Mutants in Escherichia coli ribosomes: a new selection.

Only a few ribosome genes have been identified. Increasing the available kinds of ribosome mutants would thus facilitate the analysis of specification and function of the organelle. In an attempt to reveal a number of ribosome genes, we sought mutants that could not form functional ribosomes at a nonpermissive temperature (43 degrees ). Cells were depleted of ribosomes by nutrient starvation at 43 degrees , and 98 strains that could not recover from the starvation were then isolated. Of these 98, many satisfied auxiliary criteria for ribosome mutants; 23 showed increased sensitivity to antibiotics that affect ribosome function; and 8 of 20 representative strains had crude extracts more temperature sensitive than that of the parental strain when assayed for polyphenylalanine formation in the presence of excess soluble enzymes (S100) of the parental strain. In further tests with two of these strains, the temperature sensitivity of the washed ribosomes, compared to that of the parental strain, was confirmed. The variety of phenotypes among the mutants suggests that this selection is capable of revealing mutants in many ribosome genes.