Characterization of efficient plant-growth-promoting bacteria isolated from Sulla coronaria resistant to cadmium and to other heavy metals

Abstract

The inoculation of plants with plant-growth-promoting rhizobacteria has become a priority in the phytoremediation of heavy-metal-contaminated soils. A total of 82 bacteria were isolated from Sulla coronaria root nodules cultivated on four soil samples differently contaminated by heavy metals. The phenotypic characterization of these isolates demonstrated an increased tolerance to cadmium reaching 4.1mM, and to other metals, including Zn, Cu and Ni. Polymerase Chain Reaction/Restriction Fragment Length Polymorphism (PCR/RFLP) analysis showed a large diversity represented by genera related to Agrobacterium sp., R. leguminosarum, Sinorhizobium sp., Pseudomonas sp., and Rhizobium sp. Their symbiotic effectiveness was evaluated by nodulation tests. Taking into consideration efficiency and cadmium tolerance, four isolates were chosen; their 16SrRNA gene sequence showed that they belonged to Pseudomonas sp. and the Rhizobium sullae. The selected consortium of soil bacteria had the ability to produce plant-growth-promoting substances such as indole acetic acid and siderophore. The intracellular Cd accumulation was enhanced by increasing the time of incubation of the four soil bacteria cultivated in a medium supplemented with 0.1mM Cd. The existence of a cadmium-resistant gene was confirmed by PCR. These results suggested that Sulla coronaria in symbiosis with the consortium of plant-growth-promoting rhizobacteria (PGPR) could be useful in the phytoremediation of cadmium-contaminated soils.

Biodegradation of Phenanthrene and Heavy Metal Removal by Acid-Tolerant Burkholderia fungorum FM-2

“…(strain I10). Furthermore, intracellular Cd (II) bioaccumulation was found to be greater than that in the cell wall, demonstrating that Cd (II) bioaccumulation was related to cell growth and/or increased biomass (Chiboub et al, 2016). The Cd (II) bioaccumulation by strain FM-2 demonstrated in the present work is therefore consistent with previous reports.…”

“…Cultures were incubated at 25°C with shaking at 200 rpm for 1, 3, 5, and 7 days. As described previously (Chiboub et al, 2016) with some modifications, cultures were centrifuged (8,000 rpm for 5 min at 4°C) and pellets were washed three times with sterile distilled water to remove free heavy metal ions. Pellets were then treated with 10 mM sterile EDTA at 25°C with agitation at 200 rpm for 30 min.…”

Screening of plant growth promoting traits in heavy metals resistant bacteria: Prospects in phytoremediation

“…The phytohormone production by PGPB is shown to play a key role in plant–bacterial interactions and plant growth in contaminated soils by heavy metals [53]. In fact, many heavy metals resistant bacteria were capable of producing phytohormones such as auxin IAA even under stress conditions [54], [55]. Thus, the observed plant growth promotion under Pb stress after inoculation of plant with P. fluorescens was attributed to bacterial IAA production and excretion [56].…”

Inoculation of Sinorhizobium saheli YH1 Leads to Reduced Metal Uptake for Leucaena leucocephala Grown in Mine Tailings and Metal-Polluted Soils

“…The production of IAA by strain YH1 is higher (>100 μg ml −1 ) than most rhizobial stains previously reported and can be considered as an IAA-overproducer (Chiboub et al, 2016; Yu et al, 2017). It is observed that negative impact of metal accumulation inside plant tissues could be mitigated by the application of IAA (Nadeem et al, 2015).…”