[Electron microscopic study of the nuclear transformations 05 E. coli K12S and K12S (lambda 26) after irradiation with ultraviolet rays and x-rays].

Nuclear transformations induced in E. coli K12S and K12S(lambda(26)) by ultraviolet radiations and x-rays have been studied with ultrathin sections in the electron microscope. The nucleoplasm keeps its normal aspect during "fragmentation" and during "condensation" of the nucleus into the "vesicular" form. Serial sections show that the "fragmented" nucleus consists in reality of only one very tortuous vacuole. No difference either in the shape or in the fine structure of the nucleus could be observed between the lysogenic strain and the non-lysogenic strain. A high concentration of NaCl has a "condensation" effect on the fragmented nuclei and decreases the induction rate.