@article{HarelWeissDanieletal.2012,
  author    = {Harel, Moshe and Weiss, Gad and Daniel, Einat and Wilenz, Avraham and Hadas, Ora and Sukenik, Assaf and Sedmak, Bojan and Dittmann-Th{\"u}nemann, Elke and Braun, Sergei and Kaplan, Aaron},
  title     = {Casting a net fibres produced by Microcystis sp in field and laboratory populations},
  series = {Environmental microbiology reports},
  volume    = {4},
  journal   = {Environmental microbiology reports},
  number    = {3},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  issn      = {1758-2229},
  doi       = {10.1111/j.1758-2229.2012.00339.x},
  pages     = {342 -- 349},
  year      = {2012},
  abstract  = {The reasons for the apparent dominance of the toxic cyanobacterium Microcystis sp., reflected by its massive blooms in many fresh water bodies, are poorly understood. We show that in addition to a large array of secondary metabolites, some of which are toxic to eukaryotes, Microcystis sp. secretes large amounts of fibrous exopolysaccharides that form extremely long fibres several millimetres in length. This phenomenon was detected in field and laboratory cultures of various Microcystis strains. In addition, we have identified and characterized three of the proteins associated with the fibres and the genes encoding them in Microcystis sp. PCC 7806 but were unable to completely delete them from its genome. Phylogenetic analysis of the most abundant one, designated IPF-469, showed its presence only in cyanobacteria. Its closest relatives were detected in Synechocystis sp. PCC 6803 and in Cyanothece sp. strains; in the latter the genomic organization of the IPF-469 was highly conserved. IPF-469 and the other two proteins identified here, a haloperoxidase and a haemolysin-type calcium-binding protein, may be part of the fibres secretion pathway. The biological role of the fibres in Microcystis sp. is discussed.},
  language  = {en}
}
@article{ZilligesKehrMeissneretal.2011,
  author    = {Zilliges, Yvonne and Kehr, Jan-Christoph and Meissner, Sven and Ishida, Keishi and Mikkat, Stefan and Hagemann, Martin and Kaplan, Aaron and B{\"o}rner, Thomas and Dittmann-Th{\"u}nemann, Elke},
  title     = {The cyanobacterial hepatotoxin microcystin binds to proteins and increases the fitness of microcystis under oxidative stress conditions},
  series = {PLoS one},
  volume    = {6},
  journal   = {PLoS one},
  number    = {3},
  publisher = {PLoS},
  address   = {San Fransisco},
  issn      = {1932-6203},
  doi       = {10.1371/journal.pone.0017615},
  pages     = {11},
  year      = {2011},
  abstract  = {Microcystins are cyanobacterial toxins that represent a serious threat to drinking water and recreational lakes worldwide. Here, we show that microcystin fulfils an important function within cells of its natural producer Microcystis. The microcystin deficient mutant Delta mcyB showed significant changes in the accumulation of proteins, including several enzymes of the Calvin cycle, phycobiliproteins and two NADPH-dependent reductases. We have discovered that microcystin binds to a number of these proteins in vivo and that the binding is strongly enhanced under high light and oxidative stress conditions. The nature of this binding was studied using extracts of a microcystin-deficient mutant in vitro. The data obtained provided clear evidence for a covalent interaction of the toxin with cysteine residues of proteins. A detailed investigation of one of the binding partners, the large subunit of RubisCO showed a lower susceptibility to proteases in the presence of microcystin in the wild type. Finally, the mutant defective in microcystin production exhibited a clearly increased sensitivity under high light conditions and after hydrogen peroxide treatment. Taken together, our data suggest a protein-modulating role for microcystin within the producing cell, which represents a new addition to the catalogue of functions that have been discussed for microbial secondary metabolites.},
  language  = {en}
}