PARENT SESSION
Posters P4C Controling CO₂: Stomates and carbon concentrating mechanisms. Abstracts (631-642)

Investigation of carbon and light on cyanobacterial toxin production. Douglas Graham^*,1, Linda Lawton¹, ¹ School of Life Sciences, Aberdeen, Scotland UK

ABSTRACT- Cyanobacteria (blue green algae) are a widely distributed and diverse group of unicellular and multicellular photosynthetic prokaryotes. They are known to produce toxic secondary metabolites that fall into two main classes, hepatotoxins and neurotoxins the function of which is still unclear. Globally the most commonly occurring toxins are hepatotoxins, microcystin and nodularin often found in the bloom forming genera Microcystis, Anabaena, Nostoc and Oscillatoria. Typically found in eutrophic water bodies and slow moving rivers, they pose a significant hazard to both human and animal health following ingestion of contaminated water. The implication of toxic bloom formation is a major concern for water management; therefore understanding the natural function of these secondary metabolites may help in treatment. Research has primarily focused on the effect of environmental factors like light, temperature, pH, limited nutrients and micronutrients, but all the findings have produced no clear indication of these factors being responsible for the regulation of toxin production. Our research into the effects of increasing inorganic carbon and light intensity on hepatotoxin production in Microcystis aeruginosa, Microcystis sp. and Nodularia spumigenia, found significant changes in the levels of toxin produced. Increasing inorganic carbon reduced levels of biomass and cause significant reductions in the level of intracellular microcystin and nodularin. In the most profound case an 80%reduction in the intracellular level of microcystin was observed when grown in the presence of 40mM sodium bicarbonate. Also previous studies have suggested that toxins are only released after cell lysis, but in the presence of increased inorganic carbon and light the extracellular toxin level exceeded the intracellular levels in cultures of N. spumigenia.

KEY WORDS: Microcystis aeruginosa , inorganic carbon, light, hepatotoxins, microcystin