Nonlinearity in cytoplasm viscosity can generate an essential symmetry breaking in cellular behaviors

- Protoplasmic flow in a giant ameboid cell is modeled and the impact of nonlinearity in viscosity on its behaviors is considered.
- The nonlinearity in the viscosity generates a novel type of symmetry breaking in the protoplasmic flow.
- The symmetry breaking causes the interaction between different behavioral modes implemented on different time scales.
- The symmetry breaking makes transportation of molecular signals from the front to the rear of the cell during the locomotion.

The cytoplasms of ameboid cells are nonlinearly viscous. The cell controls this viscosity by modulating the amount, localization and interactions of bio-polymers. Here we investigated how the nonlinearity infers the cellular behaviors and whether nonlinearity-specific behaviors exist. We modeled the developed plasmodium of the slime mold Physarum polycephalum as a network of branching tubes and examined the linear and nonlinear viscous cytoplasm flows in the tubes. We found that the nonlinearity in the cytoplasm׳s viscosity induces a novel type of symmetry breaking in the protoplasmic flow. We also show that symmetry breaking can play an important role in adaptive behaviors, namely, connection of behavioral modes implemented on different time scales and transportation of molecular signals from the front to the rear of the cell during cellular locomotion.