Subdiffusive random growth of bacteria

While the regulation of bacterial cell size is widely studied across generations, the stochastic nature of cell volume growth remains elusive within a cell cycle. Here, we investigate the fluctuations of cell volume growth and report a subdiffusive random growth. Specifically, the mean square displacement of the logarithmic volume scales as Δ t α with an anomalous exponent α ≈ 0.27. This low exponent implies strong negative temporal correlations in growth rate noise on timescales of minutes, which are significantly faster than those of gene expression dynamics. We attribute this phenomenon to the physical mechanics of the cell wall. By modeling the cell wall as a complex viscoelastic material with power-law-distributed relaxation times, we successfully recapitulate the observed subdiffusive behavior. Our results suggest that it is the heterogeneous cell-wall viscoelasticity, rather than biological regulatory programs, that governs the short-timescale fluctuations of bacterial growth.