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1. The distribution of ribosomal particles between the soluble and membrane fractions of exponential-phase cells of Bacillus licheniformis was studied. The cells were very gently lysed by a combined treatment with lysozyme and Brij 58 in 10 mM. Tris-buffer, pH 7.6, with 60 mM K+, 10 mM Mg2+, 0.5 mM spermine and 0.75 mM spermidine. The proportion of the ribosomal material present in the membrane fraction was estimated after solubilization of the membranes by the combined action of Brij 58, deoxyribonuclease and lipase. 2. Under these conditions of lysis 96% of the total ribosomal material, consisting of subunits (12%) monosomes (20%) and polyribosomes (68%) and most of the cellular DNA, is found to be membrane-bound. 3. In the soluble fraction, containing only 4% of the total cellular amount of the ribosomal material, only subunits and 70S particles and no polyribosomes are found. 4. DNA does not seem to be involved in the binding of the ribosomal material to the membranes. 5. The results will be discussed considering the question of whether the distribution described in this paper represents the true distribution in vivo of ribosomes. [ABSTRACT FROM AUTHOR]

1. A study of sensitivity to T1 ribonuclease of the 16 S and 23 S RNAs within the 30 S and 50 S subunits and the 70 S ribosomes from Escherichia coli has been performed using sucrose gradient sedimentation. 2. The sensitivity of 23 S RNA within the 50 S subunits is greater than that of 16 S RNA within the 30 S subunits. 3. After action of T1 ribonuclease on both 30 S and 50 S subunits, under conditions which would lead to total hydrolysis of the free RNAs, the persistence of protected RNA fragments of large size is observed. 4. A much less significant degradation of 16 S and 23 S RNAs is observed, when T1 ribonuclease action is performed under the same conditions upon the 70 S ribosomes, instead of 30 and 50 S subunits; this supports the existence of regions m both RNAs involved in the association of the two subunits. [ABSTRACT FROM AUTHOR]