Isolation and characterization ofAzospirillum lipoferumlocus that complementsRhizobium meliloti dctAanddctBmutations

Abstract

A DNA probe containing the structural gene for dicarboxylate transport (dctA) of Rhizobium meliloti hybridized strongly with the fragments of Azospirillum lipoferum genomic DNA. A genomic library of A. lipoferum was screened for the dctA gene by complementation of a dctA mutant of Rhizobium meliloti. A recombinant cosmid, p37D, capable of restoring growth of the dctA mutant on dicarboxylates was isolated and found to hybridize to the dctA probe. The ability of p37D to complement the dctB mutant of R. meloliti indicated that dctA and dctB genes in A. lipoferum may be organized adjacent to each other.Key words: Azospirillum lipoferum, dicarboxylate transport gene, complementation cloning.