PHYSICAL AND GENETIC-MAP OF A MAJOR NIF GENE-CLUSTER FROM FRANKIA STRAIN FAC1

Cosmid clone pFAH1, a genomic clone of Frankia FaC1, was mapped using restriction enzymes and the position of nif genes in the clone was det ermined by a combination of hybridization and nucleotide sequence anal ysis. pFAH1 was estimated to be about 44 kb by summation of the indivi dual fragment length generated by single or double restriction endonuc lease digestion. To assist in constructing the restriction map of the pFAH1, EcoRI-14 kb, EcoRI/HindIII-8.5 kb, and EcoRI/HindIII-4.5 kb wer e subcloned into the cosmid vector, pHC79 and named pFE14, pFEH8.5, an d pFEH4.5, respectively. EcoRI-17 kb was also self ligated and named p FE17. Southern hybridization analyses with Azotobacter vinelandii nif genes as probes and partial sequencing analyses of the subclones revea led that the organization of the nif genes in the FaC1 strain was nifV , H, D, K, E, N, X, W, B.