Cadmium Accumulation Kinetics in Rhodococcus jostii RHA1 and Potential Effects of Brominated Flame Retardants

摘要

We studied ethylenediaminetetraacetate (EDTA), nitrilotriacetate (NTA), and citrate effects on Cd uptake by the bacterium Rhodococcus jostii RHA1. Possible influences of two brominated flame retardants (BFRs), tetrabromobisphenol A (TBBPA) and 4-monobromodiphenyl ether (BDE-3), on Cd accumulation were also investigated. Cd uptake followed the one-binding site Michaelis-Menten equation without the presence of organic ligands. Nevertheless, EDTA and NTA induced Cd uptake due to the formation of ternary complexes on the cell surface. The most remarkable induction of Cd uptake was observed in the citrate-addition experiment because of the direct internalization of Cd-citrate complex. In contrast to EDTA, NTA, and citrate, both BFRs had no effects on Cd uptake and efflux unless notable toxicity was observed. Overall, our results suggest that Cd accumulation kinetics in RHA1 did not comply with the free ion activity or biotic ligand model. Whether this phenomenon can be extended to other bacteria needs to be further examined.