Southern analysis of LES phage integration sites in LESB58 and PAO1. Southern blot analysis to determine LES phage copies and integration sites in LESB58 and PLPL chromosomes: A) PstI digested LES phage lysogens hybridised to LESφ2 integrase (int) probe; B) DraIII digested LES phage lysogens hybridised to LESφ3 integrase probe; C) AcuI digested LES phage lysogens hybridised to LESφ4 cI probe. A diagrammatical representation of the restriction pattern is presented below each blot. This demonstrates the expected size of fragments that would hybridise each probe in the event of single phage integration (one band) or integration of two identical prophages in tandem (two bands). For clarity, the second phage copy has been shaded in grey. The 2-band pattern would also result if any additional phage copies were present in circular form.