title: Casting a net: fibres produced by Microcystis sp. in field and laboratory populations.
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.
authors.affiliation: The Alexander Silberman Institute of Life Sciences, Edmond J. Safra Campus, Givat Ram, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel The Yigal Allon Kinneret Limnological Laboratory, Israel Oceanographic and Limnological Research, PO Box 447, Migdal 14950, Israel Department of Genetic Toxicology and Cancer Biology, National Institute of Biology, Ljubljana, Slovenia Institute of Biochemistry and Biology, University of Potsdam, 14476 Golm, Germany.
authors.forename: Moshe
authors.initials: M
authors.lastname: Harel
authors.forename: Gad
authors.initials: G
authors.lastname: Weiss
authors.forename: Einat
authors.initials: E
authors.lastname: Daniel
authors.forename: Avraham
authors.initials: A
authors.lastname: Wilenz
authors.forename: Ora
authors.initials: O
authors.lastname: Hadas
authors.forename: Assaf
authors.initials: A
authors.lastname: Sukenik
authors.forename: Bojan
authors.initials: B
authors.lastname: Sedmak
authors.forename: Elke
authors.initials: E
authors.lastname: Dittmann
authors.forename: Sergei
authors.initials: S
authors.lastname: Braun
authors.forename: Aaron
authors.initials: A
authors.lastname: Kaplan