PHYSICAL MAP OF THE CHROMOSOME OF THE PHYTOPATHOGENIC BACTERIUM PSEUDOMONAS-SYRINGAE PV. PHASEOLICOLA

Pseudomonas syringae pv. phaseolicola (P.s. phaseolicola) is one of ab out 45 recognized pathovars within the P. syringae group and is the ca usal agent of halo-blight disease of beans. DNA from this bacterium di gested to completion with two different restriction enzymes, PacI and PmeI, yielded 15 and 16 fragments, respectively. These were separated using PFGE and sized by comparison to known molecular mass markers. Th e P.s. phaseolicola chromosome was determined to be approximately 5.64 Mb in size. To link the different fragments obtained into a circular chromosome map for both enzymes, 150 random Tn5 mutants of P.s. phaseo licola were used as a source of DNA and the identification of the band carrying the transposon 'tag' in each mutant was done after PFGE and Southern hybridization of a complete chromosomal digestion using a Tn5 probe. Partial digestions of DNA from different Tn5 mutants 'tagging' specific bands were then generated and the complete and partial produ cts of the digestion separated by PFGE and identified with a Tn5 probe . By calculating the size of the partial products, it was then possibl e to link different bands into a physical map. This is the first repor t on the construction of a physical map of a member of the P. syringae group and should be invaluable for molecular genetic analysis in this species and in evolutionary or taxonomic studies when compared to sim ilar data obtained for any of the other recognized pathovars.