Manganese-oxidizing bacteria isolated from natural and technical systems remove cylindrospermopsin

The cyanotoxin cylindrospermopsin was discovered during a drinking water-related outbreak of human poisoning in 1979. Knowledge about the degradation of cylindrospermopsin in waterbodies is limited. So far, only few cylindrospermopsin-removing bacteria have been described. Manganese-oxidizing bacteria remove a variety of organic compounds. However, this has not been assessed for cyanotoxins yet. We investigated cylindrospermopsin removal by manganese-oxidizing bacteria, isolated from natural and technical systems. Cylindrospermopsin removal was evaluated under different conditions. We analysed the correlation between the amount of oxidized manganese and the cylindrospermopsin removal, as well as the removal of cylindrospermopsin by sterile biogenic oxides. Removal rates in the range of 0.4-37.0 μg L^-1 day^-1 were observed. When MnCO₃ was in the media Pseudomonas sp. OF001 removed ∼100% of cylindrospermopsin in 3 days, Comamonadaceae bacterium A210 removed ∼100% within 14 days, and Ideonella sp. A288 and A226 removed 65% and 80% within 28 days, respectively. In the absence of Mn²⁺, strain A288 did not remove cylindrospermopsin, while the other strains removed 5-16%. The amount of manganese oxidized by the strains during the experiment did not correlate with the amount of cylindrospermopsin removed. However, the mere oxidation of Mn²⁺ was indispensable for cylindrospermopsin removal. Cylindrospermopsin removal ranging from 0 to 24% by sterile biogenic oxides was observed. Considering the efficient removal of cylindrospermopsin by the tested strains, manganese-oxidizing bacteria might play an important role in cylindrospermopsin removal in the environment. Besides, manganese-oxidizing bacteria could be promising candidates for biotechnological applications for cylindrospermopsin removal in water treatment plants.