Artificial cells in picoliter droplets
Wilhelm T. S. Huck
Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands
A cell is the common unit structure shared by all living organisms, but even ‘simple’ prokaryotic cells are extremely complex chemical reactors. Despite enormous progress in our understanding of the complex relationships between all the individual components in the cell, we do not understand the basic underlying physical chemistry of the cell. In this talk I will show initial results of our studies into new protocells formed by coacervation. Compartmentalization via lipid bilayers is considered essential for the emergence of cells,1 but there are alternative routes to membrane-free compartments arising from liquid-liquid phase transitions.2,3 However, it is unknown if and how coacervation of collections of proteins and other molecules can form compartments capable of executing complex sets of reactions. To study this, we developed a method based on picoliter water-in-oil droplets4 that allows us to induce coacervation in Escherichia coli cell lysate and follow in vitro transcription and translation under crowded and non-crowded conditions. Coacervation creates an artificial cell-like environment in which the rate of mRNA production is increased significantly. The effect of crowding on the kinetics of the fundamental machinery of gene expression has a direct impact on our understanding of biochemical networks in vivo. Moreover, our results show the intrinsic potential of cellular components to drive phase separation and to facilitate macromolecular organization into membrane-free compartments.5,6
1 Szostak, J. W., Bartel, D. P. & Luisi, P. L. Synthesizing life. Nature 409, 387-390 (2001).
2 Oparin, A. I. The Origin of Life. (Dover Publications, Inc, 1953).
3 Hyman, A. A. & Simons, K. Beyond Oil and Water-Phase Transitions in Cells. Science 337, 1047-1049 (2012).
4 Theberge, A. B. et al. Microdroplets in Microfluidics: An Evolving Platform for Discoveries in Chemistry and Biology. Angew Chem Int Edit 49, 5846-5868 (2010).
5 Sokolva et al. Enhanced transcription rates in membrane-free protocells formed by coacervation of cell lysate Proc. Nat. Acad. Sci. USA 110, 11692-11697 (2013).
6 Hansen et al. Macromolecular crowding creates heterogeneous environments of gene expression in picolitre droplets Nature Nanotechnology 11, 191-197 (2016).