Control by Iron of Chlorophyll Formation and Growth in Euglena gracilis

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Abstract
When E. gracilis were grown first under low light intensity and then shaken under high light intensity in a non-nutrient buffer, chlorophyll was synthesized rapidly with high repeatability, and in absolute dependence on the Fe content of the cells. Chlorophyll formation in Fe-deficient cells was promoted by Fe but not by other components of the growth medium. The Fe deficiency "lesion" was partially and specifically reversible. A graph of chlorophyll synthesis as a function of the Fe content of the cells shows the rate of chlorophyll synthesis rising linearly from zero to a saturating value of Fe, behind which the rate remains constant over a 20-fold range of Fe contents. Chlorophyll synthesis was as little as 1/3 of control rates at Fe contents where growth remained normal. Chlorophyll synthesis occurred without net synthesis of protein and was not inhibited by 2,4-dinitrophenol. The form of the newly found chlorophyll appears to be principally chlorophyllide a.