We report here the whole-genome sequences of 14 strains of Bradyrhizobium canariense, isolated from root nodules of Lupinus microanthus and Lupinus angustifolius, and 1 strain of Bradyrhizobium japonicum isolated from root nodules from Lupinus angustifolius in Algeria. These sequences add to the known diversity of this agronomically important genus.
Phenotypic characteristics of 37 rhizobia strains isolated from root nodules of Medicago ciliaris L. growing in soils collected from Zerizer (North Eastern Algeria) were studied. Tolerance to salinity, high temperatures, acid and alkaline pHs, drought and to antibiotics as well as symbiotic and cultural characteristics allowed the description of a wide physiological diversity among tested isolates. Thirteen (13) isolates from the total could grow at 45°C. Only six isolates grew at 4% NaCl. Furthermore, the isolates which showed tolerance to salinity stress also showed tolerance to water stress, indicating direct relationships between these two physiological pathways. High salt and water stress tolerant strains were isolated and tested for their ability to biological nitrogen fixation. However, seven isolates were categorized into Agrobacterium.
Forty rhizobial strains were isolated from root nodules of Medicago littoralis Rhode and Melilotus indicus (L.) harvested from the sandy soils of Touggourt’s oases in the Oued Righ Valley, Algerian Sahara. The isolates were studied for their cultural, biochemical and symbiotic effectiveness. All of them were fast-growing bacteria; utilized a wide range of carbon sources, produced abundant extracellular polysaccharides, tolerated high concentrations of NaCl (up to 2.5 %), grew at temperatures between 28 and 45 °C and at pH values between 4.5 and 9. The isolates were sensitive to the antibiotics kanamycin, tetracycline and rifampicin but showed resistance to neomycin and erythromycin. All the isolates induced the formation of effective nodules on their host plants. On the basis of the physiological, biochemical and symbiotic effectiveness, we selected six strains MD05, MD09, MD12, ML08, ML17 and ML22 for genotypic characterization. Phylogenetic analysis of the selected strains based on 16S ribosomal RNA gene showed that these strains of bacteria were affiliated to the Ensifer meliloti group
In this study, we evaluated the ability of rhizobacteria isolated from Trifolium sp. nodules growing on a Pb/Zn mine site to produce plant growth-promoting substances, such as siderophores, extracellular enzymes, antifungal substances, their capacity to solubilize phosphate, and also their tolerance to heavy metals and salinity. Overall, the results demonstrated that bacterial isolates showed an ability to produce multiple important plant growth-promoting traits, with remarkable ability to grow up to 20% salt concentration and resist to high levels of heavy metals up to 1300 mg/L Pb++, 1200 mg/L Zn++, 1000 mg/L Ni++, 1000 mg/L Cd++, 500 mg/L Cu++, 400 mg/L Co++, and 50 mg/L CrVI+. The order of resistance of isolates to heavy metals was reduced as follows: Pb++ > Zn++ > Ni++ > Cd++ > Cu++ > Co++ > CrVI+. All isolates had multiple metal-resistant abilities; however, the existence of the pbrA, czcD, and nccA genes responsible for resistance to Pb++, Zn++, Cd++, Co++, and Ni++, respectively, was determined by PCR and were detected only on Cupriavidus paucula RSCup01. Our results also showed that the plant growth-promoting rhizobacteria strains screened in the present study could be used as a potential inoculant for the improvement of phytoremediation in heavy metal-polluted soils.
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