Characterization of a phenol-degrading bacterium isolated from an industrial effluent and its potential application for bioremediation

The use of native microorganisms is a useful strategy for phenol bioremediation. In the present work, a bacterial strain, named RTE1.4, was isolated from effluents of a chemical industry. The strain was able to grow at high concentrations of phenol and its derivatives, such as guaiacol, 2,4-dichlorophenol and pentachlorophenol, as well as in a medium containing industrial effluents. This bacterium was identified as Acinetobacter sp. using morphological, physiological, biochemical and 16S rRNA gene analysis. Acinetobacter sp. RTE1.4 degraded phenol (200 to 600 mg/L) at wide pH range and temperature (5-9 and 25-37°C, respectively) demonstrating high adaptation ability to different conditions. The strain would metabolize phenol by the ortho-pathway since catechol 1,2-dioxygenase activity was detected. When bacteria were grown in medium containing phenol, an altered whole-cell protein pattern was observed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), with the lack of some low-molecular mass polypeptides and an increase in the relative abundance of high-molecular mass proteins after treatment. Considering that the use of native strains in bioremediation studies shows several ecological advantages and that the studied bacterium showed high tolerance and biodegradation capabilities, Acinetobacter sp. RTE1.4 could be an appropriate microorganism for improving bioremediation and biotreatment of areas polluted with phenol and/or some of its derivatives. Moreover, the establishment of the optimal growth conditions (pH, temperature, concentration of the pollutant) would provide baseline data for bulk production of the strain and its use in bioremediation processes. © 2013 Copyright Taylor and Francis Group, LLC.Fil: Paisio, Cintia Elizabeth. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Biotecnología Ambiental y Salud - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Biotecnología Ambiental y Salud; ArgentinaFil: Talano, Melina Andrea. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Biología Molecular. Sección Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: González, Paola Solange. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Biología Molecular. Sección Química Biológica; ArgentinaFil: Pajuelo Domínguez, Eloisa. Universidad de Sevilla; EspañaFil: Agostini, Elizabeth. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Biotecnología Ambiental y Salud - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Biotecnología Ambiental y Salud; Argentin

Use of native plants and their associated bacteria rhizobiomes to remediate-restore Draa Sfar and Kettara mining sites, Morocco

International audienceSoil and mine tailings are unreceptive to plant growth representing an imminent threat to the environment and resource sustainability. Using indigenous plants and their associated rhizobacteria to restore mining sites would be an eco-friendly solution to mitigate soil-metal toxicity. Soil prospection from Draa Sfar and Kettara mining sites in Morocco was carried out during different seasons for native plant sampling and rhizobacteria screening. The sites have been colonized by fifteen tolerant plant species having different capacities to accumulate Cu, Zn, and P in their shoots/root systems. In Draa Sfar mine, Suaeda vera J.F. Gmel., Sarcocornia fruticosa (L.) A.J. Scott., and Frankenia corymbosa Desf. accumulated mainly Cu (more than 90 mg kg−1), Atriplex halimus L. accumulated Zn (mg kg−1), and Frankenia corymbosa Desf. accumulated Pb (14 mg kg−1). As for Kettara mine, Aizoon canariense L. mainly accumulated Zn (270 mg kg−1), whereas Forsskalea tenacissima L. was the best shoot Cu accumulator with up to 50 mg kg−1, whereas Cu accumulation in roots was 21 mg kg−1. The bacterial screening revealed the strains’ abilities to tolerate heavy metals up to 50 mg kg−1 Cu, 250 mg kg−1 Pb, and 150 mg kg−1 Zn. Isolated strains belonged mainly to Bacillaceae (73.33%) and Pseudomonadaceae (10%) and expressed different plant growth–promoting traits, alongside their antifungal activity. Results from this study will provide an insight into the ability of native plants and their associated rhizobacteria to serve as a basis for remediation-restoration strategies

Engineering Copper Hyperaccumulation in Plants by Expressing a Prokaryotic <i>copC</i> Gene

In this work, engineering Cu-hyperaccumulation in plants was approached. First, the <i>copC</i> gene from Pseudomonas sp. Az13, encoding a periplasmic Cu-binding protein, was expressed in Arabidopsis thaliana driven by the <i>CaMV35S</i> promoter (transgenic lines 35S-copC). 35S-copC lines showed up to 5-fold increased Cu accumulation in roots (up to 2000 μg Cu. g^–1) and shoots (up to 400 μg Cu. g^–1), compared to untransformed plants, over the limits established for Cu-hyperaccumulators. 35S lines showed enhanced Cu sensitivity. Second, <i>copC</i> was engineered under the control of the <i>cab1</i> (chlorophyll a/b binding protein 1) promoter, in order to drive <i>copC</i> expression to the shoots (transgenic lines cab1-copC). cab1-copC lines showed increased Cu translocation factors (twice that of wild-type plants) and also displayed enhanced Cu sensitivity. Finally, subcellular targeting the CopC protein to plant vacuoles was addressed by expressing a modified <i>copC</i> gene containing specific vacuole sorting determinants (transgenic lines 35S-copC-V). Unexpectedly, increased Cu-accumulation was not achievedneither in roots nor in shootswhen compared to 35S-copC lines. Conversely, 35S-copC-V lines did display greatly enhanced Cu-hypersensitivity. Our results demonstrate the feasibility of obtaining Cu-hyperaccumulators by engineering a prokaryotic Cu-binding protein, but they highlight the difficulty of altering the exquisite Cu homeostasis in plants

