Isolation and characterization of an extremely heavy metal tolerant Sinorhizobium meliloti, utilizable for reclamation of polluted soils
Journal Title: Journal of Biodiversity and Environmental Sciences (JBES) - Year 2015, Vol 6, Issue 2
Abstract
Soil heavy metals (HMs) have deleterious effects on Sinorhizobia and their symbiotic relationship with Legumes. Consequently, isolating HMs resistant strains and using them as inoculums in polluted soils is crucially important. In the present study, the effects of cadmium, lead and zinc on viability and nitrogen fixing potential of several native Sinorhizobium meliloti strains isolated from HMs polluted soils of Zanjan province- Iran was assessed. In this regard, several S. meliloti stains were isolated from alfalfa root nodules and their nitrogen fixation efficiencies were evaluated and compared based on symbiosis effectiveness and alfalfa shoot dry weights. Selective media containing different amounts of cadmium, lead and zinc were utilized to evaluate the tolerance rates of the isolate. Subsequently, the most HMs tolerant strains with high nitrogen fixation capability were evaluated and selected in pot experiments. Five HMS tolerant S. meliloti strains were selected and inoculated in culture media containing five different concentrations of cadmium, lead and zinc. S41 was recognized as the most HMs tolerant isolate with a symbiotic effectiveness of 139%. PCR amplification and sequencing of 16S-23S rRNA Intergenic Spacer Region was employed for molecular identification of this isolate which could significantly decrease the need for exogenous nitrogen.
Authors and Affiliations
Seyyed Mahdi Hosseinian, Shiva Khaledzadeh, Sara Nosrati, Ahmad Golchin, Esmail Memar-Kochehbagh
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