Abstract
HDC-TEM has opened a way to visualize the ultrastructure of ice embedded whole cells. The extraordinary advantage of this technique is that it exhibits structures close to the living state while retaining all the in vivo molecular constituents undisturbed. We attempted to identify in vivo DNA by incorporation of BrdU, which conferred electron density to newly synthesized DNA in ice embedded cyanobacterial cells. Localization of Br in the electron dense area in the identical cell was investigated by electron spectroscopic imaging (ESI). Br was also appeared to be associated with polyphosphate bodies, which would indicate a close relationship between newly synthesized DNA and polyphosphate bodies. While ESI indicates the DNA localization, high resolution HDC-TEM reveals the fine fibrous structures in situ. The combination of ESI with HDC-TEM will be extremely useful to study the in vivo dynamics of DNA synthesis, and its structural and conformational changes close to the living state at high resolution.
