Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.21.349696v1?rss=1 Authors: Odermatt, P. D., Bostan, E., Huang, K. C., Chang, F. Abstract: Intracellular density is a critical parameter that impacts the physical nature of the cytoplasm and has the potential to globally affect cellular processes. How density is regulated during cell growth is poorly understood. Here, using a new quantitative phase imaging method, we show that dry-mass density varies during the cell cycle in the fission yeast Schizosaccharomyces pombe. Density decreased during G2 phase, increased in mitosis and cytokinesis, and rapidly dropped at cell birth. These density variations can be explained mostly by a constant rate of biomass synthesis throughout the cell cycle, coupled to slowdown of volume growth during mitosis and cytokinesis and rapid expansion post-cytokinesis. Arrest at specific cell-cycle stages led to continued increases or decreases in density. Spatially heterogeneous patterns of density suggested a link between tip growth and density regulation. Density differences between daughter cells in cells delayed in cytokinesis resulted in bending of the septum away from the high-density daughter, suggesting that intracellular density correlates with turgor pressure. Our results demonstrate that the systematic variations in density during the cell cycle are determined predominantly by modulation of volume expansion, and reveal functional consequences of intracellular density gradients. Copy rights belong to original authors. Visit the link for more info