Poisonous Plants, Fungi, and Algae

1. Poisonous Plants, Fungi, and Algae III - Algal Toxins

2. Kingdom Monera • Cyanobacteria- blue green algae • Used as a food source: Nostoc, Spirulina (since ancient times - today protein additive) • Toxins produced by several species can cause problems during blooms

3. Nostoc Oscillatoria

4. Kingdom Protista • Six divisions of algae: • Division Pyrrophyta - dinoflagellates • Division Chrysophyta - diatoms • Division Euglenophyta - euglenoids • Division Chlorophyta - green algae • Division Rhodophyta - red algae • Division Phaeophyta - brown algae

5. Dinoflagellates • Unicellular algae covered with cellulose plates giving an armored appearance • Important to the food chain in marine and fresh water • Some marine species cause Red Tides • Bloom conditions • Color the water “red” • Produce powerful toxins • Pfiesteria newly recognized problem

6. Dinoflagellates

7. Algal Blooms and Harmful Algal Blooms

8. Toxic Cyanobacteria • Normally algal cells only release the toxins when the cells die or when they age and become leaky • Poisoning typically occurs when animals ingest whole cells • If water is treated to break up a bloom, it is possible for fatal levels of the toxin to be released • 12 genera of cyanobacteria known to be toxin-producers. • Two of the most toxic - Anabaena and Microcystis.

9. Types of toxins • Two groups of toxins in the cyanobacteria • Neurotoxins - alkaloids - nervous systems • Saxitoxins • Anatoxins - Very fast death factor • Hepatotoxins - cyclopeptides - target the liver • Microcystins • Nodularin

10. Anabaena • Anabaena - a genus of filamentous N2-fixing cyanobacteria • Known for producing a suite of cyanotoxins which range from the neurotoxic anatoxins and saxitoxins to the hepatotoxic microcystins. • Genus can be found throughout the world

11. Anabaena

12. Microcystis • Microcystis spp. are single-celled, colonial, freshwater cyanobacteria • World-wide distribution • Microcystins (hepatotoxins) are main toxin type • M. aeruginosa and M. viridis appear to be the most common microcystin-prodcuing species.

13. Microcystis

14. Anatoxins • Neurotoxic alkaloids produced by a number of cyanobacterial genera including Anabaena, Oscillatoria and Aphanizomenon • Anatoxin – a: one of the most toxic of this group, can be lethal within 4 minutes after ingestion, depending on the quantity • This led to the compound being dubbed "Very Fast Death Factor."

15. Anatoxin-a

16. Anatoxins • Affects nervous system, often causing death due to paralysis of the respiratory muscles • Acetylcholine mimic - irreversibly binds the nicotinic acetylcholine receptor (NAChR) • Na+ channel locked open, and the muscles become over-stimulated, fatigued and then paralyzed. • When respiratory muscles become affected, convulsions occur due to a lack of oxygen in brain • Suffocation the final result a few minutes after ingestion of the toxin

17. Saxitoxins • Neurotoxic alkaloids produced by both marine and freshwater algae • In freshwater, blue-green algae, especially Anabaena circinalis, manufacture the toxins and may transfer them to freshwater shellfish or just poison the water • In the oceans, dinoflagellates, especially Alexandrium spp, produce saxitoxins which are accumulated by mollusks feeding upon them

18. General Structure of Saxitoxin

19. Saxitoxins • Bind to and block the sodium channel on neurons, inhibiting the passage of Na+ • Causes muscles to relax and may lead to respiratory failure • Victims experience tingling and numbness of the mouth, tongue, face and extremities • Nausea and vomiting may accompany the above symptoms. • In severe cases, patients will exhibit advanced neurological dysfunction and paralysis

20. Hepatotoxins • More widespread and have caused problems throughout the world • Cyclopeptides - Microcystins have 7 amino acids while Nodularins have 5 amino acids • Specifically target liver cells where they inhibit protein phosphatases - in liver cells these are involved in maintenance of the cytoskeleton

