Removal, accumulation and resistance to chromium in heterotrophic Euglena gracilis

► The protist Euglena gracilis has the ability to accumulate large amounts of chromium, particularly Cr(III). ► The Cr(III) toxicity depends on the medium composition, becoming high in the absence of carboxylic acids. ► There are increased activities of both particulate and soluble chromate reductase activities in response to the oxidative stress induced by Cr(VI) or Cr(III). ► Large secretion of malate, as well as enhanced intracellular contents of ascorbate and thiol-molecules are also part of the chromium resistance mechanisms in this protist.