ИСТИНА

One of the strategies implemented in bacterial cells is related to the protection of the nucleoid from unfavourable environmental conditions by binding of DNA to specific histone-like proteins, the main one being the protein Dps (DNA binding protein from starved cells), and condensation of DNA with DPS in nanocrystalline complex which was recently discovered in gram-negative bacteria E.coli that are subject to 48-hour starvation [1]. Nanocrystallization (or biocrystallization) of nucleoid helps to protect the nucleoid from damage and resume the activity of the bacterial cells later, upon improvement of the external conditions. Thus, in the bacteria E. coli after 48 hours of starvation, the nucleoid together with a stress-induced protein Dps forms highly ordered, tightly packed DNA–Dps co-crystals [1]. The structure of these crystals within a cell was studied using cryoelectron microscopy and tomography [1], as well as by use of synchrotron radiation on macromolecular crystallography station ID-23-1[1]. However, the DNA conformation within these complexes has remained unsolved. One of the reasons why it was difficult to solve the conformation is the small size of the nanocrystals of the nucleoid within a cell  400 nm. We expect that with the use of the XFEL radiation we can obtain further structural information and our ultimate target is the crystallographic data to 2.5 Å resolution. Fresh (48 hours of starvation) sample usually contain 10 9 cells/ ml. We have not yet tried to isolate the crystals after cell lysis by gradual centrifugation. However, we are confident that we can perform such sample preparation