In a recent collaborative effort (with Simon Alberti, MPI-CBG, and Jochen Guck, MPL Erlangen) we have discovered that single-cell organisms such as yeast or amoeba can survive energy depletion by transforming their cytoplasm from a fluid-like state to a solid-like state. We used several techniques such as passive microrheology, AFM measurements, and real-time deformability cytometry to demonstrate that cells transition to a state with pronounced elastic properties. Figure shows the trajectories of tracer particles in budding yeast cells in two different states: high exploration of cytoplasm in the fluid-like state (left) and almost no motion in the solid-like state (right). It was shown that the major cause of this transition is the drop in intracellular pH which leads to a widespread self-assembly of cytosolic proteins.
We have planned an extensive program to further develop this line of research. We aim to understand the nature of the solid-like state in the energy depleted cells. In collaboration with the group of Teymuras Kurzchalia, MPI-CBG, we will focus on the related transition of the cells and organisms (C.elegans worm) during desiccation. It was previously shown in plant seeds, that the increased accumulation of certain sugars (sucrose in plants and trehalose in C.elegans) leads to the glass transition in seeds at the removal of water. What is the physical mechanism of sugars conservative role remains poorly understood and we would like to contribute to answering this challenging question.
Intracellular mass density increase is accompanying but not sufficient for stiffening and growth arrest of yeast cells;
S. Abuhattum, K. Kim, T. Franzmann, A. Eßlinger, D. Midtvedt, R. Schlüßler, S. Möllmert, H.S. Kuan, S. Alberti, V. Zaburdaev and J. Guck, Frontiers in Physics, 6:131 (2018)
A pH-driven transition of the cytoplasm from a fluid- to a solid-like state promotes entry into dormancy; M.C. Munder, D.Midtvedt, T. Franzmann, E. Nüske, O. Otto, M. Herbig, E.Ulbricht, P. Müller, A. Taubenberger, S. Maharana, L. Malinovska, D. Richter, J. Guck, V. Zaburdaev, and S. Alberti, eLife 2016;5:e09347 (2016)