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Microorganisms maintain crowding homeostasis


Macromolecular crowding affects the mobility of biomolecules, protein folding and stability, and the association of macromolecules with each other. Local differences in crowding that arise as a result of subcellular components and supramolecular assemblies contribute to the structural organization of the cytoplasm. In this Opinion article we discuss how macromolecular crowding affects the physicochemistry of the cytoplasm and how this, in turn, affects microbial physiology. We propose that cells maintain the overall concentration of macromolecules within a narrow range and discuss possible mechanisms for achieving crowding homeostasis. In addition, we propose that the term 'homeocrowding' is used to describe the process by which cells maintain relatively constant levels of macromolecules.

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Figure 1: General principles of macromolecular crowding.
Figure 2: Schematic showing the effect of osmotic stress on the volume of a bacterial cell.
Figure 3: Possible mechanisms of crowding homeostasis.


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Work in the laboratories of the authors was funded by the European FP7 Initial Training Network program Network for Integrated Cellular Homeostasis in Escherichia coli (NICHE; to J.v.d.B.), a The Netherlands Organisation for Scientific Research (NWO) Innovational Research Incentives Scheme (VIDI) grant (to A.J.B.), and a NWO TOPGO (L.10.060) and a European Research Council (ERC) Advanced Grant (ABCVolume) to B.P. The authors thank M. Heinemann, J.-W. Veening and J. Spitzer for the critical reading of this manuscript. The authors also thank M. Guskova for help with the artwork.

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Diffusion coefficient of cytoplasmic GFP (DGFP) in E. coli (orange) and L. lactis (green) as a function of cell volume. Volume reduction was achieved by osmotic upshift. (PDF 111 kb)

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van den Berg, J., Boersma, A. & Poolman, B. Microorganisms maintain crowding homeostasis. Nat Rev Microbiol 15, 309–318 (2017).

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