THE EFFECT OF X RAYS ON THE MACROMOLECULAR ORGANIZATION OF ESCHERICHIA COLI

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Abstract
The effects of X-irradiation on the structure of the macromolecular components of E. coli (B/r) were investigated with the analytical ultracentrifuge and by chemical analysis. Ex-posure to doses of X-rays sufficient to inactivate more than 99% of the cells does not change the component pattern observed in cell-free extracts if the cells are analyzed immediately following exposure. However, if the cells are incubated in a phosphate buffer-glucose soln. at 37[degree]C for 90 min. subsequent to irradia-tion, a marked decrease in several of the components of the cell-free extract is noted. In the absence of glucose, this decrease is not evident. The most striking changes are the disruption and disappearance of an enzymatically active ribonucleic acid containing a participate component with a sedimentation constant of 40 S, and a loss of a slower moving component reported to be free DNA.