The particular behaviour of Listeria monocytogenes under sub-optimal conditions

Listeria monocytogenes is a ubiquitous pathogenic microorganism which has been described as growing at temperatures of interest to food production and especially at low temperatures (-2 degrees to 8 degrees C) in storage process. However, the general relationship between the maximum specific growth rate, mumax and temperature has not often been studied for L. monocytogenes in the whole temperature range from minimal to maximal growth temperature. A global analysis of this relationship for temperatures between -2 degrees C and 42 degrees C was therefore done. The global shape of this relationship was that usually observed for microorganisms, especially in the neighbourhood of the optimal temperature, Topt. But a more detailed study showed the existence of a so-called "change temperature", occurring between 10 degrees and 15 degrees C, below which L. monocytogenes grows faster than one would expect. This implies that the minimal growth temperature of both studied strains of L. monocytogenes is lower than expected.