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Updated: May 18, 2026

Measuring Microbial Mutation Rates with the Fluctuation Assay
Published on: November 28, 2019
Universal protein fluctuations in populations of microorganisms
Hanna Salman1, Naama Brenner, Chih-kuan Tung
1Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
Abstract:
The copy number of any protein fluctuates among cells in a population; characterizing and understanding these fluctuations is a fundamental problem in biophysics. We show here that protein distributions measured under a broad range of biological realizations collapse to a single non-gaussian curve under scaling by the first two moments. Moreover, in all experiments the variance is found to depend quadratically on the mean, showing that a single degree of freedom determines the entire distribution. Our results imply that protein fluctuations do not reflect any specific molecular or cellular mechanism, and suggest that some buffering process masks these details and induces universality.
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