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JOURNAL OF BACTERIOLOGY, May 1987, p. 2177-2186 Vol. 169, No. 5 0021-9193/87/052177-10$02.00/0
 

Summary: JOURNAL OF BACTERIOLOGY, May 1987, p. 2177-2186 Vol. 169, No. 5
0021-9193/87/052177-10$02.00/0
Copyright 1987, American Society for Microbiology
Isolation and Characterization of Symbiotic Mutants of
Bradyrhizobium sp. (Arachis) Strain NC92: Mutants with
Host-Specific Defects in Nodulation and Nitrogen Fixationt
KATE J. WILSON,' V. ANJAIAH,2 P. T. C. NAMBIAR,2 AND FREDERICK M. AUSUBEL1*
Department of Genetics, Harvard Medical School, and Department ofMolecular Biology, Massachusetts General
Hospital, Boston, Massachusetts 02114,1 and International Crops Research Institute for the Semi-Arid Tropics,
Andhra Pradesh 502 324, India2
Received 4 November 1986/Accepted 6 February 1987
Random transposon TnS mutagenesis ofBradyrhizobium sp. (Arachis) strain NC92, a member of the cowpea
cross-inoculation group, was carried out, and kanamycin-resistant transconjugants were tested for their
symbiotic phenotype on three host plants: groundnut, siratro, and pigeonpea. Two nodulation (Nod-
phenotype) mutants were isolated. One is unable to nodulate all three hosts and appears to contain an insertion
in one of the common nodulation genes (nodABCD); the other is a host-specific nodulation mutant that fails to
nodulate pigeonpea, elicits uninvaded nodules on siratro, and elicits normal, nitrogen-fixing nodules on
groundnut. In addition, nine mutants defective in nitrogen fixation (Fix- phenotype) were isolated. Three fail
to supply symbiotically fixed nitrogen to all three host plants. Surprisingly, nodules elicited by one of these
mutants exhibit high levels of acetylene reduction activity, demonstrating the presence of the enzyme

  

Source: Ausubel, Frederick M. - Department of Genetics, Harvard University

 

Collections: Biology and Medicine