Biofertilization with PGP Bacteria Improve Strawberry Plant Performance under Sub-Optimum Phosphorus Fertilization

Biofertilization with plant growth-promoting bacteria (PGPB) could optimize chemical fertilization for strawberry crop cultivation. A greenhouse study was arranged to assess the impact of an isolated PGPB consortium from halophytes on strawberry development, physiological traits, and nutritional balance subjected to two phosphorus fertilization limitation treatments (with and without insoluble phosphorus form application). Biofertilization had a positive effect on strawberry development. Thus, shoot and root biomass was c. 20 and 32% higher in inoculated plants grown with insoluble phosphorus. This effect was mediated by a positive bacterial impact on plant carbon absorption capacity and water use efficiency, through a reduction in CO2 diffusional and biochemical photosynthesis limitation. Thus, net photosynthetic rate and intrinsic water use efficiency showed increments of 21–56% and 14–37%, respectively. In addition, inoculation led to a better efficiency of the plant photochemical apparatus, as indicated by the invariable higher PSII photochemistry parameters. Furthermore, these effects correlated with improved nutritional balance of phosphorus and nitrogen, which was directly related to the beneficial impact on carbon metabolism and, consequently, on strawberries’ growth. In conclusion, we can recommend the biofertilization based on PGPB for achieving more efficient strawberry P fertilization management practices, providing high efficiency in yields

Biofertilization with PGP Bacteria Improve Strawberry Plant Performance under Sub-Optimum Phosphorus Fertilization

Biofertilization with plant growth-promoting bacteria (PGPB) could optimize chemical fertilization for strawberry crop cultivation. A greenhouse study was arranged to assess the impact of an isolated PGPB consortium from halophytes on strawberry development, physiological traits, and nutritional balance subjected to two phosphorus fertilization limitation treatments (with and without insoluble phosphorus form application). Biofertilization had a positive effect on strawberry development. Thus, shoot and root biomass was c. 20 and 32% higher in inoculated plants grown with insoluble phosphorus. This effect was mediated by a positive bacterial impact on plant carbon absorption capacity and water use efficiency, through a reduction in CO2 diffusional and biochemical photosynthesis limitation. Thus, net photosynthetic rate and intrinsic water use efficiency showed increments of 21&ndash;56% and 14&ndash;37%, respectively. In addition, inoculation led to a better efficiency of the plant photochemical apparatus, as indicated by the invariable higher PSII photochemistry parameters. Furthermore, these effects correlated with improved nutritional balance of phosphorus and nitrogen, which was directly related to the beneficial impact on carbon metabolism and, consequently, on strawberries&rsquo; growth. In conclusion, we can recommend the biofertilization based on PGPB for achieving more efficient strawberry P fertilization management practices, providing high efficiency in yields

Consortia of Plant-Growth-Promoting Rhizobacteria Isolated from Halophytes Improve Response of Eight Crops to Soil Salinization and Climate Change Conditions

Soil salinization is an environmental problem that adversely affects plant growth and crop productivity worldwide. As an alternative to the conventional approach of breeding salt-tolerant plant cultivars, we explored the use of plant-growth-promoting rhizobacteria (PGPR) from halophytic plants to enhance crop growth under saline conditions. Here, we report the effect of five PGPR consortia from halophytes on the growth of eight (alfalfa, flax, maize, millet, rice, strawberry, sunflower, and wheat) of the crops most commonly produced on salinized soils worldwide. To test the efficiency of halotolerant consortia, we designed a complex environmental matrix simulating future climate-change scenarios, including increased CO2 levels and temperature. Overall, biofertilizers enhanced growth of most crops with respect to non-inoculated control plants under different CO2 concentrations (400/700 ppm), temperatures (25/+4 °C), and salinity conditions (0 and 85 mM NaCl). Biofertilizers counteracted the detrimental effect of salinity on crop growth. Specifically, strawberry and rice showed the greatest positive additive response to inoculation in the presence of salt; above-ground biomasses were 35% and 3% greater, respectively, than their respective control grown without salt. Furthermore, depending on the interaction of environmental factors (salinity × CO2 × temperature) analyzed, the results varied—influencing the most effective biofertilizer determined for each crop now, or in the future. Our findings highlight the importance of conducting studies that consider stress interaction for realistic assessments of the potential of biofertilizers in a climate-changed world