title: Surface polysaccharide mutants of Rhizobium sp. (Acacia) strain GRH2: major requirement of lipopolysaccharide for successful invasion of Acacia nodules and host range determination.
abstract: Two transposon Tn5-induced mutants of wild-type broad-host-range Rhizobium sp. GRH2 were isolated and found to harbour different alterations in surface polysaccharides. These mutants, designated GRH2-14 and GRH2-50, induced a few, empty nodules on Acacia and lost the ability to nodulate most host herbaceous legumes. Whereas mutant GRH2-14 produces an acidic exopolysaccharide (EPS) similar to the wild-type, the acidic EPS of mutant GRH2-50 lacks galactose and the pyruvyl and 3-hydroxybutyryl substituents attached to this sugar moiety. In addition, both mutants GRH2-50 and GRH2-14 were altered in smooth lipopolysaccharides (LPS). DNA sequence analyses of the corresponding Tn5 insertions revealed that strain GRH2-50 was mutated in a DNA locus homologous to galE, and in vitro enzyme assays indicated that the UDPglucose 4-epimerase (GalE) activity was missing in this mutant strain. DNA hybridization studies showed that the GRH2-50 mutant DNA has homologous sequences within the different biovars of Rhizobium leguminosarum. However, no DNA homology to GRH2-14 altered DNA was found in those rhizobial strains, indicating that it represents a new chromosomal lps locus in Rhizobium sp. (Acacia) involved in symbiotic development.
authors.affiliation: Department of Microbiology, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Cientificas, Granada, Spain.
authors.forename: I M
authors.initials: IM
authors.lastname: López-Lara
authors.forename: G
authors.initials: G
authors.lastname: Orgambide
authors.forename: F B
authors.initials: FB
authors.lastname: Dazzo
authors.forename: J
authors.initials: J
authors.lastname: Olivares
authors.forename: N
authors.initials: N
authors.lastname: Toro
mesh_terms: D000045:Acacia / Q000382:microbiology* / Q000648:ultrastructure; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D005816:Genetic Complementation Test; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009154:Mutation; D010641:Phenotype; D015183:Restriction Mapping; D012231:Rhizobium / Q000235:genetics* / Q000502:physiology* / Q000648:ultrastructure; D013559:Symbiosis / Q000235:genetics / Q000502:physiology; D014534:UDPglucose 4-Epimerase / Q000235:genetics / Q000378:metabolism
chemical_list: D017931:DNA Primers; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D008070:Lipopolysaccharides; D014534:UDPglucose 4-Epimerase