1. A micro-organism identified as a species of Pweudomona8 forms adaptive enzymes which oxidize a large number of polyols. The properties and specificities ofthe enzymes have been studied in cell-free extracts. They are diphosphopyridine nucleotide-linked dehydrogenases converting polyols into ketoses.2. Sorbitol and dulcitol induce L.he formation of galactitol dehydrogenase, which oxidizes dulcitol to D-tagatose and accounts for the oxidation of other fully hydroxylated polyols containing an L-threo configuration adjacent to a primary alcohol group.3. Dulcitol also induces the formation of a less stable enzyme (D-iditol dehydrogenase) which accounts for the oxidation of certain fully hydroxylated polyols containing a D-threo configuration adjacent to a primary alcohol group.4. A labile mannitol dehydrogenase occurs in the extracts of cells grown in media supplemented with sorbitol.I am greatly indebted to Professor N. L. Edson for suggesting this problem and for his invaluable advice and criticism throughout the course of this work.

1. Ribosomal RNA has been prepared by extracting tissues with a phenol-cresol mixture, and ribosomal RNA can be selectively precipitated with m-cresol. No rapidly labelled RNA was associated with this material. 2. However, if RNA and DNA are extracted with 4-aminosalicylate and phenol-cresol mixture and the nucleic acids precipitated, DNA, glycogen and s-RNA (transfer RNA) can be extracted with 3m-sodium acetate and in this case rapidly labelled RNA remains associated with the ribosomal RNA. 3. The ribosomal RNA is stable in the presence of concentrated salt solution and, although the secondary structure is lost by heating at 70 degrees in 10mm-sodium acetate, it can be re-formed in the presence of 200mm-sodium acetate. 4. The 28s and 18s components have been separated and their base compositions determined.

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1. Nucleic acids were released from Escherichia coli by lysing with tri-iso-propylnaphthalene sulphonate and 4-aminosalicylate and then extracting with a phenol-cresol mixture. 2. Nucleic acids were similarly released from Bacillus subtilis after initial treatment with lysozyme. 3. DNA was sedimented after careful precipitation with m-cresol or 2-butoxyethanol (0.1-0.12vol.) in the presence of 20% sodium benzoate. 4. Contaminating ribosomal RNA was removed by precipitation in the presence of 4m-sodium chloride or by extracting DNA with an acetate-butyrate mixture, in which RNA is insoluble. 5. The DNA from B. subtilis has a transforming ability of 0.3-0.6% for the tryptophan marker. 6. Ribosomal RNA was then precipitated with rapidly labelled RNA by the addition of an equal volume of 2-butoxyethanol. 7. There was good separation of the nucleic acids from protein and polysaccharides.