PROTOANEMONIN-INDUCED CYTOTOXIC EFFECTS IN EUGLENA-GRACILIS

The changes that protoanemonin, an antimicrobial agent of natural orig in, brought about in the alga Euglena gracilis were studied with light and electron microscopy and with flow cytometry. The compound proved lethal for the alga at a dose of 5 x 10(-5) M. At the sublethal dose o f 3.5 x 10(-5) M it caused: marked inhibition of growth; increase in t he average cell volume; inhibition of cytokinesis and induction of coe nocytic organisms; loss of the flagellum and stigma. Most nuclei were arrested in the G2/M phase of the cellular cycle. The chloroplasts wer e still well organized, but there was a conspicuous decrease in carote noids and chlorophylls a and b, with a corresponding increase in pheop hytins. The multifarious alterations seen in Euglena are discussed on the basis of a possible interaction between this lactone and several e nzymatic systems. (C) 1997 Academic Press Limited.