Streptomycininduzierte, reversible Vergilbung bei Chlamydomonas reinhardii

Abstract

The influence of streptomycin on grwoth, pigmentation and morphology of three mutants of the green alga Chlamydomonas reinhardii was investigated. 1. In the dark on solid media with sublethal doses of streptomycin both the streptomycin-sensitive strain and the streptomycin-resistant chromosomal mutant (isolated from the former strain) produce yellow colonies, whereas the uniparental resistant mutant grows green. With chloramphenicol under the same conditions no formation of yellow colonies is observed. 2. The streptomycin-induced loss of chlorophyll is accompanied by an almost complete loss of the thylakoid-structure. However, in the remaining chloroplast membrane starch grains and eye-spot are still present. 3. Yellow cells are able to produce under various conditions within 70–100 h green cultures containing normal chloroplasts. 4. In yellow cells the carotenoid/chlorophyll ratio is greatly enhanced. In the presence of streptomycin a general decrease of the pigment content is observed, while the relative amounts of the individual carotenoids and chlorophylls remain constant. 5. Streptomycin concentrations above the resistance level are found to be inhibitory for growth but not lethal. If, under the influence of light the streptomycin content of the medium decreases, green colonies are produced. The average lifetime of these colonies is shorter than that of uninhibited cultures. 6. The participation in thylakoid membrane formation of the different protein synthesizing systems of the cell is diseussed.