Analysis of the Rhizobium meliloti surface
This project, originally oriented toward the role of the bacterial surface in nodulation and nitrogen fixation, has focused on rhizobial lipopolysaccharide (LPS). LPS mutants from R. meliloti strain SU47 were isolated by selecting bacteria resistant to bacteriophage or deoxycholate solubilization. The four best characterized, of the 13 groups obtained, all map to the bacterial chromosome. All mutants elicit Fix{sup +} nodules on alfalfa, giving little evidence for a role of LPS in symbiosis in R. meliloti, as opposed to other Rhicobium sp. exo mutants (reduced or eliminated extracellular polysaccharide (EPS)) elicit Fix{sup {minus}} nodules on alfalfa, indicating EPS has a role in symbiosis. However, strain SU47 lacks the gene 1psZ, which can repress the Fix{sup {minus}} phenotype caused by exo mutants. 1psZ{sup +} does not restore EPS, but instead alters LPS. This suggests that in R. meliloti, either EPS or a specific LPS conformation is required to generate Fix{sup +} nodules in alfalfa. Mutation at 1psX, 1psY, 1psI or 1psN prevent 1psZ{sup +} suppression of exo, presumably because all five genes (1psI, N, X, Y, Z) are required to obtain the proper form of LPS that can substitute for EPS. In support of the hypothesis, LPS from 1psX, 1psY, or 1psZ have characteristic structures, none of which match wild type LPS. 1psZ{sup +} has been cloud and sequenced. The 1psZ{sup +} protein has a predicted molecular weight of 48,589 and is probably cytoplasmic. 1psZ is constitutively expressed, and 1psZ{sup +} does not suppress exoC, suggesting the exoC product, phosphoglucomutase, may play a role in LPS processing. During this work, a host restriction difference between strains SU47 and Rm 41, inactivable by incubation 42{degree}, was identified. (MHB)
- Research Organization:
- Massachusetts Inst. of Tech., Cambridge, MA (USA)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- FG02-84ER13252
- OSTI ID:
- 5988203
- Report Number(s):
- DOE/ER/13252-5; ON: DE91008977
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
60 APPLIED LIFE SCIENCES
LIPOPOLYSACCHARIDES
BIOLOGICAL FUNCTIONS
POLYSACCHARIDES
RHIZOBIUM
GENE MUTATIONS
ALFALFA
BACTERIOPHAGES
BIOSYNTHESIS
DNA SEQUENCING
DNA-CLONING
EXTRACELLULAR SPACE
GENETIC MAPPING
INHIBITION
MUTANTS
NITROGEN FIXATION
PHENOTYPE
PROGRESS REPORT
PROTEIN STRUCTURE
BACTERIA
CARBOHYDRATES
CLONING
DNA HYBRIDIZATION
DOCUMENT TYPES
FUNCTIONS
HYBRIDIZATION
LEGUMINOSAE
LIPIDS
MAGNOLIOPHYTA
MAGNOLIOPSIDA
MAPPING
MICROORGANISMS
MUTATIONS
ORGANIC COMPOUNDS
PARASITES
PLANTS
SACCHARIDES
SPACE
STRUCTURAL CHEMICAL ANALYSIS
SYNTHESIS
VIRUSES
550400* - Genetics
550200 - Biochemistry
553000 - Agriculture & Food Technology