Heat shock response and groEL sequence of Bartonella henselae and Bartonella quintana

Transmission of Bartonella species from ectoparasites to the mammalian host involves adaptation to thermal and other forms of stress. In order to better understand this process, the heat shock response of Bartonella henselae and Bartonella quintana was studied. Cellular proteins synthesized after shift to higher temperatures were intrinsically labelled with [25S]methionine and analysed by gel electrophoresis and fluorography. The apparent molecular masses of three of the major heat shock proteins produced by the two Bartonella species were virtually identical, migrating at 70, 60 and 10 kDa. A fourth major heat shock protein was larger in B. quintana (20 kDa) than in B. henselae (17 kDa). The maximum heat shock response in B. quintana and B. henselae was observed at 39 degrees C and 42 degrees C, respectively. The groEL genes of both Bartonella species were amplified, sequenced and compared to other known groEL genes. The phylogenetic tree based on the groEL alignment places B. quintana and B. henselae in a monophyletic group with Bartonella bacilliformis. The deduced amino acid sequences of Bartonella GroEL homologues contain signature sequences that are uniquely shared by members of the Gram-negative alpha-purple subdivision of bacteria, which live within eukaryotic cells. Recombinant His6-GroEL fusion proteins were expressed in Escherichia coli to generate specific rabbit antisera. The GroEL antisera were used to confirm the identity of the 60 kDa Bartonella heat shock protein. These studies provide a foundation for evaluating the role of the heat shock response in the pathogenesis of Bartonella infection.