Molecular Basis for Detection and Cytotoxicity Caused by
Cyanobacterial Producing Microcystin in Harmful Algal Blooms
Steve Mauro, Ph.D.
Gannon University
mauro003@gannon.edu
Cyanobacteria are common in freshwater environments
- These are bacteria capable of
undergoing photosynthesis
- They produce approximately 25%
of the worlds oxygen
Bacteroidetes
Proteobacteria
Cyanobacteria
- In Presque Isle beach water, cyanobacteria
compromise approximately 27% of bacterial
content
Certain cyanobacterial strains can produce toxins
- These cyanobacterial types become
more prevalent as the summer
progresses
- Many aggregate together in a bloom
- Temperature, nutrient content, and
buoyancy are some factors involved
in propagating harmful algal blooms
INSERT PICTURE OF BLOOM HERE!!!
Toxin producing cyanobacterial genera include:
- Microcystis
- Plankothrix
- Anabaena
- Nodularia
Toxin expression
The toxin is produced due to the expression from a mcy gene cluster
There are many variants of this toxin that alter specific toxic impact
Gene regulatory mechanisms are not clear but expression appears to be constitutively
active in environmental samples
Toxin Etiology
The microcystin toxin is transported into cells and acts by hyperphosphorylating proteins
-
Can lead to:
Nausea/vomiting
Intrahepatic bleeding
Cancer
Skin irritation
Acute respiratory pneumonia
Gastroenteritis
WHO guidelines for concentration of microcystin exposure
Water type
Risk level
Microcystin
concentration
Cyanobacteria
concentration
Drinking water
High
1 ppb
Not detected
Recreational
water
Low
1-4 ppb
< 5,000 cells/mL
Recreational
water
Moderate
4-20 ppb
5,000-20,000
cells/mL
Recreational
water
High
>20 ppb
100,000
cells/mL
Concentrations found thus far in Presque Isle water samples using ELISA assay
Avg. concentration microcystin (ppb)
7
6
5
4
3
2
1
0
Beach samples-no bloom Bay samples- no bloom
Bay samples- bloom
Conclusions/future perspectives
Cyanobacteria is a common component of the Presque Isle ecosystem
Microcystin is consistently present in Presque Isle bathing waters in the absence of
a bloom at what would be considered acceptable levels of exposure
Blooms have been detected in the Bay at levels that pose slight to moderate risk to humans
Ongoing research and monitoring efforts are needed to better understand the spatial and
temporal factors that drive mcy gene expression and harmful algal bloom formation
Funding Sources
Regional Science Consortium