TY  - JOUR
A1  - Harel, Moshe
A1  - Weiss, Gad
A1  - Daniel, Einat
A1  - Wilenz, Avraham
A1  - Hadas, Ora
A1  - Sukenik, Assaf
A1  - Sedmak, Bojan
A1  - Dittmann-Thünemann, Elke
A1  - Braun, Sergei
A1  - Kaplan, Aaron
T1  - Casting a net fibres produced by Microcystis sp in field and laboratory populations
JF  - Environmental microbiology reports
N2  - 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.
Y1  - 2012
U6  - https://doi.org/10.1111/j.1758-2229.2012.00339.x
SN  - 1758-2229
VL  - 4
IS  - 3
SP  - 342
EP  - 349
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Kaplan, Aaron
A1  - Harel, Moshe
A1  - Kaplan-Levy, Ruth N.
A1  - Hadas, Ora
A1  - Sukenik, Assaf
A1  - Dittmann-Thünemann, Elke
T1  - The languages spoken in the water body (or the biological role of cyanobacterial toxins)
JF  - Frontiers in microbiology
N2  - Although intensification of toxic cyanobacterial blooms over the last decade is a matter of growing concern due to bloom impact on water quality, the biological role of most of the toxins produced is not known. In this critical review we focus primarily on the biological role of two toxins, microcystins and cylindrospermopsin, in inter- and intra-species communication and in nutrient acquisition. We examine the experimental evidence supporting some of the dogmas in the field and raise several open questions to be dealt with in future research. We do not discuss the health and environmental implications of toxin presence in the water body.
KW  - aoa
KW  - cylindrospermopsin
KW  - microcystin
KW  - cyr
KW  - mcy
Y1  - 2012
U6  - https://doi.org/10.3389/fmicb.2012.00138
SN  - 1664-302X
VL  - 3
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Zilliges, Yvonne
A1  - Kehr, Jan-Christoph
A1  - Meissner, Sven
A1  - Ishida, Keishi
A1  - Mikkat, Stefan
A1  - Hagemann, Martin
A1  - Kaplan, Aaron
A1  - Börner, Thomas
A1  - Dittmann-Thünemann, Elke
T1  - The cyanobacterial hepatotoxin microcystin binds to proteins and increases the fitness of microcystis under oxidative stress conditions
JF  - PLoS one
N2  - 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.
Y1  - 2011
U6  - https://doi.org/10.1371/journal.pone.0017615
SN  - 1932-6203
VL  - 6
IS  - 3
PB  - PLoS
CY  - San Fransisco
ER  -