Determination of oligopeptide diversity within a natural population of Microcystis spp. (Cyanobacteria) by typing single colonies by matrix-assisted laser desorption ionization-time of flight mass spectrometry

Besides the most prominent peptide toxin, microcystin, the cyanobacteria Mi crocystis spp. have been shown to produce a large variety of other bioactiv e oligopeptides. We investigated for the first time the oligopeptide divers ity within a natural Microcystis population by analyzing single colonies di rectly vith matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The results demonstrate a high diversity of k nown cyanobacterial peptides such as microcystins, anabaenopeptins, microgi nins, aeruginosins, and cyanopeptolins,, but also many unknown substances i n the Microcystis colonies. Oligopeptide patterns were mostly related to sp ecific Microcystis taxa. Microcystis aeruginosa (Kutz.) Kutz. colonies cont ained mainly microcystins, occasionally accompanied by aeruginosins. In con trast, microcystins were not detected in Microcystis ichthyoblabe Kutz.; in stead, colonies of this species contained anabaenopeptins and/or microginin s 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 chemota xonomic tool within the genus Microcystis is discussed. It could be demonst rated that the typing of single colonies by MALDI-TOF MS may be a valuable tool for ecological studies of the genus Microcystis as well as in early wa rning of toxic cyanobacterial blooms.