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Abstract
When Euglena gracilis is grown in the presence of some antibiotics (Provasoli, Hutner & Schatz, 1948 ; Ebringer, 1962, 1966 ; Celmer & Ebringer, 1967 ), organisms with no chloroplasts are soon produced. These aplastidic organisms can then be isolated and maintained as permanently colourless races. The mechanism of the bleaching action is still in dispute. We have suggested an interaction with plastid DNA or some hereditary apparatus responsible for chloroplast replication (Ebringer, Mego & Jurasek, 1969 ). To test this hypothesis, we have examined some antibacterial agents which inhibit DNA synthesis in bacteria or in other organisms. Nalidixic acid inhibits specifically the synthesis of DNA in bacteria (Goss, Deitz & Cook, 1965 a, b; Cook et al. 1966 ) and exerts a mutagenic effect upon proliferating bacteria (Cook, Goss & Deitz, 1966 ). Some other agents which affect DNA synthesis in bacteria also exert a bleaching action on Euglena gracilis (to be published), so the question arises whether nalidixic acid is able to produce permanent colourless races of this organism.
- Accepted:
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