Microevolution of toxin synthesis in cyanobacteria

Cyanobacteria (blue green algae) do occur frequently in surface water and contain an enormous high diversity of bioactive compounds. Typically isolates of the same species differ in composition of small bioactive peptides but cannot be discriminated in the microscope. Nothing is known about the mechanisms and recombination processes affecting existing pathways of secondary metabolite synthesis. In a previous project P15709 we have identified a number of DNA rearrangements and mutations within gene regions (mcy) involved in the synthesis of the toxic peptide microcystin (MC) which are either linked to specific structural variants differing in bioactivity or complete inactivation of the total mcy gene cluster (55 000 base pairs in length). Structural variants specific to populations found in a specific lake have been found. It is the aim of the study (i) to find out whether genetic divergence in microcystin synthesis is possible in spatially separated populations although the theoretical unlimited dispersal capability of microorganisms; (ii) to test the hypothesis that the abundance of mutations and rearrangements might be explained by transposable elements; (iii) to differentiate between mutations of genes caused by transposable elements and caused by the degradation of genes; (iv) to find out the variation in abundance of specific mutations and unspecific mcy inactivation in nature; (v) to understand the physiological consequences of DNA rearrangements and mutations via the detection of the MC synthetase. For this purpose nine mcy genotypes containing either specific mutations or functional rearrangements of the mcy gene cluster will be quantified in populations of the cyanobacterium Planktothrix in ten lakes and four lake inflows by modern quantitative real-time PCR technique (the Taq nuclease assay) and the data evaluated using multivariate statistics. In addition flanking regions of DNA rearrangements and mutations detected in field samples and in isolates will be genetically analysed for monophyly vs. polyphyly and signs of degradation of the mcy genes. The expression of the MC synthetase in isolates will be monitored via immunodetection techniques. This two year project will be among the first within the discipline of aquatic ecology that will be able to link molecular insights with ecological research and deliver information on the mechanisms favouring the impressive diversity in synthesis of secondary metabolites.

Cyanobacteria (blue green algae) do occur frequently in surface water and contain an enormous high diversity of bioactive compounds. Typically isolates of the same species differ in composition of small bioactive peptides but cannot be discriminated in the microscope. Nothing is known about the mechanisms and recombination processes affecting existing pathways of secondary metabolite synthesis. In a previous project P15709 we have identified a number of DNA rearrangements and mutations within gene regions (mcy) involved in the synthesis of the toxic peptide microcystin (MC) which are either linked to specific structural variants differing in bioactivity or complete inactivation of the total mcy gene cluster (55 000 base pairs in length). Structural variants specific to populations found in a specific lake have been found. It is the aim of the study 1. to find out whether genetic divergence in microcystin synthesis is possible in spatially separated populations although the theoretical unlimited dispersal capability of microorganisms; 2. to test the hypothesis that the abundance of mutations and rearrangements might be explained by transposable elements; 3. to differentiate between mutations of genes caused by transposable elements and caused by the degradation of genes; 4. to find out the variation in abundance of specific mutations and unspecific mcy inactivation in nature; 5. to understand the physiological consequences of DNA rearrangements and mutations via the detection of the MC synthetase. For this purpose nine mcy genotypes containing either specific mutations or functional rearrangements of the mcy gene cluster will be quantified in populations of the cyanobacterium Planktothrix in ten lakes and four lake inflows by modern quantitative real-time PCR technique (the Taq nuclease assay) and the data evaluated using multivariate statistics. In addition flanking regions of DNA rearrangements and mutations detected in field samples and in isolates will be genetically analysed for monophyly vs. polyphyly and signs of degradation of the mcy genes. The expression of the MC synthetase in isolates will be monitored via immunodetection techniques. This two year project will be among the first within the discipline of aquatic ecology that will be able to link molecular insights with ecological research and deliver information on the mechanisms favouring the impressive diversity in synthesis of secondary metabolites.