Alterations in the structure of phycobilisomes of the cyanobacterium, Spirulina platensis in response to enhanced Na+ level

Incubation of Spirulina platensis at enhanced Na+ concentrations resulted i n 30% increased intracellular accumulation of Na+ ions. This accumulation o f Na+ ions intracellularly altered the phycobilisome organization as reveal ed by transmission electron microscopic data and changes in the absorption spectrum. The room temperature emission peak at 638 nm in the control sampl e was blue-shifted by 7 nm in the treated samples suggesting phycobilisome disorganization. SDS-PAGE of phycobilisome polypeptides showed a significan t increase in a 66.2 kDa polypeptide. This is the first report that the enh anced concentration of intracellular Na+ ion alters the structure of the ph ycobilisome in S. platensis.