Elevated microcystin and nodularin levels in cyanobacteria growing in spent medium of Planktothrix agardhii

Some cyanobacteria (blue-green algae) are able to produce potent toxins, of which one group are the hepatotoxic peptides, the microcystins and the nodularins. In this study, we report the effect of the non-toxic cyanobacterium Planktothrix agardhii CYA29 and its spent medium on the toxin levels of Microcystis aeruginosa PCC7820 and Nodularia sp. PCC7804. Microcystin levels were elevated when P. agardhii or spent medium were added to cultures of M. aeruginosa PCC7820. This effect was also observed for two nodularin variants in Nodularia PCC7804. However, growth of M. aeruginosa in its own spent medium did not lead to elevated microcystin levels.