Time-dependent alterations in the antenna pigment-protein complex by mercury ions in the cyanobacterium Spirulina platensis

We have shown that mercury affects energy transfer in Spirulina platensis. It inhibits energy transfer from phycocyanin to chlorophyll a by specifically bleaching the -84 chromophore of the chromo protein, phycocyanin (PC), in the cyanobacterium. This effect is observed during short-term exposure of cells to Hg²⁺ ions. Upon long-term (12 h) exposure, mercury at low concentrations (1–2.5 m) causes the gradual degradation of the polypeptide (22 kDa) of the PC of phycobilisomes in this cyanobacterium. The effect of mercury on this polypeptide is significant compared with the other phycobiliproteins.