Differential heat-shock protein synthesis and response to stress in three avirulent and virulent Listeria species.

Two strains of Listeria monocytogenes, a virulent (V) and an avirulent (A) strain obtained by repeated in vitro cultivation at 37 degrees C, exhibited differing constitutive syntheses of heat-shock proteins (HSP) at 37 degrees C, the temperature of the infected host, and a differential response to heat treatment. These two strains also reacted differently to addition of a superoxide ion inducer and acid to treatments. Our observations were not limited to these two strains of L. monocytogenes: the level of HSP synthesis at 37 degrees C varied from one species of Listeria to another and was correlated with the thermo-inducibility of HSP. In an accompanying paper, we will attempt to establish whether these different biosynthetic properties observed in vitro between A and V L. monocytogenes enable the prediction of their properties/survival once inside the resident peritoneal murine macrophages.