We report our measurements of the dynamics of H-NS proteins, which interact with both proteins and DNA simultaneously, in live E. coli bacteria. The dynamics turn out to differ significantly from other molecules reported previously. A new power-law distribution was observed for the diffusion coefficients of individual H-NS proteins. In addition, we observed a new distribution of displacements, which does not follow the Gaussian, Cauchy, or Laplace distributions, but the Pearson Type VII distribution. Furthermore, we experimentally measured, for the first time, the time/frequency dependence of the complex modulus of the bacterial cytoplasm, which deviates from the viscoelasticity of homogeneous protein solutions and shows a glass-liquid transition. Lastly, we observed that the dynamics of H-NS protein is cell-length/cell-age dependent. The findings are expected to fundamentally change the current views on bacterial cytoplasm and diffusional dynamics of molecules in bacteria. DNA binding are crucial for the biological activities of 59 H-NS proteins [17]. 60 In this work, we present our results on the dynamics 61 of H-NS proteins in live Escherichia coli (E. coli) bac-62 teria, which shows unique behaviors compared to other 63 molecules reported previously. We observed a new power-64 law distribution of the diffusion coefficients of individual 65 H-NS proteins and a new distribution of displacements 66 that does not follow the Gaussian, Cauchy, or Laplace 67 distributions, but the Pearson Type VII distribution. 68 More importantly, for the first time, we experimentally 69 measured the time/frequency dependence of the complex 70 modulus of the bacterial cytoplasm, which deviates from 71 the viscoelasticity of homogeneous protein solutions and 72 shows a glass-liquid transition. Finally, we found that 73 the dynamics of H-NS protein is dependent on cell-age. 74 The findings are expected to fundamentally change the 75 current views on bacterial cytoplasm and diffusional dy-76 namics of molecules in bacteria. 77 II. METHODS AND MATERIALS 78 A. Bacterial strain, growth, and sample 79 preparation 80 A K12-derived E. coli strain (a gift from [19]) was 81 used in this study. This strain expresses H-NS proteins 82 fused to mEos3.2 fluorescent proteins [19, 20]. The bac-83 terial strain was grown at 37 • C overnight in defined M9 84 minimal medium, supplemented with 1% glucose, 0.1% 85 casamino acids, 0.01% thiamine and appropriate antibi-157 coefficient D = (8.0 ± 0.3) × 10 3 nm 2 /s α and the anoma-158 lous scaling exponent α = 0.57 ± 0.02. It is noted that 159 the unit of the generalized apparent diffusion coefficient 160 D contains the anomalous scaling exponent α. Alterna-235 comparison and statistics on the generalized diffusion co-236 efficient D is not stringent because 1) the unit of D con-237 tains the anomalous exponent α, and 2) the fitted α is 238 different for different individual MSD curves. To address 239 this concern, we calculated the short-time apparent dif-240 fusion coefficient D s , which has a unit of n...