Genetics of Bacterial Ribosomes

Abstract

INTRODUCTION
For an organelle as complex as the ribosome, genetic studies can play an important role in providing information about the components, how they are put together, and how synthesis and assembly may be controlled. Bacterial mutants with altered ribosomes, in spite of their scarcity, have proved to be of considerable utility in the study of ribosome structure and functions. Since the state of our knowledge in this field has been reviewed recently (Davies and Nomura 1972), this chapter will summarize recent work in the context of earlier findings. In addition, information on many mutations related to ribosomes is compiled in Table 1.

ORGANIZATION OF rRNA STRUCTURAL GENES
Evidence for 16S + 23S rRNA Transcriptional Units
Analysis of the residual rRNA synthesis after inhibition with rifampicin (Pato and von Meyenberg 1970; Doolittle and Pace 1970, 1971; Bremer and Berry 1971), the reinitiation of rRNA synthesis following amino acid starvation of stringent cells (Kossman, Stamato and Pettijohn 1971), and hybridization of rRNA with DNA fragments from B. subtilis (Colli, Smith and Oishi 1971; Colli and Oishi 1969) have indicated that rRNA genes in bacteria are organized into transcriptional units containing one gene for each type of rRNA, with the gene order 16S–23S–5S. Electron microscopic observations of DNA in the process of being transcribed are consistent with these conclusions (Miller and Hamkalo 1972). Several recent observations have provided more direct evidence for 16S + 23S rRNA transcriptional units. On the other hand, direct evidence of the inclusion of 5S rRNA...