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. lipoferum was screened for the dct A gene by complementation of a dct A mutant of Rhizobium meliloti. A recombinant cosmid, p37D, capable of restoring growth of the dct A mutant on dicarboxylates was isolated and found to hybridize to the dctA probe. The ability of p37D to complement the dct B mutant of R. meloliti indicated that dct A and dct B genes in A. lipoferum may be organized adjacent to each other.