichome found in

filaments. It detaches from parent filament and glides

away

Hormogonia

Oscillatoria with hormogonia

- short pieces of a trichome that become

detached from the parent filament and glide

away to form new filament.

Oscillatoria (filamentous) with hormogonia

*

Akinete – thick walled resting spore

A - akinete H

Akinete

*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 - akinete H

*Fragmentation - fragmentation

*

*3.5by old carbonaceous microfossils S.Africa

*3.4by old filaments and microbial fossils – W. Australia

*3.4 by old stromatolites – S.Africa, Australia

Stromatolites – Shark Bay, W. Australia

Cyanobacteria and Understanding the Past