Aims: Non‐sigmoid growth curves of Escherichia coli obtained at constant temperatures near the maximum growth temperature (Tmax) were previously explained by the coexistence of two subpopulations, i.e. a stress‐sensitive and a stress‐resistant subpopulation. Mathematical simulations with a heterogeneous model support this hypothesis for static experiments at 45°C. In this article, the behaviour of E. coli, when subjected to a linearly increasing temperature crossing Tmax, is studied.
Methods and Results: Subpopulation dynamics are studied by culturing E. coli K12 MG1655 in brain heart infusion broth in a bioreactor. The slowly increasing temperature (°C h−1) starting from 42°C results in growth up to 60°C, a temperature significantly higher than the known Tmax. Given some additional presumptions, mathematical simulations with the heterogeneous model can describe the dynamic experiments rather well.
Conclusions: This study further confirms the existence of a stress‐resistant subpopulation and reveals the unexpected growth of E. coli at temperatures significantly higher than Tmax.
Significance and Impact of the Study: The growth of the small stress‐resistant subpopulation at unexpectedly high temperatures asks for a revision of currently applied models in food safety and food quality strategies.