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Aims: Heavy metals are one of the most important pollutants in earth and water environments due to long-term durability. The aim of this study was to isolate phosphate solubilizing bacteria from metal waste, investigate the amount of resistance, remove the metal by it and the effect of phosphatase on removal of metals.
Materials & Methods: In this experimental study, the isolation of phosphate solubilizing bacteria and detection of isolates were carried out, using biochemical and molecular tests. The phosphatase was measured by colorimetric method, the resistance of the separated to the metals with the minimum inhibitory concentration (MIC₅₀), minimum bactericidal concentration (MBC) and the rate of removal of metals by atomic absorption was measured. The surface changes of the exposed metal cells were investigated by Fourier Transform Infrared Spectroscopy (FTIR) and the effect of phosphatase on metal removal. Data analysis was done with Duncan's test, using Excel 2013 and SPSS 20 software.
Findings: Serratia proteamaculans was identified as producer of the acid phosphatase. The highest MIC and MBC were obtained for Nickel (Ni) and Lead (Pb), respectively. The most metal removal was for Pb. MIC₅₀ of Chrome and Cadmium were obtained less than 0.1mM and 1mM, and their removal percentage by the isolate were 18% and 48%, respectively. According to the FTIR, 988.339cm^-1 wavelength was observed in the cells treated by 5mM Pb that is related to the Pb₃(PO₄)₂. The isolate showed the highest resistance and removal of Pb. The mechanism of Ni removal was associated to the cell surface, while Pb was removed by both of the cells and supernatant containing phosphatase.
Conclusion: Serratia proteamaculans is the phosphate solubilizing bacterium in metal waste. This bacterium produces an enzyme called phosphatase, which is a cause of lead removal.

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Application of oxygen releasing compounds (ORCs) is considered as a novel method in petroleum hydrocarbon remediation from groundwater. ORCs destroy chemically the contaminant by exposure to water which results in hydroxyl radical generation or biologically remove the pollution by biostimulation of the groundwater native microorganisms aerobically. In the present study, calcium peroxide (CaO₂) nanoparticles were applied to supply the required oxygen for growth and activity of the native microorganisms to consume naphthalene (20 ppm) as a carbon source. Additionally, the effect of CaO₂ content, temperature and pH on the performance of nanoparticles were investigated in the naphthalene removal. The results indicated that the microbial population was sharply increased in the presence of 400 mg/L of nanoparticles and at 30^oC and the contaminant was completely removed after 20 days at neutral pH. Furthermore, naphthalene was 100% remediated from groundwater at pH 3, 7.4 and 12 after 2, 20 and 30 days, respectively. This proved the acceleration of chemical oxidation under the acidic condition. At 15 and 30 ± 0.5 ^oC the contaminant was removed from the media within 15 and 20 days respectively. Meanwhile, only 75% of contaminant was remediated from groundwater within 30 days at 4 ±0.5^oC which was due to the reduction in the biological activity and the chemical reaction rate.

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The significance of mangrove species in the world is undeniable and planting artificial mangrove forests is a desirable solution to preserve mangroves. The mangroves provide us with superior ecological services and one of their main services is the bioremediation of heavy metals. Hence, this study aimed to assess the effects of artificial mangroves of Velayat Park of Bandar Abbas on the contamination, adsorption pattern and ecological risk of heavy metals in the sediment samples. Thirty samples were collected from two paralleled sampling sections included those without mangroves and containing mangroves. Each sampling area consisted of upper, middle and lower sections. After drying samples using an oven, the dried sediments were sieved by a 63-micrometer sieve and digested by nitric and hydrochloric acid mixture. The concentration of As, Cu, Fe, Ni, Pb, V, and Zn was determined using ICP. The studied factors suggested a high level of ecological risk for as and Pb and the highest risk was observed in the samples without mangroves and a lower risk was reported for samples containing mangroves. Comparing the results with sediment quality guidelines and other studies indicated a dangerous concentration of As. Pearson correlation coefficient values exhibited that artificial mangroves have significantly affected the adsorption pattern of heavy metals (p-Value < 0.05). The principal component analysis (PCA) showed that As and Pb are dominantly derived from oil products leakages and industrial sewages while Cu, Fe, Ni, V and Zn are predominantly derived from natural and geological sources.

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The present study was conducted to determine the plant growth-promoting activities of Bradyrhizobium sp. (vigna) strain MRM6 grown in the presence and absence of the selected herbicides, quizalafop-p-ethyl and clodinafop. The herbicide tolerant Bradyrhizobium sp. (vigna) strain MRM6 was further tested for bioremediation and plant growth promoting potential using greengram as a test crop, grown in soils treated with quizalafop-p-ethyl and clodinafop, at both recommended and higher dose rates. The quizalafop-p-ethyl and clodinafop tolerant Bradyrhizobium sp. (vigna) strain MRM6 recovered from the nodules of greengram plants produced a substantial amount of indole acetic acid, siderophores, hydrogen cyanide and ammonia, both in the presence and absence of technical grade quizalafop-p-ethyl and clodinafop under in vitro conditions. Both quizalafop-p-ethyl [40 (recommended dose), 80, and 120 µg kg-1 soil] and clodinafop [400 (recommended dose), 800, and 1200 µg kg-1 soil] decreased the growth of Bradyrhizobium sp. MRM6-inoculated and un-inoculated plants. Quizalafop-p-ethyl at all concentrations showed more phytotoxicity and affected the growth in terms of nodulation, total dry biomass, nutrients (nitrogen and phosphorus) uptake and seed yield compared to clodinafop or un-inoculated control. When the inoculant strain MRM6 was used with any concentration of the two herbicides, the growth and nodulation parameters of the plants were relatively better compared to the plants grown in soils treated solely (without inoculant) with the same concentration of each herbicide. For example, when strain MRM6 was used with 1200 µg clodinafop kg-1 soil, it increased the symbiotic attributes (nodule number, nodule dry mass, leghaemoglobin), whole biomass, root N, shoot N, root P, shoot P, seed yield, and grain protein by 14%, 62%, 60%, 102%, 23%, 31%, 9%, 10%, 72% and 4%, respectively, compared to the un-inoculated treatment having the same concentration of clodinafop. The present findings suggest that the bradyrhizobial strain MRM6 endowed with multiple properties could be used to facilitate the productivity of greengram under herbicide-stressed soils.

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 The objective of this study was to explore the microbial community diversities and the relationships between microbial community compositions and hydrochemical factors in nitrate contaminated groundwater of Hun River alluvial plain. The method of polymerase chain reaction (PCR)-denaturing, gradient gel electrophoresis (DGGE) gene fingerprints combined with canonical correspondence analysis（CCA） were applied. The Operational Taxonomic Units (OTUs) of all the sampling sites had a certain degree of heteroplasmy and 75% OTUs presented in less than half of the sampling sites. The un-weighted pair group mean average (UPGMA) cluster analysis showed that the microbial community similarity of all the sampling sites were not relatively high (0.6-0.8). The distribution of microbial community positively correlated with nitrate. The dominant bacteria of the nitrate contaminated groundwater mainly included Hyphomicrobium denitrifican sp., Halanaerobium praevalens sp., Desulfotomaculum reducens sp., Nitrosospira multiformis sp., among which the Nitrosospira multiformis sp.and Sulfurovum sp. existed in all the sampling sites. CCA results indicated that Mn²⁺and NO₃^- were the most relevant hydrochemical factors to regulate the microbial composition in nitrate contaminated groundwater of this area, and next were Fe²⁺ and SO₄^2- . The results could provide references for the bioremediation of the nitrate contaminated groundwater of Hun River alluvial plain