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Abstract
SUMMARY: Alter ultraviolet irradiation, the growth of Escherichia coli (non-lysogenic and lysogenic for phage λ) resulted in diminution of the 8S component of water extracts of the bacteria and the loss of its characteristic spike. In the induced lysogenic bacteria, 8S material was synthesized in the second half of the latent period and the characteristic shape of the boundary was regained. The 8S material was free DNA of relatively high molecular weight and these changes were correlated with alterations in the rate of DNA synthesis in the irradiated bacteria. The synthesis of ribosomal material was found to continue during the development of phage λ. After log phase bacteria had stood for a short time in saline, extracts prepared in tris buffer+0·01 m-magnesium acetate showed that an 85S component developed. The latter was replaced by slower material (73S) when the bacteria (non-lysogenic and lysogenic, irradiated or unirradiated) resumed logarithmic growth in broth. This conversion may reflect a configurational change in the 73 S component in environments which do not support growth.
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