Characterization of Brucella suis clpB and clpAB mutants and participationof the genes in stress responses

Pathogens often encounter stressful conditions inside their hosts. In the a ttempt to characterize the stress response in Brucella suis, a gene highly homologous to Escherichia coli clpB was isolated from Brucella suis, and th e deduced amino acid sequence showed features typical of the ClpB ATPase fa mily of stress response proteins. Under high-temperature stress conditions, ClpB of B. suis was induced, and an isogenic B. suis clpB mutant showed in creased sensitivity to high temperature, but also to ethanol stress and aci d pH. The effects were reversible by complementation. Simultaneous inactiva tion of clpA and clpB resulted in a mutant that was sensitive to oxidative stress. In B. suis expressing gfp, ClpA but not ClpB participated in degrad ation of the green fluorescent protein at 42 degreesC. We concluded that Cl pB was responsible for tolerance to several stresses and that the lethality caused by harsh environmental conditions may have similar molecular origin s.