Prospecting metal-resistant plant-growth promoting rhizobacteria for rhizoremediation of metal contaminated estuaries using Spartina densiflora

Abstract

In the salt marshes of the joint estuary of Tinto and Odiel rivers (SW Spain), one of the most polluted areas by heavy metals in the world, Spartina densiflora grows on sediments with high concentrations of heavy metals. Furthermore, this species has shown to be useful for phytoremediation. The total bacterial population of the rhizosphere of S. densiflora grown in two estuaries with different levels of metal contamination was analyzed by PCR denaturing gradient gel electrophoresis. Results suggested that soil contamination influences bacterial population in a greater extent than the presence of the plant. Twenty-two different cultivable bacterial strains were isolated from the rhizosphere of S. densiflora grown in the Tinto river estuary. Seventy percent of the strains showed one or more plant growth-promoting (PGP) properties, including phosphate solubilization and siderophores or indolacetic acid production, besides a high resistance towards Cu. A bacterial consortium with PGP properties and very high multiresistance to heavy metals, composed by Aeromonas aquariorum SDT13, Pseudomonas composti SDT3, and Bacillus sp. SDT14, was selected for further experiments. This consortium was able to two-fold increase seed germination and to protect seeds against fungal contamination, suggesting that it could facilitate the establishment of the plant in polluted estuaries.

Deciphering the role of plant growth-promoting rhizobacteria in the tolerance of the invasive cordgrass Spartina densiflora to physicochemical properties of salt-marsh soils

“…SDT14, were isolated from the rhizosphere of S. densiflora grown in the Tinto River estuary (Andrades-Moreno et al 2014). They represent the bestperforming strains of all the isolates studied.…”

“…They represent the bestperforming strains of all the isolates studied. Thus, they were included in a consortium in order to combine high resistance to several metals and plant growth promoting (PGP) properties, including production of siderophores and indoleacetic acid (IAA) and phosphate solubilisation (Andrades-Moreno et al 2014).…”

“…This species is a facultative halophyte that has demonstrated a remarkable physiological and morphological versatility, which enables it to withstand a wide scope of salinity, tidal submergence, soil types, drainage and nutrient availability (Mateos-Naranjo et al 2007). Recently, Andrades-Moreno et al (2014) isolated 22 different cultivable bacterial strains from the rhizosphere of S. densiflora growing in the Tinto river estuary (SW Spain). Seventy percent of the strains proved to have one or more plant growth promoting (PGP) properties, including phosphate solubilisation and production of siderophores or indolacetic acid (IAA).…”

“…Seventy percent of the strains proved to have one or more plant growth promoting (PGP) properties, including phosphate solubilisation and production of siderophores or indolacetic acid (IAA). Also, Andrades-Moreno et al (2014) in a germination experiment with S. densiflora using a selected bacterial consortium concluded that it was able to double seed germination and to protect seeds against fungal contamination, suggesting that the bacterial consortium could facilitate the establishment of the plant in estuaries. In line with these findings, in the present study we hypothesized that bacteria from the rhizosphere of S. densiflora with PGP properties might play a key role in the high ecological and physiological versatility shown by this species to the physicochemical properties of marsh soils.…”

Effect of Enterobacter sp. CS2 and EDTA on the Phytoremediation of Ni-contaminated Soil by Impatiens balsamina

“…The plant growth-promoting rhizobacteria (PGPR) improve plant growth by phosphate solubilization, auxin synthesis, and siderophores production [12][13]. PGPR may synthesize biosurfactants for the desorbtion of soil-adsorbed metal [14][15].…”