# Extending the Square Root Growth Rate Model to Lethal Low Temperatures

Extending the Square Root Growth Rate Model to Lethal Low Temperatures

When the temperature of a microbial population is lowered beyond a certain level, its growth ceases and can become inactive. The phenomenon is reversed upon heating. The temperature effect on the growth rate above the minimal temperature needed for growth has been frequently described by Ratkowski's square root model, a simple, useful variant of the Bĕlehrádek model. This Demonstration provides graphical visualization of an extended version of these models in the region where growth ceases and turns into inactivation or vice versa. The extended model has been constructed by mirroring the temperature effect in the two regimes and allowing for an intermediate temperature range where the population size remains practically unchanged.