Role of microcystin in oxidative stress acclimation in the cyanobacterium Microcystis aeruginosa

• Applicant: Professorin Dr. Elke Dittmann-Thünemann
• Subject Area: Microbial Ecology and Applied Microbiology ; Plant Physiology
• Term: from 2010 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 177188285

Microcystin is a peptide toxin that is produced by various genera of bloom-forming freshwater cyanobacteria. The biosynthesis of the cyclic heptapeptide is achieved on a complex of non-ribosomal peptide synthetases (NRPS) and polyketide synthases (PKS). The toxins are capable of forming a covalent bond to eukaryotic protein phosphatases. We could show that microcystin binds to cysteines of a set of proteins in the producing cyanobacterium Microcystis. Interestingly, the binding partners include the key enzyme of the Calvin cycle, Rubisco. Binding of microcystin is strongly enhanced under conditions triggering oxidative stress. Moreover, the lack of microcystin in the mutant leads to a clear increase in the sensitivity against oxidative stress. Together, these data support a physiological function of microcystin in the natural producer. We suggest a redox-dependent protein-modulating role for microcystin. This would be an entirely new function for a complex secondary metabolite that could provide hints on the functionality of other secondary metabolites. Moreover, the proposed role of microcystin may reflect the ecological diversity of oxidative stress acclimation mechanisms in cyanobacteria. Understanding the role of microcystin can assist in the development of new management strategies of toxic cyanobacteria.

• DFG Programme: Research Grants