Association of Potassium and Some Other Monovalent Cations with Occurrence of Polyphosphate Bodies in Chlorella pyrenoidosa

Abstract

Phosphate-starved C. pyrenoidosa cells formed polyphosphate bodies (PB) upon transfer into nutrient solutions containing phosphate and K, or another monovalent cation, such as Na+, NH4+, Li+, or Rb+. The phenomenon was studied by chemical analyses, light microscopy and EM. When the P-starved cells were transferred into a complete nutrient solution containing 100 .mu.molar P, they accumulated large quantities of P and K within several h. The accumulation was accompanied by a corresponding appearance of PB in the cells. The absence of K from the medium prevented appreciable P accumulation and PB formation, but omitting Ca or Mg did not. The P-starved cells exposed to a simple solution of at least 20 .mu.molar H3PO4 and 100 .mu.molar KHCO3 responded in a similar manner as the cells exposed to the complete nutrient solution. However, the PB appeared structurally different. Apparently monovalent cations are essential for PB formation in C. pyrenoidosa. K is suggested to be a major component of PB formed in K-sufficient media.