Compartmental Volume Regulation of E. Coli under Various Growth Conditions

Abstract

The dimensions of bacteria like Escherichia coli are affected by nutrient availability and follow the growth law. We show that metabolic shifts not only affect the volume of the whole cell, but also the relative volumes of cytoplasm and periplasm. Changes in volume affect crowding and turgor pressure, as well as membrane tension and ionic strength. These parameters are known to influence folding of proteins, affinities of biomolecules and interaction rates in vivo.We quantified the volumes of the cytoplasm and the periplasm under different growth conditions, using photoactivated localization microscopy (PALM). In slow growing cells the relative periplasmic volume increases up to three-fold when compared to fast growing cells. In parallel, the expression of periplasmic substrate binding proteins of many ABC transporters was increased, suggesting that slow growing cells increase their capacity to scavenge nutrients for which a larger periplasm is needed. We also find that the periplasm of slow growing cells is more crowded and that the mobility of proteins is lower. Our work indicates that cytoplasm and periplasm show a high plasticity in terms of volume and crowdedness and cells adapt in response to nutrient availability.