Abstract

A microfluidic device containing a suspended microchannel resonator capable of measuring the mass of microscopic objects with femtogram resolution allows determination of bacteria, yeast and mammalian cell growth rates in less than one cell cycle by repeated measurement of the buoyant mass of single growing cells. We used a suspended microchannel resonator (SMR) combined with picoliter-scale microfluidic control to measure buoyant mass and determine the 'instantaneous' growth rates of individual cells. The SMR measures mass with femtogram precision, allowing rapid determination of the growth rate in a fraction of a complete cell cycle. We found that for individual cells of Bacillus subtilis, Escherichia coli, Saccharomyces cerevisiae and mouse lymphoblasts, heavier cells grew faster than lighter cells.