Phenotypic, genetic and symbiotic characterization of Erythrina velutina rhizobia from Caatinga dry forest

Abstract Erythrina velutina ("mulungu") is a legume tree from Caatinga that associates with rhizobia but the diversity and symbiotic ability of "mulungu" rhizobia are poorly understood. The aim of this study was to characterize "mulungu" rhizobia from Caatinga. Bacteria were obteined from Serra Talhada and Caruaru in Caatinga under natural regeneration. The bacteria were evaluated to the amplification of nifH and nodC and to metabolic characteristics. Ten selected bacteria identified by 16S rRNA sequences. They were tested in vitro to NaCl and temperature tolerance, auxin production and calcium phosphate solubilization. The symbiotic ability were assessed in an greenhouse experiment. A total of 32 bacteria were obtained and 17 amplified both symbiotic genes. The bacteria showed a high variable metabolic profile. Bradyrhizobium (6), Rhizobium (3) and Paraburkholderia (1) were identified, differing from their geographic origin. The isolates grew up to 45 °C to 0.51 mol L-1 of NaCl. Bacteria which produced more auxin in the medium with l-tryptophan and two Rhizobium and one Bradyrhizobium were phosphate solubilizers. All bacteria nodulated and ESA 90 (Rhizobium sp.) plus ESA 96 (Paraburkholderia sp.) were more efficient symbiotically. Diverse and efficient rhizobia inhabit the soils of Caatinga dry forests, with the bacterial differentiation by the sampling sites.

Phenotypic, genetic and symbiotic characterization of Erythrina velutina rhizobia from Caatinga dry forest.

Erythrina velutina ("mulungu") is a legume tree from Caatinga that associates with rhizobia but the diversity and symbiotic ability of "mulungu" rhizobia are poorly understood. The aim of this study was to characterize "mulungu" rhizobia from Caatinga. Bacteria were obteined from Serra Talhada and Caruaru in Caatinga under natural regeneration. The bacteria were evaluated to the amplification of nifH and nodC and to metabolic characteristics. Ten selected bacteria identified by 16S rRNA sequences. They were tested in vitro to NaCl and temperature tolerance, auxin production and calcium phosphate solubilization. The symbiotic ability were assessed in an greenhouse experiment. A total of 32 bacteria were obtained and 17 amplified both symbiotic genes. The bacteria showed a high variable metabolic profile. Bradyrhizobium (6), Rhizobium (3) and Paraburkholderia (1) were identified, differing from their geographic origin. The isolates grew up to 45°C to 0.51molL-1 of NaCl. Bacteria which produced more auxin in the medium with l-tryptophan and two Rhizobium and one Bradyrhizobium were phosphate solubilizers. All bacteria nodulated and ESA 90 (Rhizobium sp.) plus ESA 96 (Paraburkholderia sp.) were more efficient symbiotically. Diverse and efficient rhizobia inhabit the soils of Caatinga dry forests, with the bacterial differentiation by the sampling sites.

Antiangiogenetic effects of anthranoids from Alternaria sp., an endophytic fungus in a Thai medicinal plant Erythrina variegata.

Endophytic fungi are known as a prolific source for the discovery of structurally interesting and biologically active secondary metabolites, some of which are promising candidates for drug development. In the present study, three anthranoids were isolated from an Alternaria sp. endophytic fungus and evaluated for their antiangiogenic activity in a rat aortic sprouting assay, an ex vivo model of angiogenesis. Of these three compounds, altersolanol (2) was further characterized and found to show a promising activity in ex vivo, in vitro and in vivo angiogenesis asssays. Using human umbilical vein endothelial cells as an in vitro model, the angiogenic effect of 2 was found to occur via suppression of all three main functions of endothelial cells, namely proliferation, tube formation and migration.

Phylogenetically diverse groups of Bradyrhizobium isolated from nodules of Crotalaria spp., Indigofera spp., Erythrina brucei and Glycine max growing in Ethiopia.

