The Localization of Deoxyribonucleic Acid in Escherichia coli

Abstract

Log-phase cultures of E. coli 15 T- grown in tritium-labeled thymidine were fixed in buffered 1% osmium tetroxide, followed by 10% formaldehyde, dehydrated in graded alcohols and embedded in n-butyl methacrylate. Sections 0.25 [mu] thick were cut on a Porter-Blum microtome and were radioauto-graphed using a stripping film technique. Localization of deoxyribonucleic acid (DNA) in the cells was estimated by studying the distribution of radioactivity in transverse serial sections of individual cells, and the distribution of photographic grains associated with individual sections. A comparison of the distribution obtained with electron micrographs of thin sections of cells prepared in the same manner showed that DNA was localized in the "nuclear region" described by several authors.