  Recent experiments have revealed that cytoplasms become glassy when their
metabolism is suppressed, while they maintain fluidity in a living state. The
mechanism of this active fluidization is not clear, especially for bacterial
cytoplasms, since they lack traditional motor proteins, which can cause
directed motions. We introduce a model of bacterial cytoplasm focusing on the
impact of conformational change in proteins due to metabolism. In the model,
proteins are treated as particles under thermal agitation, and conformation
changes are treated as changes in particle volume. Simulations revealed that a
small change in volume fluidizes the glassy state, accompanied by a change in
fragility, as observed experimentally.
