Bacterial cell shape control by nutrient-dependent synthesis of cell division inhibitors

Abstract

By analysing cell shape and size of the bacterium Bacillus subtilis under nutrient perturbations, protein depletion, and antibiotic treatments we find that cell geometry is extremely robust, reflected in a well-conserved scaling relation between surface area (S) and volume (V), S ~ V{gamma}, with{gamma} = 0.85. We develop a molecular model supported by single-cell simulations to predict that the surface-to-volume scaling exponent{gamma} is regulated by nutrient-dependent production of metabolic enzymes that act as cell division inhibitors in bacteria. Using theory that is supported by experimental data, we predict the modes of cell shape transformations in different bacterial species and propose a mechanism of cell shape adaptation to different nutrient perturbations. For organisms with high surface-to-volume scaling exponent{gamma} , such as B. subtilis, cell width is not sensitive to growth rate changes, whereas organisms with low{gamma} , such as A. baumannii, cell shape adapts readily to growth rate changes. SIGNIFICANCEHow bacteria regulate their size and shapes to optimise their growth fitness in different nutrient environments remains largely unknown. By analysing the surface area and volume of rod-shaped B. subtilis exposed to different nutrient conditions and antibiotics we find that cells preserve a power law scaling between surface area and volume. We show that the surface-to-volume scaling is extremely robust and is regulated by nutrient-dependent synthesis of cell division inhibitors. By analysing different bacterial types, we find that cells conserve the surface-to-volume scaling exponent that is typical for each species, implying distinct mechanisms for morphological adaptation in each organism.