Measurement of mass, density, and volume during the cell cycle of yeast

Abstract

Cell growth comprises changes in both mass and volume-two processes that are distinct, yet coordinated through the cell cycle. Understanding this relationship requires a means for measuring each of the cell's three basic physical parameters: mass, volume, and the ratio of the two, density. The suspended microchannel resonator weighs single cells with a precision in mass of 0.1% for yeast. Here we use the suspended microchannel resonator with a Coulter counter to measure the mass, volume, and density of budding yeast cells through the cell cycle. We observe that cell density increases prior to bud formation at the G1/S transition, which is consistent with previous measurements using density gradient centrifugation. To investigate the origin of this density increase, we monitor relative density changes of growing yeast cells. We find that the density increase requires energy, function of the protein synthesis regulator target of rapamycin, passage through START (commitment to cell division), and an intact actin cytoskeleton. Although we focus on basic cell cycle questions in yeast, our techniques are suitable for most nonadherent cells and subcellular particles to characterize cell growth in a variety of applications.biosensor | cell growth | cell size | microfluidics | Saccharomyces

The critical size is set at a single-cell level by growth rate to attain homeostasis and adaptation

“…cycle 37,42,50,51 , a discontinuous pattern of growth in volume should cause changes in cell density over the cell cycle, consistent with the fact that yeast cells reach a maximum density shortly after budding 52,53 . All these observations point to a discontinuous mode of volume growth during the cell cycle of budding yeast, a property that has been well established in the fission yeast Schizosaccharomyces pombe 44,45,54 and may also apply to mammalian cells 55 .…”

Measuring single-cell density

“…The cantilever oscillates at a frequency that is proportional to its mass, and a cell passing through the embedded channel changes the resonance frequency of the cantilever by an amount proportional to the buoyant mass of the cell. Previous work with the SMR showed that the average density of a population of cells can be calculated from buoyant mass measurements (10,11) and that yeast exhibit cell cycle-dependent variations in average cell density (11), but these methods cannot measure the density of single cells or derive statistics about the density distribution.…”

Label-free viscosity measurement of complex fluids using reversal flow switching manipulation in a microfluidic channel

“…39,40 Microfluidic platforms have also been adopted to measure fluid viscosity instead of conventional bulky platforms. 32,33 These fluid viscosity measurement methods can be classified into two groups, depending on flow conditions. Under quasi-static flow conditions, fluid viscosity in a microfluidic channel can be determined using laser-induced capillary waves, 41 acoustic-propagated waves, 42 and resonance frequency with a micro-cantilever.…”

“…28 Recently, microfluidic devices with distinctive advantages, including small sample volume, high sensitivity, and point of care feasibility, have been introduced to effectively manipulate small amounts of fluids in microfluidic channels for biomedical applications. For example, several microfluidic platforms have been applied to measure fluid properties such as surface tension, 29,30 density, [31][32][33] pressure drop, [34][35][36] flow rate, 37,38 and fluid resistance. 39,40 Microfluidic platforms have also been adopted to measure fluid viscosity instead of conventional bulky platforms.…”