The discontinuous and scrambled organization of the small subunit and large subunit rRNA coding regions in Chlamydomonas mitochondrial DNA has been well documented. Our goals were to demonstrate that the small transcripts produced by these coding regions in Chlamydomonas eugametos are assembled into mitochondrial ribosomes and to characterize the sedimentation properties of these ribosomes and their subunits in sucrose gradients. Putative mitochondrial ribosomes (60–66S) and their large (44–50S) and small (35–39S) subunits were identified by slot blot hybridization which sedimented independently of the chloroplast and cytosolic ribosomes. A crude mitochondrial pellet prepared from C. eugametos was enriched for mitochondrial small subunit and large subunit rRNA subfragments thereby providing independent confirmation of the mitochondrial association of these rRNA molecules.
