Modelling Population Dynamics of Pseudomonas Putida KT2440 Under Various Growth Conditions

A bacterial population which is exposed to stressful industrial production environments may convert into subpopulations with reduced or stopped product formation properties. Consequently, overall process performance deteriorates, because tools to prevent these developments are still unknown. Using P. putida KT2440 as a model system, we quantified population heterogeneities under standard conditions and in stress response to oxygen limitation and solvent stress in controlled continuous cultivations.

Stressed cells showed an early wash-out in comparison to non-stressed cells. Single cell analysis revealed a split-up of the clonal population into two subpopulations. The ratio of subpopulations with single DNA and double DNA content were investigated at steady-state in stressed and non-stressed set-ups. Stressed populations showed a higher pronounced continuous shift of this ratio towards cells containing a double DNA content.

DNA distribution reflects information of growth rate on subpopulation level and mirrors changes in environmental surroundings. The observed shifts in subpopulation ratios indicate influences on the level of cell cycling. Steady state analysis of DNA contents is integrated into a mechanistic model of cell cycling. Cell cycle parameters were estimated by comparison of simulated to experimentally derived DNA content histograms. The comparison of the relevant parameters in stressed versus non stressed growth conditions gives valuable insights into quantitative understanding of subpopulation split-up and highlights the influence of typical production stress conditions on population dynamics.

This project is funded within the ERA-IB / ERA-NET Scheme of the 6th EU Framework Programme (0315932B)