An assessment of arsenate selection as a method for obtaining nonphotosynthetic mutants of chlamydomonas.

It has been proposed that the absence of photosynthesis in Chlamydomonas reinhardii produces a relative arsenate resistance and that selection for arsenate resistance therefore serves as an enrichment for nonphotosynthetic mutants (Togasaki and Hudock 1972; Harris, Boynton and Gillham 1974). We have found that: 1. mutants selected for arsenate resistance are not substantially enriched for acetate-requiring mutants as compared with unselected cells; 2. none of the acetate-requiring mutants we obtained without arsenate selection are arsenate resistant; 3. the acetate-requiring mutants obtained following arsenate selection are all capable of CO(2) fixation, suggesting that they do not have a major lesion in primary photosynthetic processes; 4. in most acetate-requiring mutants selected on arsenate medium, the arsenate-resistant and acetate-requiring characters segregate from one another during meiosis, indicating that these two characters arose independently. We conclude that if any enrichment is provided by selecting for arsenate resistance, it is for only a subclass of acetate requirers that are not obviously defective in photosynthesis.