Faculty Collaboration Database

2-O-methylation of fucosyl residues of a rhizobial lipopolysaccharide is increased in response to host exudate and is eliminated in a symbiotically defective mutant. Appl Environ Microbiol 2004 Mar;70(3):1537-44

Date

03/10/2004

Pubmed ID

15006776

Pubmed Central ID

PMC368319

DOI

10.1128/AEM.70.3.1537-1544.2004

Scopus ID

2-s2.0-1642392484 (requires institutional sign-in at Scopus site)   33 Citations

Abstract

When Rhizobium etli CE3 was grown in the presence of Phaseolus vulgaris seed extracts containing anthocyanins, its lipopolysaccharide (LPS) sugar composition was changed in two ways: greatly decreased content of what is normally the terminal residue of the LPS, di-O-methylfucose, and a doubling of the 2-O-methylation of other fucose residues in the LPS O antigen. R. etli strain CE395 was isolated after Tn5 mutagenesis of strain CE3 by screening for mutant colonies that did not change antigenically in the presence of seed extract. The LPS of this strain completely lacked 2-O-methylfucose, regardless of whether anthocyanins were present during growth. The mutant gave only pseudonodules in association with P. vulgaris. Interpretation of this phenotype was complicated by a second LPS defect exhibited by the mutant: its LPS population had only about 50% of the normal amount of O-antigen-containing LPS (LPS I). The latter defect could be suppressed genetically such that the resulting strain (CE395 alpha 395) synthesized the normal amount of an LPS I that still lacked 2-O-methylfucose residues. Strain CE395 alpha 395 did not elicit pseudonodules but resulted in significantly slower nodule development, fewer nodules, and less nitrogenase activity than lps(+) strains. The relative symbiotic deficiency was more severe when seeds were planted and inoculated with bacteria before they germinated. These results support previous conclusions that the relative amount of LPS I on the bacterial surface is crucial in symbiosis, but LPS structural features, such as 2-O-methylation of fucose, also may facilitate symbiotic interactions.

Author List

Noel KD, Box JM, Bonne VJ

Author

Valerie Bonne MD Assistant Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Carbohydrate Sequence
Fucose
Genes, Bacterial
Lipopolysaccharides
Methylation
Models, Biological
Molecular Sequence Data
Mutation
Phaseolus
Rhizobium etli
Symbiosis