CHARACTERIZATION OF THE THERMAL-STRESS RESPONSE OF CAMPYLOBACTER-JEJUNI

Campylobacter jejuni, a microaerophilic, gram-negative bacterium, is a common cause of gastrointestinal disease in humans. Heat shock protei ns are a group of highly conserved, coregulated proteins that play imp ortant roles in enabling organisms to cope with physiological stresses . The primary aim of this study was to characterize the heat shock res ponse of C.jejuni. Twenty-four proteins were preferentially synthesize d by C, jejuni immediately following heat shock Upon immunoscreening o f Escherichia coli transformants harboring a Campylobacter genomic DNA library, one recombinant plasmid that encoded a heat shock protein wa s isolated. The recombinant plasmid, designated pMEK20, contained an o pen reading frame of 1,119 bp that was capable of encoding a protein o f 372 amino acids with a calculated molecular mass of 41,435 Da. The d educed amino acid sequence of the open reading frame shared similarity with that of DnaJ, which belongs to the Hsp-40 family of molecular ch aperones, from a number of bacteria. An E, coli dnaJ mutant was succes sfully complemented with the pMEK20 recombinant plasmid, as judged by the ability of bacteriophage lambda to form plaques, indicating that t he C, jejuni gene encoding the 41-kDa protein is a functional homolog of the dnaJ gene from E. coli, The ability of each of two C.jejuni dna J mutants to form colonies at 46 degrees C was severely retarded, indi cating that DnaJ plays an important role in C.jejuni thermotolerance. Experiments revealed that a C,jejuni DnaJ mutant was unable to coloniz e newly hatched Leghorn chickens, suggesting that heat shock proteins play a role in vivo.