Suit, Joan C. (The University of Texas M. D. Anderson Hospital and Tumor Institute, Houston). Ribonucleic acid in a "membrane" fraction of Escherichia coli and its relation to cell-wall synthesis. J. Bacteriol. 84:1061-1070. 1962.-A small amount of ribonucleic acid (RNA) was found in a "membrane" fraction prepared from osmotically sensitized Escherichia coli. It exhibited an elevated metabolic activity in that it attained the highest specific activity of any RNA in subcellular fractions of logarithmic-phase cells or spheroplasts prepared from logarithmic-phase cells which had been allowed to incorporate P(32) briefly. The metabolic activity of this RNA, in terms of P(32) incorporation, was found to be independent of cell-wall synthesis in the diaminopimelic acid (DAP)-less mutant, E. coli W 173-25, but was inhibited by penicillin in both this strain and in E. coli B. The latter effect is considered to be a result of other complex inhibitions of cellular metabolism by the antibiotic. The development of sensitivity to osmotic shock, capability of recovery, and synthesis of macromolecules in penicillin-treated and DAP-starved cultures, under these conditions, is described.