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The killer cyanobacteria: a molecular biology approach
to a global environmental problem Cyanobacteria are a heterogeneous group of oxygenic phototrophic bacteria with a long evolutionary history. They can live almost everywhere on earth and show a great diversity of cell morphology. They express diverse physiological properties such as: photosynthesis, nitrogen fixation, cell differentiation, and -economically most important- toxin formation. Mass occurrence of cyanobacteria (cyanobacterial blooms) are common in fresh, brackish and marine waters all over the world. The blooms affect not only water taste, odor and appearance but also they are often toxic to wild life, domestic animals and humans. Anthropogenic activities such as increased nutrient loading in freshwater and coastal areas have lead to the increase of cyanobacterial blooms worldwide. Report s of poisoning of humans and cattle range from the first report of toxic cyanobacterial bloom in a lake in Australia in 1878, to high incidence of liver cancer in China due to the presence of cyanotoxins in drinking-water in 1989 and 1996, to the tragic death of 60 dialysis patients in Brazil in 1996 due to the presence of cyanotoxins in the water supply used in haemodialysis unit. Yet, cyanobacteria play global important roles, they are major contributors to the global carbon and nitrogen cycles and their activities are vital for maintaining healthy ecosystems. For example about 50% of the total annual nitrogen fixed per year in tropical oceans is due to the nitrogen fixation activity of one bloom- forming cyanobacterium! The fixed N produced represents a source of extremely valuable "new" nitrogen in this ecosystem (limited in reduced form of N), which is vital for the growth of other organisms, ranging from microbes to plants, algae and fish. Without a deep understanding of the biology of the cyanobacterial species that form the toxic blooms there can be no effective control of toxic blooms and no effective management of water bodies. Cyanotoxins are cyclic peptides, alkaloids and lipopolysaccharides. In this project we focus on a cyclic peptide called nodularin that is produced by the cyanobacterium Nodularia spumigena. N. spumigena often form toxic blooms during the summer in the Baltic Sea. Using up-to-date molecular biology techniques such as proteomics, real time PCR and microarrays, we are investigating the biology of N. spumigena during nitrogen fixation and nodularin production. The results of this study will refine our knowledge of the killer cyanobacteria and will significantly contribute to the efforts exerted world wide to manage cyanobacterial blooms in a sustainable way. For this project, we are looking for a highly motivated student with a good background in biology. Supervisor: Rehab El-Shehawy, Assistant Prof. Dept. of Botany, Stockholm University. Co-supervisor: Birgitta Bergman, Professor. Dept.of Botany, Stockholm University. |
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