Growth responses of achlorophyllous Euglena gracilis to selected concentrations of cadmium and pentachlorophenol.

The growth response of a wild achlorophyllous Euglena gracilis mutant was studied during exposure to cadmium and pentachlorophenol (PCP). Cadmium gradually reduced the growth rate and terminal cell density; PCP only lengthened the initial lag phase relative to control cultures. Flow cytometry showed that cadmium altered the cell cycle by delaying late S and G2/M phases; PCP did not disturb the cell cycle, but markedly affected DNA staining: the intercalating dyes ethidium bromide and propidium iodide showed little staining compared to controls. However, replication and transcription processes were not altered by PCP, as cell division occurred normally. Cells surviving after PCP treatment apparently developed an adaptative response during the lag phase.