PHYSICAL AND GENETIC-MAP OF THE OBLIGATE INTRACELLULAR BACTERIUM COXIELLA-BURNETII

Pulsed-field gel electrophoresis and PCR techniques have teen used to construct a NotI macrorestriction map of the obligate intracellular ba cterium Coxiella burnetii Nine Mile. The size of the chromosome has be en determined to be 2,103 kb comprising 29 NotI restriction fragments. The average resolution is 72.5 kb, or about 3.5% of the genome. Exper imental data support the presence of a linear chromosome. Published ge nes were localized on the physical map by Southern hybridization, One gene, recognized as transposable element, was found to be present in a t least nine sites evenly distributed over the whole chromosome, There is only one copy of a 16S rRNA gene. The putative oriC has been locat ed on a 27.5-kb NotI fragment, Gene organization upstream the oriC is almost identical to that of Pseudomonas putida and Bacillus subtilis, whereas gene organization downstream the oriC seems to be unique among bacteria. The physical map will be helpful in investigations of the g reat heterogeneity in restriction fragment length polymorphism pattern s of different isolates and the great variation in genome size. The ge netic map will help to determine whether gene order in different isola tes is conserved.