Isolation, growth, ultrastructure, and metal tolerance of the green alga, Chlamydomonas acidophila (Chlorophyta)

An acidophilic volvocine flagellate, Chlamydomonas acidophila (Volvocales) that was isolated from an acid lake, Katanuma, in Miyagi prefecture, Japan was studied for growth, ultrastructural characterization, and metal tolerance. Chlamydomonas acidophila is obligately photoautotrophic, and did not grow in the cultures containing acetate or citrate even in the light. The optimum pH for growth was 3.5-4.5. To characterize metal tolerance, the toxic effects of Cd, Co, Cu, and Zn on this alga were also studied. Effective metal concentrations, which limited the growth by 50%, EC50 were measured, after 72 h of static exposure. EC(50)s were 14.4 mum Cd2+, 81.3 mum Co2+, 141 mum, Cu2+, and 1.16 mum Zn2+ for 72 h of exposure. Thus, this alga had stronger tolerance to these metals than other species in the genus Chlamydomonas.