The orf4 orf5 orf6 gene cluster of pHW4594 is not derived from its host. DNA from different Rahnella strains was digested with Hin dIII (right panel) and subsequently analysed with an orf5 orf6 specific probe (left panel). Two different amounts of DNA were loaded of DSM 4594T, the host strain of pHW4596, to account for plasmid copy number (approximately 3 μg and 0.2 μg in the first and second lane, respectively). The detected band corresponded to the restriction fragment of the plasmid pHW4594 with an expected size of 1.3 kb. The same result was obtained with Hpa II digested DNA (data not shown). GS, genomospecies.