Induction of dnaK through its native heat shock promoter is necessary for intramacrophagic replication of Brucella suis

The heat shock protein DnaK is essential for intramacrophagic replication of Brucella suis. The replacement of the stress-inducible, native dnaK promoter of B. suis by the promoter of the constitutively expressed bla gene resulted in temperature-independent synthesis of DnaK. In contrast to a dnaK null mutant, this strain grew at 37degreesC, with a thermal cutoff at 39degreesC. However, the constitutive dnaK mutant, which showed high sensitivity to H2O2-mediated stress, failed to multiply in murine macrophage-like cells and was rapidly eliminated in a mouse model of infection, adding strong arguments to our hypothesis that stress-mediated and heat shock promoter-dependent induction of dnaK is a crucial event in the intracellular replication of B. suis.