Abstract
Phosphate-starved Chlorella pyrenoidosa cells formed polyphosphate bodies (PB) upon transfer into nutrient solutions containing phosphate and potassium, or another monovalent cation, such as Na(+), NH(4) (+), Li(+), or Rb(+). The phenomenon was studied by chemical analyses, light microscopy, and electron microscopy.When the P-starved cells were transferred into a complete nutrient solution containing 100 micromolar P, they accumulated large quantities of P and K within several hours. 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 micromolar H(3)PO(4) and 100 micromolar KHCO(3) responded in a similar manner as the cells exposed to the complete nutrient solution. However, the PB appeared structurally different.It is proposed that 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.