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JOURNAL OF BACTERIOLOGY, Jan. 1982, p. 114-122 0021-9193/82/010114-09$02.00/0
 

Summary: JOURNAL OF BACTERIOLOGY, Jan. 1982, p. 114-122
0021-9193/82/010114-09$02.00/0
Vol. 149, No. 1
Physical and Genetic Characterization of Symbiotic and
Auxotrophic Mutants of Rhizobium meliloti Induced by
Transposon TnS Mutagenesis
HARRY M. MEADE, SHARON R. LONG, GARY B. RUVKUN, SUSAN E. BROWN, AND FREDERICK
M. AUSUBEL*
Cellular and Developmental Group, Department ofBiology, Biological Laboratories, Harvard University,
Cambridge, Massachusetts 02138
Received 26 May 1981/Accepted 26 August 1981
We have physically and genetically characterized 20 symbiotic and 20 auxotro-
phic mutants of Rhizobium meliloti, the nitrogen-fixing symbiont of alfalfa
(Medicago sativa), isolated by transposon TnS mutagenesis. A "suicide plasmid"
mutagenesis procedure was used to generate TnS-induced mutants, and both
auxotrophic and symbiotic mutants were found at a frequency of 0.3% among
strains containing random TnS insertions. Two classes of symbiotic mutants were
isolated: 4 ofthe 20 formed no nodules at all (Nod-), and 16 formed nodules which
failed to fix nitrogen (Fix-). We used a combination of physical and genetic
criteria to determine that in most cases the auxotrophic and symbiotic phenotypes

  

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

 

Collections: Biology and Medicine