cyanobacteria lecture

Cyanobacteria

THE FIRST ALGAE!!!!!

Evolution• Old 3.5 billion years• Dominated as biogenic reefs• During Proterozoic – Age of Bacteria

(2.5 bya – 750 mya) they were wide spread

• Then multicellularity took over• Cyanobacteria were first algae!

Cyanobacteria terminology

- Division Cyanophyta

- Cyanobacteria ‘formerly known as’ BlueGreen Algae

- Cyano = blue

- Bacteria – acknowledges that they are more closely related to prokaryotic bacteria than eukaryotic algae

Bac

teri

a

Arc

heae

Other Eukaryotes Ani

mal

iaF

ungi

Gre

en P

lant

sR

ed A

lgae

Prokaryotes Eukaryotes

Cya

noba

cter

iaA

rche

ae

Bro

wn

Alg

ae

Fun

gi

Gre

en P

lant

sR

ed A

lgae

BOTANYD

iato

ms

Cyanobacteria

-Microscopic organisms

- Found in marine sediments and pelagic zone, freshwater lakes, soils,

- Live in extreme environments – chemically and temperature.

Importance

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 .

!!!

Importance2) 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

Cyanobacteria Characteristics

- Pigments – chl a, phycobiliproteins

- phycoerythrin

- phycocyanin * BlueGreen Color

- allophycocyanin

- Storage – glycogen

- Cell Walls – amino acids, sugars

Forms

• Unicell – with mucilaginous envelope

• Colonies –

• Filaments – uniserate in a single row

- OR - multiserate – not TRUE branching when trichomes are > 1 in rows

FeaturesTrichome – row of cells

Mucilaginous sheath –

layer of mucilage outside of the cell wall.

} Filament

FeaturesMucilaginous Sheath –

Function – protects cells from drying and involved in gliding.

Sheath is often colored:

Red = acidic

Blue = basic

Yellow/Brown = high salt

FeaturesHeterocyst – thick walled cell, hollow looking. Larger than vegetative cells.

FUNCTION – provides the anerobic environment for N fixation.

H- heterocyst

Anabaena

Heterocyst

Vegetative cells

Habit – success due to ability tolerate a wide range of conditions

• Marine – littoral and pelagic

• Fresh Water

• Hot Springs

• Terrestrial – soil flora

Heterocyst• 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 and low [nitrogen]

Nitrogen

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

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 O2.

Mechanisms to Separate Nitrogenase from Oxygen

• Heterocyst (spatial)

OR

• Fix Nitrogen in the DARK but not LIGHT – found in non-heterocystic cyanobacteria (temporal)

AEROBIC

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

Electrons for PS1 come from PS2 which evolves oxygen (splitting of water)

LIGHT

ANAEROBIC in the presence of sulfer

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

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

Advantage for Cyanobacteria

• Can live in fluctuating environments of aerobic and anaerobic with light present.

Cyanotoxins 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

Movement

• 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

Asexual Reproduction

- Hormogonia formation -

- Endospore / Akinete formation -

- Fragmentation –

- Exospore

Asexual ReproductionHormogonia – 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

Asexual ReproductionAkinete – thick walled resting spore

A - akineteH

Akinete

Asexual ReproductionAkinete – 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

Asexual ReproductionFragmentation - fragmentation

Oldest Fossils• 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