Microcystin production revisited: conjugate formation makes a major contribution.
The impact of environmental stimuli on the production of the widespread cyanobacterial hepatotoxin microcystin (MC) is under debate. Whereas transcriptional studies of the biosynthetic genes suggest a clear influence of light conditions on toxin production the data for the metabolite itself are inconsistent and highly strain-specific. Here, we have reassessed the MC content by using two immunological detection techniques that allow a parallel quantification of MC in the methanolic extracts and the residual pellet fraction that contains high molecular weight proteins. Our results show a significant proportion of MC in the protein bound fraction in strains of Microcystis and Planktothrix and of the related toxin nodularin (NOD) in Nodularia. Moreover, we could show a very strong increase of MC after high light illumination in the protein fraction contributing to a significant overall increase in MC production under these conditions that is not seen in extracts analysed by LC-MS and ELISA. The fact that a considerable portion of MC is neglected with current analysis techniques was also confirmed for selected field samples. Immunofluorescence studies suggest strain-specific differences in the amount of MC conjugate formation.
Department of Microbiology, Institute of Biochemistry and Biology, University of Potsdam, Golm, Germany.
Sven
S
Meissner
Jutta
J
Fastner
Elke
E
Dittmann
D002853:Chromatography, Liquid; D000458:Cyanobacteria / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects; D004797:Enzyme-Linked Immunosorbent Assay; D008027:Light; D013058:Mass Spectrometry; D000432:Methanol / Q000737:chemistry; D052998:Microcystins / Q000032:analysis / Q000378:metabolism*; D011485:Protein Binding
D052998:Microcystins; C078588:microcystin; D000432:Methanol