King Saud University College of Science
Microbiology Department
By: Abdelrahman A. Dawoud Yasser Al HajajFaisal l Mutairy
Mohammed Ansari
Prof. Ibraheem IBM
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
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
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.