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Structure and function of cytoplasmic organelles in transiently and permanently bleached Euglena

1973; Elsevier BV; Volume: 78; Issue: 1 Linguagem: Inglês

10.1016/0014-4827(73)90043-8

1090-2422

B. van Pel, R. Bronchart, Florence Kebers, C. Cocito,

Microbial Community Ecology and Physiology

Abstract Virginiamycin is an antibiotic composed of two synergistic factors, M and S, which stop growth and protein synthesis in procaryotic cells. The two virginiamycin components, separately and in combination, do not alter the multiplication of algae in heterotrophic media. However, virginiamycin M inhibits chlorophyll formation, and virginiamycin S, which alone has no apparent effect, increases this inhibitory action of M. Virginiamycin M produces bleaching of Euglena gracilis : this phenotypic change is temporary in the absence of S, but permanent if S is present. Characteristic alterations of chloroplast structure occur in the presence of virginiamycin M: disappearance of the pyrenoid, and appearance of free-thylakoids. In the presence of both virginiamycins, chloroplasts loose their spindle shape and their lamellar systems, and are converted into reticulated bodies. There is, thus, a relationship between morphological, biochemical and genetic alterations of the chloroplasts. On the other hand, mitochondria from virginiamycin-treated cells appear intact. The reason for such difference between chloroplasts and mitochondria is unknown. A theory explaining the induction of cytoplasmic mutants by protein inhibitors is proposed. The action of virginiamycin on chloroplast ribosomes and RNA is analysed in [34].