Abstract
In preliminary experiments, we have applied the ultrathin frozen-sectioning technique to the immunoelectron microscopic labeling of DNA in procaryotic cells. In addition to two anti-DNA antibodies that immunolabeled total DNA, we used an anti-bromodeoxyuridine (BrdUrd) antibody that specifically detected the BrdUrd that was newly incorporated into the DNA of a thymine auxotroph that was deprived of thymine and then pulsed with BrdUrd. The immunolabeling of the incorporated BrdUrd was largely confined to the cell periphery, whereas the labeling of the bulk of the DNA was largely interior. These results are briefly discussed.
