ISOLATION AND CHARACTERIZATION OF AZOSPIRILLUM-LIPOFERUM LOCUS THAT COMPLEMENTS RHIZOBIUM-MELILOTI DCTA AND DCTB MUTATIONS

A DNA probe containing the structural gene for dicarboxylate transport (dct A) of Rhizobium meliloti hybridized strongly with the fragments of Azospirillum lipoferum genomic DNA. A genomic library of A. lipofer um was screened for the dct A gene by complementation of a dct A mutan t of Rhizobium meliloti. A recombinant cosmid, p37D, capable of restor ing growth of the dct A mutant on dicarboxylates was isolated and foun d to hybridize to the dct A probe. The ability of p37D to complement t he dct B mutant of R. melolitti indicated that dct A and dct B genes i n A. lipoferum may be organized adjacent to each other.