Condensation of nucleoid in Escherichia coli cell as a result of prolonged starvation

Abstract: 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.