Rickettsia prowazekii and Bartonella henselae: Differences in the intracellular life styles revisited

Within the alpha subdivision of proteobacteria, the arthropod-borne human p athogens Rickettsia prowazekii and Bartonella henselae provide examples of bacteria with obligate and facultative intracellular life styles, respectiv ely. The complete genome sequence of R. prowazekii has been published, wher eas the sequencing of the B, henselae genome is in its final stage. Here, w e provide a brief overview of a comparative analysis of both genomes based on the delineated metabolic properties. The relative proportion of genes de voted to basic information processes is similar in the two genomes. In cont rast, a full set of genes encoding proteins involved in the biosynthesis of amino acids and nucleotides is present in B. henselae, while the majority of these genes is absent from R. prowazekii. This suggests that B. henselae has a better potential for growth in the free-living mode, whereas R. prow azekii is more specialised to growth in an intracellular environment. Funct ional genomics will provide the potential to further resolve the genetic ba sis for successful human infections by these important parasites.