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PresentationsArchitecture of condensed DNA in bacteriaSemenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, 119991, Moscow, Kosygina 4, Tel.: (495) 939 73 00, e-mail: yufk@chph.ras.ru 1FRC Fundamentals of Biotechnology, RAS, Moscow, Russia. 2Faculty of Biology, Moscow State University M.V. Lomonosov, Moscow, Russia. The 3D architecture of the genome determines the function of the cell. The study of DNA condensation in a cell is important for understanding the mechanisms of bacterial survival and for medicine, since ordered DNA condensation ensures the resistance of pathogenic bacteria to the action of antibiotics. In a diluted solution, the DNA is several centimeters long. The length of the Escherichia coli bacteria is about 0.5 μ. Such a dramatic decrease in the volume occupied by DNA is a consequence of its condensation. It was found that DNA is organized hierarchically in the nucleoid with three levels of DNA compaction: the lower level (small scale ≥ 1 kbp) is provided by histone-like NAP proteins. Under the stress of starvation, bacteria, in contrast to actively growing bacteria, use an energy-free mechanism to maintain order and protect vital structures (DNA), as in inanimate nature. The study of the structure of DNA in the nucleoid of the bacterium Escherichia coli was carried out using diffraction of synchrotron radiation and transmission electron microscopy (TEM). The experimental results made it possible to visualize the structures of the lower hierarchical level of DNA compaction in the nucleoid of dormant cells. For the first time, a series of diffraction experiments carried out indicates the presence of a periodic ordered organization of DNA in all studied bacteria. TEM made it possible to visualize the information about the type of DNA condensation in the nucleoid of the bacterium Escherichia coli. Intracellular nanocrystalline, liquid crystal and folded nucleosome-like DNA structures were found. A folded nucleosome-like structure was observed for the first time; it is the result of multiple folding of long DNA molecules around the Dps protein and its associates.
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