Universal protein fluctuations in populations of microorganisms

TL;DR

This study reveals that protein fluctuations across microbial populations follow a universal, non-Gaussian distribution characterized by a quadratic mean-variance relationship, indicating a common underlying regulatory principle.

Contribution

It demonstrates that diverse biological conditions produce a universal protein fluctuation distribution, suggesting a buffering mechanism that masks specific molecular details.

Findings

Protein distributions collapse to a single non-Gaussian curve after scaling.

Variance depends quadratically on the mean across experiments.

Protein fluctuations are governed by a single degree of freedom.

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.