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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 1268

Robert W. Sanders and Cynthia C. Gilmour; Accumulation of selenium in a model freshwater microbial food web. Appl.Environ.Microbiol. 60(8):2677-2683, 1994

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The transfer of selenium between bacteria and the ciliated protozoan, Paramecium putrinum, was examined in laboratory cultures. The population growth of the ciliate was not inhibited in the presence of the highest concentrations of dissolved selenite or selenate tested (10(3) micrograms liter-1). Experiments with radioactive [75]selenite or [75]selenate indicated that accumulation of selenium by ciliates through time was low when feeding and metabolism were reduced by incubating at 0 degrees C. However, selenium accumulated in ciliate biomass during incubation with dissolved [75]Se and bacteria at 24 degrees C and also when bacteria prelabeled with [75]Se were offered as food in the absence of dissolved selenium. When [75]Se-labeled bacterial food was diluted by the addition of nonradioactive bacteria, the amount of selenite and selenate in ciliates decreased over time, indicating depuration by the ciliates. In longer-term (>5-day) fed-batch incubations with [75]selenite-labeled bacteria, the selenium concentration in ciliates equilibrated at approximately 1.4 micrograms of Se g(dry weight)-1. The selenium content of ciliates was similar to that of their bacterial food on a dry-weight basis. These data indicate that selenium uptake by this ciliate occurred primarily during feeding and that biomagnification of selenium did not occur in this simple food chain.