Accumulation of arsenic in a unicellular alga Chlamydomonas reinhardtii

The unicellular alga Chlamydomonas reinhardtii accumulated and biomethylate d arsenic efficiently, A wall-less cell strain (CW-15) of Chlamydomonas rei nhardtii proliferated in a low level arsenic-containing medium (0.01-0.1 mm ol dm(-3)) more than that in an arsenic-free medium. Although the growth of the algal cells was only slightly more inhibited in a growth medium contai ning arsenic at a concentration of 1.0 mmol dm(-3) than that in an arsenic- free medium, it was completely inhibited at concentrations of 10 and 100 mm ol dm(-3). Furthermore, transformed strains were obtained by random introdu ction of plasmid pJD67, carrying an Arg(+) gene, into a wall-less cell Arg( -) mutant CC425 strain. Finally we selected a strain, named AS1, among the transformed CC425 of the arsenic-sensitive group. The accumulation of arsen ic by the AS1 strain was about three-fold higher than that by the CW-15 str ain and 80-90% of the inorganic arsenic was transformed into a dimethylarse nic compound. It is suggested that the AS1 strain is a suitable model for i nvestigation of the accumulation and biomethylation of arsenic by microalga e in freshwater environments. Copyright (C) 1999 John Wiley & Sons, Ltd.