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Abstract:
Bacterial lysis induced by the expression of the cloned lysis gene of the RNA bacteriophage MS2 in Escherichia coli was shown to be under the same regulatory control mechanisms as penicillin-induced lysis. It was controlled by the stringent response and showed the phenomenon of tolerance when E. coli was grown at pH 5. Changes in the fine structure of the murein were found to be the earliest physiological changes in the cell, taking place 10 min before the onset of cellular lysis and inhibition of murein synthesis. Both the average length of the glycan strands and, with a time lag, the degree of cross-linkage were altered, indicating that a lytic transglycosylase and a DD-endopeptidase had been triggered. After extensive separation of the membranes by isopycnic sucrose gradient centrifugation, the lysis protein was present predominantly in the cytoplasmic membrane and in a fraction of intermediate density and, to a lesser degree, in the outer membrane, irrespective of the conditions of growth. However, only under lysis-permissive conditions could a 17% increase in the number of adhesion sites between the inner and outer membranes be observed. Thus, a casual relationship between lysis and the formation of lysis protein-induced adhesion sites seems to exist.
