We have investigated the physiological response of marine planktonic cyanobacteria to UV-A (320-390 nm) irradiation. Here, we report the isolation of a UV-A absorbing pigment from a UV-A resistant strain of Oscillatoria. This pigment has been purified, and its structure determined to be biopterin glucoside (BG), a compound chemically related to the pteridine pigments found in butterfly wings. A UV-A sensitive isolate did not produce significant levels of this chromophore. UV-A radiation was very effective in eliciting synthesis of BG. In addition, increased UV-A radiation, increased intracellular levels of BG. These data suggest that BG may protect the cyanobacterium from adverse effects of UV-A radiation.
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