Concentrations of phytochelatins and glutathione found in natural assemblages of seaweeds depend on species and metal concentrations of the habitat.

The occurrence of the metal-complexing thiol peptides, phytochelatins (PC) in natural populations of brown, red and green seaweeds (marine macroalgae) was studied. Concentrations of PCs and their precursor glutathione (GSH) were measured in seaweeds collected from locations in south-west England with different levels of contamination by trace metals, to evaluate their role under natural environmental conditions. The non-protein thiols were identified and quantified in seaweed extracts by HPLC and the molecular structures of PCs were confirmed by LC-ESIMS. The capacity for production of PCs of representative seaweeds under Cd and Zn exposure was also assessed, experimentally. The concentrations of metals/metalloids (As, Cu, Cd, Pb and Zn) accumulated by the seaweeds were determined by ICP-MS. For the first time, PCs are reported in native Phaeophyceae (Fucus spp.), Rhodophyceae (Solieria chordalis) and Chlorophyceae (Rhizoclonium tortuosum) but not in thalli of Ulva spp. and Codium fragile (Chlorophyceae). The concentrations of PCs in brown and red seaweeds correlated with the contamination history of sampling sites and total metal burden of thalli. The highest concentrations of metals (5.6-7.1micromolg(-1) DW), PCs (200-240nmolSHg(-1)DW) and GSH (1,550-3,960nmolSHg(-1)DW), and the longest PC chain lengths (PC(2-4)) were found in Fucus spp. collected from the most contaminated site. A combination of PC-production and maintenance of high concentrations of GSH allows Fucus spp. and R. tortuosum (2,000nmolGSHg(-1)DW) to thrive in highly contaminated environments whereas in Ulva spp. high concentrations of GSH (1,000-1,500nmolSHg(-1)DW) together with thick cells walls and a high polysaccharide content appear to be responsible for metal-resistance. The lack of production of PCs in these green macroalgae suggests lower intracellular metal accumulation rather than an inability for synthesizing PCs. The higher concentrations of Cu (approximately 3.4micromolg(-1)DW) found in thallus of S. chordalis, compared with the Fucus spp. (1.5-2.4micromolg(-1)DW) from the same site, may induce stronger oxidative stress and result in lower concentrations of reduced glutathione (648nmolSHg(-1)DW) and PCs (70nmolSHg(-1)DW). As a consequence S. chordalis at this site may have a lower resistance to metals and a more restricted distribution than the fucoids. Both fucoid species and the red seaweed Gracilaria gracilis, but not Ulva spp. or C. fragile, from low contaminated sites synthesized PCs under laboratory conditions when exposed to very high concentration of Cd. Our results clearly show that natural assemblages of seaweeds, belonging to disparate phylogenetic groups produce PCs when exposed to a mixture of metals in their environment. However, the involvement of thiol peptides in metal homeostasis, detoxification and resistance varies between seaweed species that are growing under the same environmental conditions.

Uptake of cadmium ions in white-rot fungus Trametes versicolor: effect of cd (II) ions on the activity of laccase.

The effects of cadmium Cd (II) ions on the physiology and biological activity of Trametes versicolor, a strain belonging to white-rotting Basidiomycetes, were examined. Cd (II) ions were added to 10-day-old cultures grown on a liquid medium, or at the time of inoculation. Our experiments showed that T. versicolor is a good cadmium biosorbent from aqueous solution, this strain removing almost all the Cd (ll) ions over the first 2h of incubation by what appears to be a rapid, energy-independent surface binding phenomenon, at the rate of approximately 2mg Cd per g mycelial dry weight. An additional slower and energy-dependent transport mechanism was also present, taking in approximately 0.3mg Cd (II) perg dry weight. It is also shown that these Cd (II) ions significantly stimulate the activity of extracellular laccase when added to 10-day-old cultures.