Genetic analysis of a cluster of genes required for synthesis of the calcofluor-binding exopolysaccharide of Rhizobium meliloti.
Rhizobium meliloti produces an acidic, Calcofluor-binding exopolysaccharide which plays a role in nodulation of alfalfa plants by this bacterium. We constructed and mapped 102 transposon insertions in a 48-kilobase (kb) region previously shown to contain several exo genes. Mutations affecting production of the Calcofluor-binding exopolysaccharide were clustered in a 22-kb region and fell into 12 complementation groups. Strains carrying mutations in seven of the complementation groups (exoA, exoB, exoF, exoL, exoM, exoP, and exoQ) produced no Calcofluor-binding exopolysaccharide and induced non-nitrogen-fixing nodules on alfalfa. Mutants in an eighth complementation group, exoH (Leigh et al., Cell 51:579-587, 1987), produce an altered exopolysaccharide and also induce the formation of non-nitrogen-fixing nodules. Mutants in the remaining four complementation groups produced less Calcofluor-binding material than the wild type. Mutants carrying mutations in two of these complementation groups (exoK and exoN) formed apparently normal, nitrogen-fixing nodules, while mutants in the other two groups (exoG and exoJ) formed normal nodules less efficiently than the wild type.
Long
S
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Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Reed
J W
JW
Himawan
J
J
Walker
G C
GC
D001557:Benzenesulfonates / Q000378:metabolism; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D000455:Medicago sativa; D005810:Multigene Family; D009154:Mutation; D010641:Phenotype; D010957:Plasmids; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D012231:Rhizobium / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D014158:Transcription, Genetic
D001557:Benzenesulfonates; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D011135:Polysaccharides, Bacterial; C007061:C.I. Fluorescent Brightening Agent 28