title: Cadmium sensitivity, uptake, subcellular distribution and thiol induction in a marine diatom: exposure to cadmium.
abstract: The aims of this study were to (1) evaluate the changes in the Cd tolerance of a marine diatom after exposure under different Cd concentrations for various durations and (2) to explore the potential subcellular and biochemical mechanisms underlying these changes. The 72-h toxicity, short-term Cd uptake, subcellular Cd distribution, as well as the synthesis of phytochelatins (PCs) were measured in a marine diatom Thalassiosira nordenskioeldii after exposure to a range of free Cd ion concentrations ([Cd(2+)], 0.01-84nM) for 1-15 days. Surprisingly, the diatoms did not acquire higher resistance to Cd after exposure; instead their sensitivity to Cd increased with a higher exposed [Cd(2+)] and a longer exposure period. The underlying mechanisms could be traced to the responses of Cd cellular accumulation and the intrinsic detoxification ability of the preconditioned diatoms. Generally, exposure to a higher [Cd(2+)] and for a longer period increased the Cd uptake rate, cellular accumulation, as well as the Cd concentration in metal-sensitive fraction (MSF) in these diatoms. In contrast, although PCs were induced by the environmental Cd stress (with PC(2) being the most affected), the increased intracellular Cd to PC-SH ratio implied that the PCs' detoxification ability had reduced after Cd exposure. All these responses resulted in an elevated Cd sensitivity as exposed [Cd(2+)] and duration increased. This study shows that the physiological/biochemical and kinetic responses of phytoplankton upon metal exposure deserve further investigation.
authors.affiliation: State Key Laboratory in Marine Pollution, Section of Marine Ecology and Biotechnology, Division of Life Science, The Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Meng-Jiao
authors.initials: MJ
authors.lastname: Wang
authors.forename: Wen-Xiong
authors.initials: WX
authors.lastname: Wang
mesh_terms: D002104:Cadmium / Q000378:metabolism / Q000493:pharmacokinetics* / Q000633:toxicity*; D017377:Diatoms / Q000187:drug effects* / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D054811:Phytochelatins / Q000096:biosynthesis / Q000378:metabolism; D010940:Plant Proteins / Q000096:biosynthesis; D013347:Subcellular Fractions; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000493:pharmacokinetics / Q000633:toxicity
chemical_list: D010940:Plant Proteins; D013438:Sulfhydryl Compounds; D014874:Water Pollutants, Chemical; D002104:Cadmium; D054811:Phytochelatins; D005978:Glutathione