Spatial divergence in the proportions of genes encoding toxic peptide synthesis among populations of the cyanobacterium Planktothrix in European lakes

It has been frequently reported that seasonal changes in toxin production by cyanobacteria are due to changes in the proportion of toxic/nontoxic genotypes in parallel to increases or decreases in population density during the seasonal cycle of bloom formation. In order to find out whether there is a relationship between the proportion of genes encoding toxic peptide synthesis and population density of Planktothrix spp. we compared the proportion of three gene regions that are indicative of the synthesis of the toxic heptapeptide microcystin ( mcy B), and the bioactive peptides aeruginoside ( aer B) and anabaenopeptin ( apn C) in samples from 23 lakes of five European countries ( n =153). The mcy B, aer B, and apn C genes occurred in 99%, 99%, and 97% of the samples, respectively, and on average comprised 60 ± 3%, 22 ± 2%, and 54 ± 4% of the total population, respectively. Although the populations differed widely in abundance (10 −3 –10 3  mm 3  L −1 ) no dependence of the proportion of the mcy B, aer B, and apn C genes on the density of the total population was found. In contrast populations differed significantly in their average mcy B, aer B, and apn C gene proportions, with no change between prebloom and bloom conditions. These results emphasize stable population‐specific differences in mcy B, aer B, and apn C proportions that are independent from seasonal influences.