King Saud University College of Science

Microbiology Department

By: Abdelrahman A. Dawoud Yasser Al HajajFaisal l Mutairy

Mohammed Ansari

Prof. Ibraheem IBM

Cyanobacterial Toxins

Cyanobacteria ~ blue-green algae

• Ancient, ubiquitous• Created world’s oxygen atmosphere• Ancestors of green plants• Produce ~ 50% of the oxygen in theatmosphere todayBUT:• Develop excessive blooms, scums, matsdue to human pressures on waterresources• Present economic, aesthetic, and healthproblems• Many produce potent TOXINS• Risk management needs

Freshwater cyanobacterial blooms, a global

phenomenon

Cyanotoxins

•occur annually in waterresources, including thoseused for drinking, fisheries,recreation and tourism

•present substantial risks tohuman and animal health

•are produced globally •require to be detected

andquantified to meet guidelinesand regulations

Classes of Cyanotoxins

(1 )Hepatotoxins: microcystins, nodularinscylindrospermopsins

(2 )Neurotoxins: anatoxin-a, homoanatoxinanatoxin-a(s), saxitoxins

(3 )Irritants and allergenic toxins: aplysiatoxins,lipopolysaccharide endotoxins

Microcystins •Group of >80

structurally relatedcyclic heptapeptides

•In acute cases deathoccurs byhypovolaemic shock

•Able to inhibit proteinphosphatases andmay affect cell cycle

•Tumour promoters

Cylindrospermopsin •A guanidine alkaloid

hepatotoxin andgenotoxin

•Affects multiple organs

•Inhibits eukaryotic protein translation

•Causes DNA strand breaks

•Mostly found in tropical

Saxitoxins •A group of ~20

structurally relatedalkaloids

•Bind to voltage gatedNa+ channels

•Paralysis and death •LD50 10μg kg-1 (i.p.

mouse)

Anatoxin-a •Small molecular

weight alkaloid thatmimics acetylcholine

•7 structural variantsknown to exist

•Structural analogue ofcocaine

•Death by paralysisand asphyxiation

LPS endotoxinsCharacteristic of Gram negative bacteria (including cyanobacteria)Found in the outer layer of the cell wallThe lipid A component responsible for human health effectsFever, vomiting, diarrhoea and inflammation

BMAA- a newcyanobacterial toxin?

•Non-protein amino acid •Binds to glutamic acid

receptors •Acutely neurotoxic to

primates in high doses •Associated with an

incidence of Motor NeuronDisease

cyanobacteria and the toxins they produceGenus Toxins producedAnabaena Anatoxins, Microcystins, SaxitoxinsAnabaenopsis MicrocystinsAphanizomenon Saxitoxins, CylindrospermopsinsCylindrospermopsis Cylindrospermopsins, SaxitoxinsHapalosiphon MicrocystinsLyngbya Aplysiatoxins, Lyngbyatoxin aMicrocystis MicrocystinsNodularia NodularinNostoc MicrocystinsPhormidium (Oscillatoria) Anatoxin

Planktothrix (Oscillatoria)Anatoxins, Aplysiatoxins, Microcystins, Saxitoxins

Schizothrix AplysiatoxinsTrichodesmium yet to be identifiedUmezakia Cylindrospermopsin

* Not all species within a genus produce the same toxins. In addition to these toxins, many other bioactive compounds have been isolated from cyanobacteria. Some have been determined to be toxic to specific organisms and are potentially toxic to humans.

Impacts on Human Health

•Gastrointestinal upsets(USA, Zimbabwe, UK, Australia,

Sweden) •Contact dermatitis, mucosal

irritation(Pacific Islands,UK, USA, Norway,

Australia) •Liver damage (Brazil, Australia)

•Kidney damage (Australia) •Neurological damage (Brazil)

•Pulmonary consolidation (atypical pneumonia, UK)

Potential Long-Term Health Effects

•Microcystins –Tumour promotion

•Nodularin –Tumour promotion and possible

carcinogenicity •Cylindrospermopsin

–Carcinogenicity through effects on DNA

•BMAA –Possible association with human

neurodegeneration

Exposure routes

•Drinking water •Diet

•Dermal •Pulmonary

•Haemodialysis

Human health incidents •Itaparica Dam

–Gastrointestinal upset (2000 cases)

–88 deaths over a 42 day period –Microcystis and Anabaena

present in water –Cyanotoxins thought to be the

cause •Primary liver cancer in China“ –Hot spots” related to drinking

water supply –Surface vs. well water

CLIMATE CHANGEinternationally agreed that

cyanobacterialBlooms will increase in geographical spread, population density and seasonal duration

Examination of the evolutionary history of cyanobacteria, studies of theirecophysiology, and recent investigations of phytoplankton dynamics andcommunity structure in response to global climate change all suggest thatcyanobacteria will probably thrive under environmental conditions associatedwith global warming.

Any Question ??

The Team

Thank You for Your Attention