Determination of Oligopeptide Diversity within a Natural Population ofMicrocystisspp. (Cyanobacteria) by Typing Single Colonies by Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

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Abstract
Besides the most prominent peptide toxin, microcystin, the cyanobacteriaMicrocystisspp. have been shown to produce a large variety of other bioactive oligopeptides. We investigated for the first time the oligopeptide diversity within a naturalMicrocystispopulation by analyzing single colonies directly with matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS). The results demonstrate a high diversity of known cyanobacterial peptides such as microcystins, anabaenopeptins, microginins, aeruginosins, and cyanopeptolins, but also many unknown substances in theMicrocystiscolonies. Oligopeptide patterns were mostly related to specificMicrocystistaxa.Microcystis aeruginosa(Kütz.) Kütz. colonies contained mainly microcystins, occasionally accompanied by aeruginosins. In contrast, microcystins were not detected inMicrocystis ichthyoblabeKütz.; instead, colonies of this species contained anabaenopeptins and/or microginins or unknown peptides. Within a third group,Microcystis wesenbergii(Kom.) Kom. in Kondr., chiefly a cyanopeptolin and an unknown peptide were found. Similar patterns, however, were also found in colonies which could not be identified to species level. The significance of oligopeptides as a chemotaxonomic tool within the genusMicrocystisis discussed. It could be demonstrated that the typing of single colonies by MALDI-TOF MS may be a valuable tool for ecological studies of the genusMicrocystisas well as in early warning of toxic cyanobacterial blooms.

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