Transformation of Rickettsia prowazekii to erythromycin resistance encodedby the Escherichia coli ereB gene

Rickettsia prowazekii, the etiologic agent of epidemic typhus, is an obliga te, intracytoplasmic, parasitic bacterium. Recently, the transformation of this bacterium via electroporation has been reported. However, in these stu dies identification of transformants was dependent upon either selection of an R. prowazekii rpoB chromosomal mutation imparting rifampin resistance o r expression of the green fluorescent protein and how cytometric analysis. In this paper we describe the expression in R. prowazekii of the Escherichi a coli ereB gene. This gene codes for an erythromycin esterase that cleaves erythromycin. To the best of our knowledge, this is the first report of th e expression of a nonrickettsial, antibiotic-selectable gene in R. prowazek ii. The availability of a positive selection for rickettsial transformants is an important step in the characterization of genetic analysis systems in the rickettsiae.