Ethiopian Bradyrhizobium strains isolated from root nodules of Crotalaria spp., Indigofera spp., Erythina brucei and soybean (Glycine max) represented genetically diverse phylogenetic groups of the genus Bradyrhizobium. Strains were characterized using the amplified fragment length polymorphism fingerprinting technique (AFLP) and multilocus sequence analysis (MLSA) of core and symbiotic genes. Based on phylogenetic analyses of concatenated recA-glnII-rpoB-16S rRNA genes sequences, Bradyrhizobium strains were distributed into fifteen phylogenetic groups under B. japonicum and B. elkanii super clades. Some of the isolates belonged to the species B. yuanmingense, B. elkanii and B. japonicum type I. However, the majority of the isolates represented unnamed Bradyrhizobium genospecies and of these, two unique lineages that most likely represent novel Bradyrhizobium species were identified among Ethiopian strains. The nodulation nodA gene sequence analysis revealed that all Ethiopian Bradyrhizobium isolates belonged to nodA sub-clade III.3. Strains were further classified into 14 groups together with strains from Africa, as well as some originating from the other tropical and subtropics regions. Strains were also clustered into 14 groups in nodY/K phylogeny similarly to the nodA tree. The nifH phylogenies of the Ethiopian Bradyrhizobium were generally also congruent with the nodA gene phylogeny, supporting the monophyletic origin of the symbiotic genes in Bradyrhizobium. The phylogenies of nodA and nifH genes were also partially congruent with that inferred from the concatenated core genes sequences, reflecting that the strains obtained their symbiotic genes vertically from their ancestor as well as horizontally from more distantly related Bradyrhizobium species.

Antimicrobial isoflavonoids from Erythrina crista galli infected with Phomopsis sp.

The isoflavonoids coumestrol, genistein and daidzein have been isolated and identified by bioassay-guided fractionation from the acetone extract of Erythrina crista galli young twigs infected with Phomopsis sp. These compounds showed antimicrobial activity against Bacillus brevis (MIC values 16.3, 64.8 and 137.8 microM, respectively). This is the first time that coumestrol, besides lutein and n-nonacosane, are reported in this species.

Phomol, a new antiinflammatory metabolite from an endophyte of the medicinal plant Erythrina crista-galli.

Phomol (1), a novel antibiotic, was isolated from fermentations of a Phomopsis species in the course of a screening of endophytic fungi from the medicinal plant Erythrina crista-galli. For this Argentinean leguminosa antiinflammatory and neuroleptic activities have been described. The compound exhibits antifungal, antibacterial and weak cytotoxic acticity. The antiinflammatory activity was tested in different reporter gene assays (TNF-alpha, STAT1/STAT2 and NF-kappaB) and in an ear edema model in mice. In the reporter gene assays 1 exhibited no activity, whereas 1 showed interesting antiinflammatory activity in the mouse ear assay. The compound is a polyketide lactone and its structure was elucidated by spectroscopic methods.

Metabolic and genomic diversity of rhizobia isolated from field standing native and exotic woody legumes in southern Ethiopia.

Eighty-seven rhizobial strains isolated from root nodules of field standing native and exotic woody legumes in southern Ethiopia were characterized using the Biolog method and AFLP fingerprinting technique. Cluster analysis of the metabolic and genomic fingerprints revealed 18 and 25 groups, respectively, demonstrating considerable diversity in rhizobial population indigenous to Ethiopian soils. While 25 strains (29%) were linked to members of Agrobacterium, Bradyrhizobium, Mesorhizobium, Rhizobium or Sinorhizobium, the bulk of the strains formed several distinct groups in both methods and did not relate to reference species included in the study. In contrast to exotic species which formed symbiosis with strains of only one specific genomic group, indigenous host species nodulated by metabolically and genomically diverse groups. The results in this study support the view, that long-term association between the symbionts allows gradual differentiation and diversity in compatible rhizobial population resident in native soils. Lack of significant metabolic and genomic relatedness to the reference strains in our results suggested that test strains in our collection probably included 'unique' types, which belong to several yet undefined rhizobial species.

Samsonia erythrinae gen. nov., sp. nov., isolated from bark necrotic lesions of Erythrina sp., and discrimination of plant-pathogenic Enterobacteriaceae by phenotypic features.

Bacterial strains isolated from diseased erythrina (Erythrina sp.) trees in Martinique (French West Indies) were studied using phenotypic tests, 16S rDNA sequence analysis and DNA-DNA hybridization. Numerical analysis of phenotypic characteristics showed that these strains formed an homogeneous phenon among plant-pathogenic Enterobacteriaceae, and gave useful and updated information for the identification of these bacteria. Results of DNA-DNA hybridization indicated that strains from erythrina belonged to a discrete genomospecies (89-100% hybridization) and had low levels of DNA relatedness (2-33% hybridization) with reference strains of phytopathogenic Erwinia, Brenneria, Pectobacterium, Pantoea and Enterobacter species. 16S rDNA sequence analysis using three different methods revealed that the position of strain CFBP 5236T isolated from erythrina was variable in the different trees, so that strains from erythrina could not be assigned to any recognized genus. It is proposed that these strains are included in a new genus, Samsonia. The name Samsonia erythrinae is proposed for the new species. The G+C content of the DNA of the type strain, CFBP 5236T (= ICMP 13937T), is 57.0 mol%.