know about cyanobacteria
TRANSCRIPT
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