Distribution and abundance of nontoxic mutants of cyanobacteria in lakes of the Alps.

摘要: The filamentous cyanobacterium Planktothrix rubescens frequently occurs in deep and stratified lakes the temperate region of northern hemisphere is a known producer hepatotoxic secondary metabolite microcystin. These cyclic heptapeptides are synthesized nonribosomally via large enzyme complexes encoded by microcystin (mcy) synthetase gene cluster. occurrence cyanobacterial strains lacking microcystin, but containing mcy cluster has been reported repeatedly; it was shown that this inactivation due to mutations such as deletion events insertion transposable elements. In present study, 12 Austria, Germany, Switzerland were sampled from July 2005 October 2007, proportion inactive genotypes quantified relation total population red-pigmented means quantitative polymerase chain reaction. total, four different quantified, namely two insertions affecting mcyD, one mcyA, within mcyH mcyA. occurred over wide range densities (40-570,000 filaments L(-1)), their abundance found be positively correlated with density. However, on average, all nontoxic mutants low only (min 0%, mean 6.5% +/- 1.1 (SE), max 52% population). genotype mcyHA had significantly higher 3.7% 1, 52%) when compared 2.8% 0.7, 24%). results demonstrate linearly related density, selective sweeps did not occur during transition prebloom bloom conditions.