Coordination of contractility, adhesion and flow in migratingPhysarumamoebae

Abstract

This work examines the relationship between spatio-temporal coordination of intracellular flow and traction stress and the speed of amoeboid locomotion of microplasmodia of Physarum polycephalum. We simultaneously perform particle image velocimetry and traction stress microscopy to measure the velocity of cytoplasmic flow and the stresses applied to the substrate by migrating Physarum microamoebae. In parallel, we develop a mathematical model of a motile cell which includes forces from the viscous cytosol, a poro-elastic, contractile cytoskeleton and adhesive interactions with the substrate. Our experiments show that flow and traction stress exhibit back-to-front-directed waves with a distinct phase difference. The model demonstrates that the direction and speed of locomotion are determined by this coordination between contraction, flow and adhesion. Using the model, we identify forms of coordination that generate model predictions consistent with experiments. We demonstrate that this coordination produces near optimal migration speed and is insensitive to heterogeneity in substrate adhesiveness. While it is generally thought that amoeboid motility is robust to changes in extracellular geometry and the nature of extracellular adhesion, our results demonstrate that coordination of adhesive forces is essential to producing robust migration.

Oscillations and uniaxial mechanochemical waves in a model of an active poroelastic medium: Application to deformation patterns in protoplasmic droplets of Physarum polycephalum

“…Very recently, models based on the poroelastic nature of Physarum cell have been proposed to rationalize the mechanism of locomotion of migrating microplasmodia [27,28]. The concept of Physarum cells as being poroelastic media was used previously in a series of studies aiming at understanding the dynamics of the reorganization of protoplasmic droplets and the related deformation patterns [3,44,45].…”

“…The morphology of such networks is analyzed from the point of view of the physiology [14,16,17,18] as well as in the frame of graph theory [19,20,21,22,23]. On the other hand, the scientific focus also lies on small cellular structures of about 50 -800 µm length, where the amoeboid motility of migrating microplasmodia [24,25,26,27,28,29,30] is currently intensively investigated.…”

Mechanochemical pattern formation in simple models of active viscoelastic fluids and solids

“…Other aspects of the spatiotemporal dynamics of Physarum polycephalum such as percolation of small plasmodia into a transport network [12] and the frontal extension dynamics of a bigger cell [13] have been explored experimentally recently. A current focus of (mostly) experimental and theoretical studies is the investigation of migrating plasmodia [14,15,16,17].…”

Two-Layer Elastographic 3-D Traction Force Microscopy

“…We subsequently excised 200- μ m sized pieces with a scalpel and placed them over the polyacrylamide gel. This process produces highly motile amoebae3536. We then removed the surrounding water using a small glass capillary tube, and covered the polyacrylamide gel with the amoebae using an agar cap.…”