We demonstrate here that Tarp orthologs from Chlamydia pneumonia, C. caviae, C. muridarum and various C. trachomatis serovars all harbor at least one and up to four functional actin binding domains and that purified recombinant Tarps from all chlamydial species were capable of nucleating actin filament formation in vitro. Here, TARP is linked to chlamydia trachomatis infectious disease.