Cell-to-cell variation and specialization in sugar metabolism in clonal bacterial populations
Fig 1
Isotopic composition of the biomass and heterogeneity in sugar assimilation.
A Carbon and hydrogen from different sources were assimilated into the biomass of cells growing in carbon-limited chemostats. The chemostats were operated at a dilution rate of 0.15 h-1 corresponding to 25% of the maximum growth rate μMAX (see S2 File for μMAX). Carbon was mostly 12C, except carbon originating from arabinose (depicted in blue) that was 99% 13C-labeled. Assimilable organic carbon (AOC, green) presented a considerable fraction of the total assimilated carbon. Hydrogen was mostly 1H, except hydrogen originating from glucose (red) that was 97% 2H-labeled. Hydrogen from water and AOC (green) presented a considerable fraction of the total assimilated hydrogen. Carbon and hydrogen assimilated before switching to media with labeled sugars remained the main contributors to the biomass (depicted in purple) (for calculations see S2 File, ‘Mathematical Model’). B Individual cells showed variation in the assimilation of glucose and arabinose. Each data point indicates excess atom fractions of a single cell in carbon-limited and nitrogen-limited (carbon-excess) chemostats, determined for 2H assimilation from labeled glucose as XE (2H)cell, and for 13C assimilation from labeled arabinose as XE (13C)cell. Population size in both chemostat setups was similar, about 2.4 x 106 cells/ml. Populations growing in mixed-substrate carbon-limited chemostats assimilated both sugars, whereas populations growing in nitrogen-limited chemostats utilized solely glucose under a regime of catabolite repression. Replicate cultures are plotted in different colors.