Release of Biologically Active Peptides from Escherichia coli at Subzero Temperatures1

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Moss, C. Wayne (North Carolina State University, Raleigh), and M. L. Speck. Release of biologically active peptides from Escherichia coli at subzero temperatures. J. Bacteriol. 91:1105–1111. 1966.—Freezing and storage of Escherichia coli at −20 C in phosphate buffer resulted in loss of cell viability and a pronounced leakage of cellular material which had maximal absorption at 260 mμ. Greater loss in cell viability occurred when cells were frozen in distilled water, but only small amounts of 260 mμ absorbing material were detected. Unfrozen cells stored at 2 and 22 C in each menstruum showed little loss in viability, but cells in phosphate buffer released significant amounts of material during storage. Leakage material from cells in phosphate buffer contained greater amounts of ribonucleic acid and amino acids than did material from cells in distilled water. Leakage material from frozen cells contained protein in the form of peptides of relatively small molecular weight; this was not observed for unfrozen cells. These compounds protected a dilute cell suspension from the lethal effects of freezing, and also possessed biological activity for the recovery of cells which had been “injured” by freezing. Direct cell counts indicated that the material released was not a result of cell lysis.

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