Improvement of plant growth and nickel uptake by nickel resistant-plant-growth promoting bacteria

Abstract

In this study, among a collection of Ni-resistant bacterial strains isolated from the rhizosphere of Alyssum serpyllifolium and Phleum phleoides grown on serpentine soil, five plant growth-promoting bacteria (PGPB) were selected based on their ability to utilize 1-aminocyclopropane-1-carboxylate (ACC) as the sole N source and promote seedling growth. All of the strains tested positive for indole-3-acetic acid (IAA) production and phosphate solubilization. In addition, four of the strains exhibited significant levels of siderophores production. Further, the efficiency of PGPB in enhancing Ni solubilization in soils was analyzed. Compared with control treatment, inoculation of PGPB strains significantly increased the concentrations of bioavailable Ni. Furthermore, a pot experiment was conducted to elucidate the effects of inoculating Ni-resistant PGPB on the plant growth and the uptake of Ni by Brassica juncea and B. oxyrrhina in soil contaminated with 450 mg kg(-1) Ni. Psychrobacter sp. SRA2 significantly increased the fresh (351%) and dry biomass (285%) of the B. juncea test plants (p<0.05), whereas Psychrobacter sp. SRA1 and Bacillus cereus SRA10 significantly increased the accumulation of Ni in the root and shoot tissues of B. juncea compared with non-inoculated controls. This result indicates that the strains SRA1 and SRA10 facilitated the release of Ni from the non-soluble phases in the soil, thus enhancing the availability of Ni to plants. A significant increase, greater than that of the control, was also noted for growth parameters of the B. oxyrrhina test plants when the seeds were treated with strain SRA2. This effect can be attributed to the utilization of ACC, solubilization of phosphate and production of IAA. The results of the study revealed that the inoculation of Ni mobilizing strains Psychrobacter sp. SRA1 and B. cereus SRA10 increases the efficiency of phytoextraction directly by enhancing the metal accumulation in plant tissues and the efficient PGPB, Psychrobacter sp. SRA2 increases indirectly by promoting the growth of B. juncea and B. oxyrrhina.

Phytoextraction of heavy metal polluted soils using Sedum plumbizincicola inoculated with metal mobilizing Phyllobacterium myrsinacearum RC6b

“…Compared with non-inoculated control treatment,inoculation of RC6b for 7 d, significantly increased the concentrations of water soluble Cd, Zn and Pb in soil by 16.7-, 4.6-and 5.7-fold, respectively. These results are consistent with those of Jiang et al (2008) and Rajkumar et al (2008) and Ma et al (2009), they found an increase in metal concentrations (Ni, Cu, Zn, Cd and Pb) in water soluble fractions in the presence of metal mobilizing bacteria. The observed increase in the concentrations of water soluble metals in this study could be attributed to the effects of microbial metabolites/actions such as altering soil pH, release of organic acids, siderophores and oxidation/reduction reactions (Rajkumar et al, 2012(Rajkumar et al, , 2013.…”

“…The bacterial growth was monitored by measuring the OD at 600 nm. Further, the ACC deaminase activity was determined as described by Ma et al (2009). Siderophore production by metal mobilizing strain was detected by the method of Schwyn and Neilands (1987) using chrome azurol S (CAS) agar.…”

“…Plant root and shoot length, fresh and dry weight were measured, respectively. The accumulation of metals (Cd, Zn, and Pb) in root and shoot system was quantified as described by Ma et al (2009).…”

“…It has been demonstrated that the inoculation of plants with metalresistant plant growth-promoting rhizobacteria (PGPR) play an important role in improving the efficiency of heavy metal phytoremediation Rajkumar et al, 2012). PGPR such as Azospirillum, Azotobacter, Achromobacter, Bacillus, Burkholderia, Gluconacetobacter, Pseudomonas and Serratia, have been known to improve plant growth through various mechanisms like production of phytohormones, siderophores and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, and solubilization of mineral nutrients (Rajkumar et al, 2008;Sheng et al, 2008;Ma et al, 2009).…”

Comparative plant growth promoting traits and distribution of rhizobacteria associated with heavy metals in contaminated soils

“…The addition of certain metal resistant microorganisms like Psychrobacter sp. SRA1, Bacillus cereus SRA10, Bacillus weihenstephanensis SRP12, Sphingomonas macrogoltabidus and Microbacterium liquefaciens, can affect the trace metal mobility and availability to the plants through release of chelating agents, acidification, phosphate solubilization and redox changes (Abou-Shanab et al, 2003;Idris et al, 2004;Ma et al, 2009).…”