  Electron microscopy and X-ray diffraction studies of dormant E. coli cells
revealed several forms of nucleoid condensation: quasi - nanocrystalline, quasi
-liquid crystalline (or spore-like) and folded nucleosome - like structure. Of
particular interest is the third type of structure since it was described here
for the first time: the folded nucleosome-like. Such a structure has no
relation to the toroidal DNA organization, which are the intermediate form in
the formation of the quasi - nanocrystalline structure. Results observed here
shed a new light both on the phenomenon of nucleoid condensation in prokaryotic
cells and on the general problem of developing a response to stress. It was
found out that there is no single mechanism for nucleoid condensation in the
population of a dormant cell; diversity in their number, shape and packing has
been seen. According to the recognized concept of a bacterial population as a
multicellular organism, its heterogeneity allows to respond flexibly to the
environmental changes and to survive in stressful situations. That is the
reason why we observed at least three types of nucleoid condensation in dormant
E. coli cells. Heterogeneity of dormant cells increases the ability of the
whole population to survive under various stress conditions. For better
understanding of the nucleoid condensation mechanism, it is necessary to study
the reverse transition of the nucleoid in bacteria from the dormant to the
functional state.
