RESUMEN
Rhizobitoxine is a phytotoxin synthesized by some strains of the legume symbiont genus Bradyrhizobium and the plant pathogen Pseudomonas andropogonis. We demonstrate here a new enzymatic assay which is 100-fold more sensitive than previous assays and can detect as little as 1.0 pmol of rhizobitoxine. The assay is based on the inhibition of Salmonella typhimurium beta-cystathionase by rhizobitoxine. Interestingly, beta-cystathionase from Bradyrhizobium japonicum is insensitive to rhizobitoxine at concentrations lower than 75 microM.
Asunto(s)
Propanolaminas/análisis , Pseudomonas/análisis , Rhizobiaceae/análisis , Liasas/antagonistas & inhibidores , Propanolaminas/farmacología , Salmonella typhimurium/enzimologíaRESUMEN
Lipopolysaccharides (LPSs) from a number of bacteria belonging to the alpha-2 subgroup of the class Proteobacteria were screened for the presence of 27-hydroxy-octacosanoic acid (27-OH-28:0). With few exceptions, most of the bacteria contained 27-OH-28:0 in their lipid A fractions. In addition, some of the bacteria contained other n-2-hydroxylated long-chain fatty acids hitherto not reported. The distribution of 27-OH-28:0 was restricted to the alpha-2 subgroup. LPSs from members of the other subgroups (the beta and gamma subgroups), including some well-characterized enterobacterial LPSs, were devoid of 27-OH-28:0. Our results indicate that the presence of n-2-hydroxylated long-chain fatty acids in LPSs might be used as a chemophylogenetical marker.
Asunto(s)
Hidroxiácidos/análisis , Lipopolisacáridos/análisis , Filogenia , Rhizobiaceae/análisis , Espectrometría de Masas , Estructura Molecular , Rhizobiaceae/clasificaciónRESUMEN
Lipopolysaccharides (LPSs) isolated from several strains of Rhizobium, Bradyrhizobium, Agrobacterium, and Azorhizobium were screened for the presence of 27-hydroxyoctacosanoic acid. The LPSs from all strains, with the exception of Azorhizobium caulinodans, contained various amounts of this long-chain hydroxy fatty acid in the lipid A fractions. Analysis of the lipid A sugars revealed three types of backbones: those containing glucosamine (as found in Rhizobium meliloti and Rhizobium fredii), those containing glucosamine and galacturonic acid (as found in Rhizobium leguminosarum bv. phaseoli, trifolii, and viciae), and those containing 2,3-diamino-2,3-dideoxyglucose either alone or in combination with glucosamine (as found in Bradyrhizobium japonicum and Bradyrhizobium sp. [Lupinus] strain DSM 30140). The distribution of 27-hydroxyoctacosanoic acid as well as analysis of lipid A backbone sugars revealed the taxonomic relatedness of various strains of the Rhizobiaceae.
Asunto(s)
Hidroxiácidos/química , Lípido A/química , Lipopolisacáridos/química , Rhizobiaceae/análisis , Ácidos Grasos/análisisRESUMEN
We report the initial characterization of the cell-associated oligosaccharides produced by four Bradyrhizobium strains: Bradyrhizobium japonicum USDA 110, USDA 94, and ATCC 10324 and Bradyrhizobium sp. strain 32H1. The cell-associated oligosaccharides of these strains were found to be composed solely of glucose and were predominantly smaller than the cyclic beta-1,2-glucans produced by Agrobacterium and Rhizobium species. Linkage studies and nuclear magnetic resonance analyses demonstrated that the bradyrhizobial glucans are linked primarily by beta-1,6 and beta-1,3 glycosidic bonds. Thus, the bradyrhizobia appear to synthesize cell-associated oligosaccharides of structural character substantially different from that of the cyclic beta-1,2-glucans produced by Agrobacterium and Rhizobium species.
Asunto(s)
Oligosacáridos/análisis , Rhizobiaceae/análisis , Glucanos/análisis , Espectroscopía de Resonancia Magnética , Rhizobium/análisisRESUMEN
Lipid A's from two Bradyrhizobium species and from the phylogenetically closely related species "Pseudomonas carboxydovorans" were found to contain 2,3-diamino-2,3-dideoxy-glucose as lipid A backbone sugar. In contrast, three representatives of the genus Rhizobium, as well as the phylogenetically related species Agrobacterium tumefaciens, contain solely glucosamine as lipid A backbone sugar. These findings support independent studies on the phylogenetical relatedness based on 16S rRNA-data of the genus Bradyrhizobium with "Pseudomonas carboxydovorans" and Rhodopseudomonas palustris, which form a tight phylogenetical cluster and which all contain the 2,3-diamino-2,3-dideoxy-glucose-containing lipid A. The relatedness of these species to the glucosamine-containing species of the genus Rhizobium and to Agrobacterium tumefaciens is rather distant as documented by 16S rRNA studies.
Asunto(s)
Glucosamina/análogos & derivados , Lípido A/análisis , Lipopolisacáridos/análisis , Pseudomonas/análisis , Rhizobiaceae/análisis , Electroforesis en Gel de Poliacrilamida , Glucosamina/análisis , Filogenia , Pseudomonas/clasificación , Pseudomonas/crecimiento & desarrollo , Rhizobiaceae/clasificación , Rhizobiaceae/crecimiento & desarrollo , Rhizobium/análisis , Rhizobium/clasificación , Rhizobium/crecimiento & desarrolloRESUMEN
The DNA-binding HU-type proteins from several species of Rhizobiaceae including Rhizobium meliloti, two strains of Rhizobium leguminosarum with highly different phenotypic characters and Agrobacterium tumefaciens, were characterized and their amino acid sequences were determined. HU-type proteins isolated from R. leguminosarum L18 and A. tumefaciens are identical and show slight differences with the R. meliloti HU-type protein. On the other hand the R. leguminosarum L53 HU-type protein is quite different from the proteins cited above; several amino acid substitutions encountered in this protein result in significant changes in the folding of the polypeptide chain. The biochemical characteristics of these proteins are in good agreement with the respective position of these bacteria in the phylogeny determined by numerical taxonomy.
Asunto(s)
Proteínas Bacterianas/aislamiento & purificación , Proteínas de Unión al ADN/aislamiento & purificación , Rhizobiaceae/análisis , Secuencia de Aminoácidos , Proteínas Bacterianas/clasificación , Fenómenos Químicos , Química , Proteínas de Unión al ADN/clasificación , Electroforesis en Gel de Poliacrilamida , Terminología como AsuntoRESUMEN
The DNA-binding HU-type proteins have been isolated from two very different strains of Rhizobiaceae : Agrobacterium tumefaciens and Rhizobium japonicum. These proteins have been called HAt and HRj respectively. Their electrophoretic mobility on polyacrylamide gel, amino acid composition and crossed immunoreactivity have been compared to that of the homologous protein isolated from Rhizobium meliloti: the protein HRm . The proteins HAt and HRm show close similarities whereas the protein HRj differs markedly from the two others. The physico-chemical characteristics of the HU-type proteins from these Rhizobiaceae are in good agreement with the respective position of these bacteria in the taxonomy.