Genome-Based Constructionof the Metabolic Pathways ofOrientia tsutsugamushiand Comparative Analysis within theRickettsiales Order

摘要

Orientia tsutsugamushi, the causative agent of scrub typhus, is an obligate intracellular bacterium that belongs to the order of Rickettsiales. Recently, we have reported that O. tsutsugamushi has a unique genomic structure, consisting of highly repetitive sequences, and suggested that it may provide valuable insight into the evolution of intracellular bacteria. Here, we have used genomic information to construct the major metabolic pathways of O. tsutsugamushi and performed a comparative analysis of the metabolic genes and pathways of O. tsutsugamushi with other members of the Rickettsiales order. While O. tsutsugamushi has thelargest genome among the members of this order,mainly due to the presence of repeatedsequences, its metabolic pathways have beenhighly streamlined. Overall, the metabolicpathways of O. tsutsugamushiwere similar to Rickettsia butthere were notable differences in severalpathways including carbohydrate metabolism, theTCA cycle, and the synthesis of cell wallcomponents as well as in the transport systems.Our results will provide a useful guide to thepostgenomic analysis ofO. tsutsugamushi and leadto a better understanding of the virulence andphysiology of this intracellular pathogen.