The Atypical Ribosomal RNA Complement of Rhodopseudomonas spheroides

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Abstract
SUMMARY: Ribosomes and phenol-purified RNA were prepared from Rhodopseudomonas spheroides and were characterized by sucrose density-gradient centrifugation and sedimentation-velocity centrifugation. The ribosomes extracted from R. spheroides correspond to the 30S, 50S and 70S ribosomes derived from other bacteria. Under appropriate conditions polyribosomes were extracted. The primary ribosomal RNA of R. spheroides corresponds to the 16S particle of other bacteria. Rhodopseudomonas spheroides was devoid of the 23S ribosomal RNA typically found in other bacteria. Preparations of phenol-purified R. spheroides RNA contain, in addition to 16S RNA, smaller amounts of an RNA component which sediments more slowly than the 16S unit, with a sedimentation coefficient of about 14-15S. Of several other Athiorhodaceae examined, only Rhodopseudomonas capsulata had an unusual RNA complement like that of R. spheroides.