Characterization of Root-Nodule Bacteria Isolated from Hedysarum spinosissimum L, Growing in Mining Sites of Northeastern Region of Morocco

Abstract

expensive and harmful to soil integrity and microbial diversity [3,4]. Phytoremediation appears as a good alternative as plants can indeed bio-concentrate (phytoextraction) as well as bio-immobilize (phytostabilization) toxic metals through in situ rhizospheric processes [1,2]. However, mining sites in semi-arid areas are characterized by low vegetation cover due to the unfavorable effects of a combination of environmental factors, including metals toxicity, nutrient deficiency, poor soil structure and low water retention [5,6], thus, the development of a vegetative cover in these environments is a challenge. Recently, several studies have shown that the combination of plant-associated bacteria in phytoremediation may lead to promising results, in particular the group of plant growth promoting bacteria [7,8]. This approach is furthermore perceived as cost-effective, eco-friendly, and with good public acceptance [2]. The choice of bacteria is usually based on their potential to produce phytohormones such as IAA, gibberellins and cytokinins that directly promote roots and plant growth [9]. Other bacteria can synthesize organic chelators (siderophores) to acquire iron [10] that will play a positive role in plant nutrition; some have great potential for phosphate solubilization or possess ACC deaminase activity [11] while others are able to fix nitrogen [1] or provide protection against viral diseases [12]. In addition, microorganisms can be implicated directly in metal mobilization/ immobilization, by changing the metal bioavailability, solubility and toxicity by different mechanisms including alteration of soil pH, releasing of chelators (organic acids, biosurfactants, siderophores, polymeric substances or glycoprotein, etc), metal biosorption or by oxidation/ reduction reactions [4,13]. The use of plants for the remediation of contaminated soils by heavy metals obviously also depends on the plant species, and on its anatomical, physiological and molecular characteristics

Chromium Hyper-Tolerant Bacillus sp. MH778713 Assists Phytoremediation of Heavy Metals by Mesquite Trees (Prosopis laevigata)

“…Although Bacillus has not been described as legume symbiont, several Bacillus strains have been identified as endophytic bacteria. They have been isolated from a variety of plants, including legume plants as Medicago polymorPha (Chinnaswamy et al, 2018), Dalbergia odorifera (Lu et al, 2017), Glycine max (Hong et al, 2007), Cajanus cajan (Rajendran et al, 2007) , Hedysarum spinosissimum (Sbabou et al, 2016) and Prosopis species. Bacteria belonging to genus Bacillus have been isolated from the endosphere and rhizosphere of Prosopis juliflora (Khan et al, 2014; Abdelmoteleb et al, 2017) and Prosopis farcta nodules (Fterich et al, 2011).…”

BradyrhizobiumandPseudomonasstrains obtained from coal-mining areas nodulate and promote the growth ofCalopogonium muconoidesplants used in the reclamation of degraded areas

“…These same limitations can also be found in the work of Sbabou et al . (), who described species of the three subclasses (α, β and γ‐proteobacteria) present in Hedysarum nodules. From that data it can be inferred only that the bacteria are endophytic to the nodules, but not necessarily that they have the capacity to form the nodules.…”

Role of microorganisms in rehabilitation of mining sites, focus on Sub Saharan African countries

“…Similar study conducted with Bradyrhizobium strain isolated from greengram nodules (Vigna radiata), showed similar results with a decrease of the concentration of nickel and zinc in plant organs and plant growth promoting activities. Sbabou et al, 2016 isolated two bacteria from the nodules of the legume Hedysarum spinosissimum growing in metal contaminated soils in Morocco and showed that their inoculation promoted host plant growth and suppressed Zn toxicity symptoms in plants, enhancing their phytostabilization potential.…”