RESUMEN
It is known that antibiotics which have an effect on 70 S ribosomes inhibit both the bacterial and the mitochondrial protein synthesis of plants and animals. This also applies to the plastid protein synthesis of plants. On this basis the present study has examined whether the inhibition of the mitochondrial protein synthesis caused by such antibiotics, may also be recognized by structural changes in the mitochondria. The effects on the ultrastructure of plastids have been investigated comparatively. The mixotroph flagellate Chlamydomonas reinhardii was used in our study. It was found that gentamycin (0.3 to 0.6 microgram/ml) and lincomycin (200 and 300 microgram/ml) cause structural anomalies in the mitochondria and in the plastids as well. Depending on the concentrations and the periods of exposure the mitochondria exhibited the following alterations: disorientation of the cristae within the organelles, reduction in the number of cristae and considerable differences of their length. In addition, vesicles and bodies which are surrounded by circular single or doubled membranes appeared in the mitochondria under the influence of gentamycin. We were able to detect mitochondria of unusual sizes and shapes in the cross sections. We also noticed changes in the arrangement of the thylakoids in the plastids under the influence of both gentamycin and lincomycin. In addition, electron-dense thylakoids, the so-called compact membranes, appeared under the influence of gentamycin. We suspect that mitochondrial alterations under the influence of such antibiotics could be one of the causes of side-effects, which frequently occur in medical use.
