The distribution of ribosomal ribonucleic acids among subcellular fractions from bacteria and the adverse effect of the membrane fraction on the stability of ribosomes.

1. The distributions of nucleic acids and protein among fractions obtained by differential centrifugation from species of Pseudomonas, Aerobacter, Escherichia, Proteus and Bacillus have been studied. 2. The DNA in a cell wall-membrane fraction obtained by low-speed centrifugation from the Gram-negative species could be removed by homogenizing and subsequent washing. About 7-14% of the total RNA remained firmly attached and resembled ribosomal RNA in base composition. A similar fraction from the Gram-positive B. subtilis contained about one-half of the total bacterial DNA and only 60% of this could be removed by homogenizing and subsequent washing. 3. A deposit obtained by high-speed centrifugation could be separated into a heavy ribosome layer and a light turbid layer. In E. coli B the latter contained about equal concentrations of RNA and DNA and accounted for about one-half of the total bacterial NADP-activated 6-phosphogluconate dehydrogenase. 4. The washed cell wall-membrane fraction from most species accelerated the degradation of ribosomes. In Pr. vulgaris the activity of this fraction was exceptionally high and resulted in the progressive degradation of ribosomes during their isolation from this species. 5. A possible connexion between ribosome degradation and the synthesis of flagella is discussed in the light of these results.