Cell wall composition affects Cd 2+ accumulation and intracellular thiol peptides in marine red algae

Abstract

Two red macroalgae species, Gracilaria cornea and Chondrophycus poiteaui, were evaluated for their intra and extracellular Cd 2+ accumulation capacity, photosynthetic response and thiol peptide production. Algae were exposed for 3 and 7 days to 0.1 and 1 μg CdCl 2 ml −1 (0.89 and 8.9 μM). Intracellular accumulation of Cd 2+ by G. cornea was relatively low, only comprising 20% of total metal (intracellular + extracellular). In contrast, C. poiteaui accumulated intracellularly close to 100% of total Cd 2+. In both species, metal uptake was dependent on the external Cd 2+ concentration, metal exposure time and cell wall composition. In response to Cd 2+ exposure, low amounts of thiol peptides were synthesized and the major difference between G. cornea and C. poiteaui was in the cell wall composition. The absence of insoluble polysaccharides in the cell wall of C. poiteaui suggested that this insoluble fraction might be involved in establishing an efficient barrier for the intracellular accumulation of Cd 2+. This is the first study in which the cell wall composition, its influence on Cd 2+ accumulation and intracellular responses in red macroalgae are evaluated.