Dynamics of Macro- and Supramolecular Structures in the Bacterial Cytoplasm

The bacterial cytoplasm is increasingly recognized as a dynamic, out-of-equilibrium environment in which biochemical reactions occur. Here, we discuss recent advances in our understanding of the generation of microscopic forces in the cytoplasm, particle dynamics, and spatial compartmentalization. Mounting evidence supports the opinion that the cytoplasm is fluidized by active forces generated by stochastic, energy-dependent interactions between metabolites and macromolecules. The forces promote protein mobility, conformational transitions, and biochemical interactions, thereby enhancing intracellular coordination. Bacterial cytoplasmic dynamics are best understood as an emergent property of collective, non-equilibrium processes, providing a unifying framework for intracellular organization and function and redefining the physical basis of bacterial cell biology. We explain how the excitation of nano- and macromolecules in the cytoplasm generates an out-of-equilibrium force that changes the cytoplasm from a glass-like to a semi-liquid phase. We critically evaluate proposed drivers of cytoplasmic fluidity, including nucleoid-associated processes and non-equilibrium active forces.