21. Microcystin

22. Hepatotoxins • Act on the cytoskeleton within the liver cells causing cytoskeleton to collapse because the balance of phosphate groups on the cytoskeletal proteins is disrupted - liver cells collapse • Can be fatal by causing blood to pool in the liver • Increase tumor development and may be responsible for the high rates of liver cancer in parts of China where blooms frequently occur. • Used in research to understand the basic functioning of the cytoskeleton

23. Other Toxins • Less deadly toxins are responsible for conditions such as "swimmer's itch" • Toxins of several marine cyanobacteria cause this form of contact dermatitis characterized by swelling and inflammation of mucus membranes and redness of the skin

24. Dinoflagellates and Red Tides • Several species of dinoflagellates, especially Gymnodinium breve, Alexandrium spp, produce powerful toxins that can cause massive fish kills • As schools of fish swim through a bloom, the dinoflagellates may be disrupted or killed, releasing neurotoxins into the water • The toxins damage the gills or suppress heart rate and result in asphyxiation - hundred or thousands of dead fish wash up on beaches

25. Other Problems • In other instances, the toxins accumulate in various filter feeding shellfish • When the shellfish are eaten the toxins can affect humans • Cause various syndromes depending on the dinoflagellate and type of toxin

26. Dinoflagellate Poisonings • Paralytic Shellfish Poisoning (PSP) • Diarrhetic Shellfish Poisoning (DSP) • Neurotoxic Shellfish Poisoning (NSP) • Ciguatera Fish Poisoning (CFP) • Pfiesteria piscicida

27. Paralytic Shellfish Poisoning - PSP • Dinoflagellates - Alexandrium spp, Gymnodinium spp, and Pyrodinium spp • Toxins involved - saxitoxins • As already described for cyanobacteria - can cause death due to respiratory arrest

28. Neurotoxic Shellfish Poisoning • Dinoflagellate - Gymnodinium breve • Toxin - Brevetoxins • Large lipophilic polyether toxins • Gastrointestinal and neurological symptoms • Causes fish kills but usually not deadly for people • Aerosol exposure from sea spray has resulted in respiratory problems in humans

29. Brevetoxin

30. Ciguatera Fish Poisoning - CFP • Dinoflagellates - Gambierdiscus toxicus • Toxins - ciguatoxin and maitotoxin • Produce gastrointestinal, neurological and cardiovascular symptoms from eating contaminated fish • Toxins isolated from the flesh and viscera of various tropical and subtropical fish • Paralysis and death have occurred but usually symptoms are less severe

31. Ciguatoxin

32. Ciguatoxin • Fish are unaffected • People eating contaminated fish experience nausea, vomiting, and diarrhea and develop bizarre neurological symptoms that can be long-lasting • Cardiac - arrhythmias and low blood pressure • Dizziness, muscular weakness, reverse sensations such as hot objects feeling cold to the touch

33. Pfiesteria piscicida • Pfiesteria piscicida implicated as the organism responsible for recent fish kills and fish disease • Since the early 1990s toxins produced by Pfiesteria may have killed over one billion fish in North Carolina alone with other outbreaks along east coast • Toxins not identified yet • People exposed to toxins have developed skin and neurological problems

34. Pfiesteria • Complex life cycle • Appears to be around 24 different stages in the life cycle – with flagellated, amoeboid, and encysted stages • Only 3 stages appear to form toxins

35. Pfiesteria • Normally feed on bacteria and algae but able to produce toxins • Toxins stun fish and injure the fish skin causing them to lose the ability to maintain their internal osmotic balance • Skin destroyed, bleeding sore develop, hemorrhaging, death • When the fish become incapacitated, Pfiesteria piscicida feed on the epidermal cells, blood, and other fluids • Pfiesteriaappears to release the toxins to immobilize fish and then feed off the fish- dinoflagellates responsible for other Red Tides release their toxins only when the cells die and break apart

36. Pfiesteria • Toxin not identified yet • When Pfiesteria cells were injected subcutaneously into rats, they showed persistent learning impairments • Studies have identified the neurotransmitter receptor that is the likely target for these still unidentified toxins – N-methyl-D-aspartate receptor – rat brain receptor involved in cognitive function • Second species Pfiesteria shumwayae appears to cause more lethal effects among fish • 2002 paper cast doubts on existence of toxin with fish kills due to another mechanism