Toxicity of polychlorinated biphenyls (PCBs) to Euglena gracilis: cell population growth, carbon fixation, chlorophyll level, oxygen consumption, and protein and nucleic acid synthesis.

Populations of Euglena gracilis in exponential growth under light were exposed to 2.5, 5.0, 7.5, and 10 ppm of Aroclor 1221. The ID50/48 of Aroclor 1221 was estimated to be 4.4 ppm, while Aroclor 1232 tested at 20, 35, 50, and 100 ppm resulted in an id50/48 of 55 ppm. With Aroclor 1242, no inhibition of growth was observed with up to 100 ppm exposure. Cell cultures exposed to 4.4 ppm of Aroclor 1221 for 48 hrs had a significantly reduced rate of carbon fixation and reduced levels of chlorophyll after correction for cell density. Oxygen consumption was not affected at the ID50 level of the Aroclor. Uptake of [3H]-leucine in treated cultures was twice that of controls, and [3H]-uridine uptake was significantly lower. Uptake of [3H]-thymidine, and incorporation of [3H]-leucine, [3H]-thymidine, and [3H]-uridine were not significantly different in treated and control cultures. Thes results suggest that at the ID50 level, polychlorinated biphenyls (PCBs) reduce cell population growth in Euglena gracilis by inhibition of photosynthesis and/or chlorophyll production.