Beijing Genome Institute, Beijing,ChinaINTRODUCTIONBartonella birtlesii (B. birtlesii), like other Bartonellaspecies, has to face various conditions with regardto the presence of haem in its environments(arthropods, mammals, intra- or extracellular).B. birtlesiihas an intraerythrocytic lifestyle in itsnatural host, the mouse. Inside mice, the extra-cellular free haem concentration is low. In con-trast, when invading and multiplying inside theerythrocyte, B. birtlesii has to challenge toxic highhaem concentrations. Similar to other Bartonellaspecies [1], the B. birtlesii genome does not encodefor the haem biosynthesis pathway. The presenceof a haem uptake system is thus important forBartonellae. Here we investigated the function oftwo components of a putative haem uptakesystem encoded in B. birtlesii, and other Bartonellaegenomes.RESULTS AND DISCUSSIONIn silico identification of B. birtlesii genespotentially involved in iron and⁄or haem uptakeAnalysis of the B. birtlesii genome reveals that,similar to other Bartonella species, this a-proteo-bacterium contains only inner membrane ironABC transporters. Genes encoding for an outermembrane iron transporter or a complete sidero-phore biosynthesis pathway are missing in theB. birtlesii genome. Also, the B. birtlesii genomedoes not encode for iron storage proteins (Ftn,Bfn, Dps). In contrast, Bartonellae genomesencode for a complete putative haem transportsystem (Fig. 1). Similar to other bacteria likeNeisseria meningitidis, Bartonellae could use haemas an iron source after its transport and itsdegradation into the cytoplasm. Regulation of theiron-related processes in could simi-larly to other a-proteobacteria involve Mur⁄Fur,RirA and Irr regulators encoded in its genome.Irr was shown to be involved in the regulation ofan outer membrane haem transporter in Brady-rhizobium japonicum. The modulation of the leveland the activity of the components of the haemuptake machinery might be important for theBartonellae lifestyle. Characterisation of Bartonellatribocorum hutA, tonB and exbB mutants as abac-teriaemic strains also underlines the importanceof the haem uptake process in Bartonellae [2].We undertook a functional characterisation ofB. birtlesii HutA [3] and TonB [4], two compo-nents required for the transport of haem throughthe outer membrane. HutA, already characterisedin Vibrio cholerae, transports haem through theouter membrane and requires energy transmittedby the TonB protein [3].Expression and activity of TonB from B. birtlesiiexpressed in Escherichia coliThe tonB structural gene from B. birtlesii wasamplified and cloned in vector pBAD24 givingpBAD24::tonBB.bir. To test activity of TonB fromB. birtlesii, we introduced plasmid pBAD24::ton-BB.bir in strain C600tonB. The strain C600tonBpBAD24::tonBB.bir was tested for growth on LBplates in the presence of the strong Fe