1. CYANOBACTERIA PIGMENTATIONS AND TOXINS Lect 5

2. Cyanobacteria Pigmentation  Pigments are chemical compounds which reflect only certain wavelengths of visible light  In plant, algae, and cyanobacteria, pigments are the means by which the energy of sunlight is captured for photosynthesis. However, since each pigment reacts with only a narrow range of the spectrum, there is usually a need to produce several kinds of pigments, each of a different color, to capture more of the sun's energy.

3. Three Basic Classes of Pigments. Three major classes of photosynthetic pigments occur among the algae are:  Chlorophylls  carotenoids (carotenes and xanthophylls)  Phycobilins

4. Basic Classes of Pigments  Chlorophylls and carotenes are generally fat soluble molecules and can be extracted from thylakoid membranes with organic solvents such as acetone, methanol or DMSO.  The phycobilins in contrast, are water soluble and can be extracted from algal tissues after the organic solvent extraction of chlorophyll in those tissues.

5. Basic Classes of Pigments  Chlorophylls: are greenish pigments and it captures the energy of sunlight to provide energized electrons to other molecules during photosynthesis process.  All plants, algae, and cyanobacteria which photosynthesize contain chlorophyll "a”. This is the molecule which makes photosynthesis possible  Carotenoids: are usually red, orange, or yellow pigments. Carotenoids cannot transfer sunlight energy directly to the photosynthetic pathway, but must pass their absorbed energy to chlorophyll. For this reason, they are called accessory pigments

6. Basic Classes of Pigments  Phycobilins: are water-soluble pigments, and are therefore found in the cytoplasm, or in the stroma of the chloroplast. They occur only in cyanobacteria and rhodophyta.  The bluish pigment phycocyanin, gives the Cyanobacteria their name. The reddish pigment phycoerythrin, gives the red algae their common name.

7. Pigment composition of several algal groups DIVISIONCOMMON NAMEMAJOR ACCESSORY PIGMENT ChlorophytaGreen algaechlorophyll b CharophytaCharophyteschlorophyll b EuglenophytaEuglenoidschlorophyll b PhaeophytaBrown algae chlorophyll c1 + c2, fucoxanthin Chrysophyta Yellow-brown or golden- brown algae chlorophyll c1 + c2, fucoxanthin Pyrrhophyta Dinoflagellateschlorophyll c2, peridinin CryptophytaCryptomonads chlorophyll c2, phycobilins RhodophytaRed algae phycoerythrin, phycocyanin CyanophytaBlue-green algae phycocyanin, phycoerythrin

8. Cyanotoxins  Cyanotoxins: are toxins produced by bacteria called cyanobacteria (also known as blue-green algae). Cyanobacteria are found almost everywhere, but particularly in lakes and in the ocean where, under certain conditions, they reproduce exponentially to form blooms. Blooming cyanobacteria can produce cyanotoxins in such concentrations that they poison and even kill animals and humans. Cyanotoxins can also accumulate in other animals such as fish and shellfish, and cause poisonings such as shellfis poisoning.

9. Harmful Algal Blooms (HABs)  Cyanotoxins are often implicated in what are commonly called red tides or harmful algal blooms. Lakes and oceans contain many single-celled organisms called phytoplankton. Under certain conditions, particularly when nutrient concentrations are high, these organisms reproduce exponentially. The resulting dense swarm of phytoplankton is called an algal bloom.

10. Harmful Algal Blooms (HABs  Cyanobacteria also commonly produce blooms and HABs. Cyanobacteria species are often toxic, and in freshwater ecosystems are the most common cause of eutrophication. Their blooms can look like foam, scum or mats or like paint floating on the surface of the water, but they are not always visible. Nor are the blooms always green; they can be blue, and some cyanobacteria species are coloured brownish- red.

11. Red Tide  The term "red tide" is often used in the United States of America to describe a particular type of algal bloom common to the eastern Gulf of Mexico, also called the "Florida red tide". This type of bloom is caused by a species of dinoflagellate known as Karenia brevis, and these blooms occur almost annually along Florida waters. The density of these organisms during a bloom can exceed tens of millions of cells per litre of seawater, and often discolor the water a deep reddish- brown hue.  Red tides are caused by increase in nutrients that algae need, usually due to farm runoff, causing an overpopulation

12. Microcystins  Microcystins: named after the first organism discovered to produce them, Microcystis aeruginosa. They can be produced during a bloom and they are a problem worldwide in freshwater ecosystems.  They bioaccumulate in the liver of fish and in the mussels.  They are hepatotoxic and can cause serious damage to the liver in humans.

13. Nodularins  Nodularins: produced by the cyanobacterium Nodularia spumigena  This cyanobacterium blooms in water bodies throughout the world.  Nodularins are potent hepatotoxins and can cause serious damage to the liver.  They present health risks for wild and domestic animals as well as humans, and in many areas pose major challenges for the provision of safe drinking water.

14. Anatoxin  Anatoxin: also known as "Very Fast Death Factor“(VFDF), began in 1961 following the deaths of cows that drank from a lake containing an algal bloom in Saskatchewan, Canada.  The toxin is produced by at least four different genera of cyanobacteria  it acts directly on the nerve cells (neurons) as a neurotoxin and the nerve tissues which communicate with muscles. the communication between the brain and the muscles is disrupted and breathing stops.

15. Cylindrospermopsins  Cylindrospermopsins: was first discovered after an outbreak of a mystery disease on Palm Island in Australia and it produced by a bloom of Cylindrospermopsis raciborskii in the local drinking water supply  Cylindrospermopsin is toxic to liver and kidney tissue.  Toxic blooms of genera which produce cylindrospermopsin are most commonly found in tropical, subtropical and arid zone water bodies, and have recently been found in Australia, Europe, Israel, Japan and the USA.

16. Saxitoxins  Saxitoxins: Saxitoxin (STX) is one of the most potent natural neurotoxins known.  Saxitoxin is produced by the cyanobacteria Anabaena spp., some Aphanizomenon sp., Cylindrospermopsis sp., Lyngbya sp and some marine dinoflagellates.  Saxitoxins bioaccumulate in shellfish.  It acts on the voltage-gated sodium channels of nerve cells, preventing normal cellular function and leading to paralysis  Death often occurs from respiratory failure

17. Cyanotoxin Primary target organ in mammals Cyanobacteria genera Microcystins Liver MicrocystisMicrocystis, Anabaena, Planktothrix (Oscillatoria), Nostoc, Hapalosiphon, AnabaenopsisAnabaenaPlanktothrixNostocHapalosiphon Anabaenopsis NodularinsLiverNodularia Anatoxin-a(S)Nerve synapseAnabaena AplysiatoxinsSkin LyngbyaLyngbya, Schizothrix, Planktothrix (Oscillatoria)SchizothrixPlanktothrix CylindrospermopsinsLiverCylindrospermopsisCylindrospermopsis, Aphanizomenon, UmezakiaAphanizomenonUmezakia Lyngbyatoxin-a Skin, gastro- intestinal tract Lyngbya SaxitoxinNerve axons AnabaenaAnabaena, Aphanizomenon, Lyngbya, CylindrospermopsisAphanizomenonLyngbya Cylindrospermopsis