Systematic perturbation of cytoskeletal function reveals a linear scaling relationship between cell geometry and fitness

Cell Rep. 2014 Nov 20;9(4):1528-37. doi: 10.1016/j.celrep.2014.10.040. Epub 2014 Nov 13.

Abstract

Diversification of cell size is hypothesized to have occurred through a process of evolutionary optimization, but direct demonstrations of causal relationships between cell geometry and fitness are lacking. Here, we identify a mutation from a laboratory-evolved bacterium that dramatically increases cell size through cytoskeletal perturbation and confers a large fitness advantage. We engineer a library of cytoskeletal mutants of different sizes and show that fitness scales linearly with respect to cell size over a wide physiological range. Quantification of the growth rates of single cells during the exit from stationary phase reveals that transitions between "feast-or-famine" growth regimes are a key determinant of cell-size-dependent fitness effects. We also uncover environments that suppress the fitness advantage of larger cells, indicating that cell-size-dependent fitness effects are subject to both biophysical and metabolic constraints. Together, our results highlight laboratory-based evolution as a powerful framework for studying the quantitative relationships between morphology and fitness.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alleles
  • Clone Cells
  • Cytoskeleton / metabolism*
  • Directed Molecular Evolution
  • Environment
  • Escherichia coli / cytology*
  • Escherichia coli / genetics*
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / metabolism
  • Genetic Fitness*
  • Mutation

Substances

  • Escherichia coli Proteins
  • MreB protein, E coli