| Summary: | An attempt was made to gain an insight into the energy conservation process in Chlamydomonas reinhardii. This organism possesses both mitochondria and a chloroplast and so respiration and photosynthesis can be studied in the same cell. The growth of C.reinhardii under different trophic conditions was characterised. The sensitivity of the wild-type (wt+) strain to a wide range, of inhibitors was determined in order to select potentially useful inhibitors for the isolation of drug-resistant mutants. The effect of these inhibitors on energy conservation was determined using chloroplast preparations from pea (Pisum sativum) and the CW15+ (cell wall-1ess) strain of C.reinhardii. The reported modes of action of the triorganotins and alky1guanidines on photosynthetic energy conservation were confirmed and, in some cases, extended. Mutant strains of C.reinhardii, which are resistant to inhibitors of oxidativa and photosynthetic phosphorylation, may provide an insight into the energy conservation process. Drug-resistant strains ot C.reinhardii were isolated and divided into five major classes on the basis of their cross-resistance characteristics. The TP-8+ (triorganotin-resistant) mutant was specifically resistant to trimethy1tin and triethy1tin but more sensitive than the Wt+ strain to other inhibitors. The alkylguanidine and ethidium bromide-resistant mutants exhibited pleiotropic resistance patterns to other membrane-active inhibitors. The resistance phenotypes of all the mutant strains were inherited in a Mendelian fashion and were generally present under different trophic conditions. The resistance, in these mutants may be due to change(s) in one or more of the cell membranes but the exact locus of resistance was not, determined. However, the resistance of the EBr-6+ (ethidium bromide-resistant) strain may be due to reduced uptake of ethidium bromide. Attempts to localise the mode of resistance of the TP-8+ strain at the sub-cellular level were unsuccessful.
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