Exopolysaccharide-deficient mutants of Rhizobium meliloti that form ineffective nodules
By screening with the fluorescent stain Calcofluor, we have isolated 26 independent transposon Tn5 insertion mutants of Rhizobium meliloti that are deficient in the production of a known extracellular polysaccharide (Exo-). The mutants belonged to six distinct genetic groups based on the ability of...
Saved in:
Published in | Proceedings of the National Academy of Sciences - PNAS Vol. 82; no. 18; pp. 6231 - 6235 |
---|---|
Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Washington, DC
National Academy of Sciences of the United States of America
01.09.1985
National Acad Sciences |
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | By screening with the fluorescent stain Calcofluor, we have isolated 26 independent transposon Tn5 insertion mutants of Rhizobium meliloti that are deficient in the production of a known extracellular polysaccharide (Exo-). The mutants belonged to six distinct genetic groups based on the ability of their Exo-phenotype to be complemented by different recombinant plasmids from a R. meliloti clone bank. With few exceptions, all of the mutants formed ineffective (non-nitrogen-fixing) nodules on alfalfa. For all but one group, the complementing plasmids restored effective nodulation. These results establish a firm and extensive correlation between the ability of Rhizobium to produce a particular polysaccharide and symbiotic proficiency. The ineffective nodules appeared to contain no bacteroids and to form without shepherds' crooks or infection threads; this symbiotic phenotype matches that described for a set of independently isolated mutants that belong phenotypically and genetically to the group B exopolysaccharide mutants described previously [Finan et al. (1985) Cell 40, 869-877]. Apparently the exopolysaccharide, although not required for nodule formation, is involved in wild-type nodule invasion. |
---|---|
Bibliography: | P34 8636042 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0027-8424 1091-6490 |
DOI: | 10.1073/pnas.82.18.6231 |