Department of Structure of Matter, Semenov Federal Research Center of Chemical Physics, RAS, Moscow, Russia.
Department of Microbiology, Federal Research Center 'Fundamentals of Biotechnology' RAS, Moscow, Russia.
PLoS One. 2020 Oct 2;15(10):e0231562. doi: 10.1371/journal.pone.0231562. eCollection 2020.
One of the adaptive strategies for the constantly changing conditions of the environment utilized in bacterial cells involves the condensation of DNA in complex with the DNA-binding protein, Dps. With the use of electron microscopy and electron tomography, we observed several morphologically different types of DNA condensation in dormant Escherichia coli cells, namely: nanocrystalline, liquid crystalline, and the folded nucleosome-like. We confirmed the presence of both Dps and DNA in all of the ordered structures using EDX analysis. The comparison of EDX spectra obtained for the three different ordered structures revealed that in nanocrystalline formation the majority of the Dps protein is tightly bound to nucleoid DNA. The dps-null cells contained only one type of condensed DNA structure, liquid crystalline, thus, differing from those with Dps. The results obtained here shed some light on the phenomenon of DNA condensation in dormant prokaryotic cells and on the general problem of developing a response to stress. We demonstrated that the population of dormant cells is structurally heterogeneous, allowing them to respond flexibly to environmental changes. It increases the ability of the whole bacterial population to survive under extreme stress conditions.
细菌细胞利用一种适应不断变化的环境条件的策略是将 DNA 与 DNA 结合蛋白 Dps 凝结在一起。通过使用电子显微镜和电子断层扫描，我们在休眠的大肠杆菌细胞中观察到几种形态上不同的 DNA 凝结类型，即纳米结晶、液晶和折叠核小体样。我们使用 EDX 分析证实了所有有序结构中都存在 Dps 和 DNA。对三种不同有序结构的 EDX 光谱进行比较表明，在纳米结晶形成中，大多数 Dps 蛋白与核质 DNA 紧密结合。 dps 缺失细胞只含有一种凝结的 DNA 结构，即液晶，因此与含有 Dps 的细胞不同。这里获得的结果揭示了休眠原核细胞中 DNA 凝结的现象以及对压力作出反应的普遍问题。我们证明休眠细胞群体在结构上是异构的，使它们能够灵活地对环境变化作出反应。这增加了整个细菌群体在极端压力条件下生存的能力。
