Growth rate

Log curve

A sigmoid growth curve is commonly described by four parameters:

1. The natural logarithm of the initial cell concentration (y0).
The initial concentration is a random variable that is specific to each food and not related to the current environment.

2. The time in lag phase (l).
The length of the lag phase will depend on the intrinsic characteristics of the bacteria, the current environmental conditions and the physiological history of the cells.

3. The maximum specific growth rate (µmax).
This represents the steepest slope of the curve. It is considered to be an intrinsic characteristic of the organism dependent on the current environment but not affected by the cell history.

4. The natural logarithm of the maximum cell concentration (ymax).