Metaproteomic and gene expression analysis of interspecies interactions in a PAH-degrading synthetic microbial consortium constructed with the key microbes of a natural consortium.

Polycyclic Aromatic Hydrocarbons (PAHs) impose adverse effects on the environment and human life. The use of synthetic microbial consortia is promising in bioremediation of contaminated sites with these pollutants. However, the design of consortia taking advantage of natural interactions has been poorly explored. In this study, a dual synthetic bacterial consortium (DSC_AB) was constructed with two key members (Sphingobium sp. AM and Burkholderia sp. Bk), of a natural PAH degrading consortium. DSC_AB showed significantly enhanced degradation of PAHs and toxic intermediary metabolites relative to the axenic cultures, indicating the existence of synergistic relationships. Metaproteomic and gene-expression analyses were applied to obtain a view of bacterial performance during phenanthrene removal. Overexpression of the Bk genes, naph, biph, tol and sal and the AM gene, ahdB, in DSC_AB relative to axenic cultures, demonstrated that both strains are actively participating in degradation, which gave evidence of cross-feeding. Several proteins related to stress response were under-expressed in DSC_AB relative to axenic cultures, indicating that the division of labour reduces cellular stress, increasing the efficiency of degradation. This is the one of the first works revealing bacterial relationships during PAH removal in a synthetic consortium applying an omics approach. Our findings could be used to develop criteria for evaluating the potential effectiveness of synthetic bacterial consortia in bioremediation.

Oxidation of sulfonamides by ferrate(VI): Reaction kinetics, transformation byproducts and toxicity assesment.

This study was aimed at the degradation of sulfonamides (SNs) via oxidation with Fe(VI). The reaction kinetics, identification of degradation byproducts and their toxicity were investigated. The pH solution and Fe(VI) loading had significant effects on the degradation of the sulfonamides. The maximum degradation rate occurred at pH 3.0 with a 6:1 ratio Fe(VI): sulfonamide, obtaining 100% degradation of 15 mg L-1 SN within 5 min. Although Fe(VI) also showed an appreciable reactivity towards SNs (kapp = 9.85-19.63 × 102 M-1 s-1) at pH 7. The influence of solution pH on the values of kapp can be explained considering the specific reaction between Fe(VI) and SNs. Degradation rates are also influenced by the presence of inorganic ions in different water matrixes. For this reason, ions present in groundwater enhanced the SNs degradation through a synergistic effect among carbonates, sulfates and Fe(VI). Degradation byproducts identified, through UPLC analysis, allowed us to proposed three degradation pathways depending on pH. At acid pH there is a cleavage of C-S and S-N bonds. At neutral pH nitroso and nitro-derivates are formed. At basic pH hydroxylation is the main reaction. The cytotoxicity assay of HEK-293 and J774 cell lines exposed to Fe(VI) indicated that transformation byproducts had a lower toxicity than SNs as baseline products. Accordingly, this research suggests that Fe(VI) can act as a chemical oxidant to remove SNs antibiotics and it can be used to treat antibiotic pollution in wastewater.

Degradation of glyphosate in a Colombian soil is influenced by temperature, total organic carbon content and pH.

Glyphosate is one of the most used herbicides in the world. The fate of glyphosate in tropical soils may be different from that in soils from temperate regions. In particular, the amounts and types of non-extractable residues (NER) may differ considerably, resulting in different relative contributions of xenoNER (sorbed and sequestered parent compound) and bioNER (biomass residues of degraders). In addition, environmental conditions and agricultural practices leading to total organic carbon (TOC) or pH variation can alter the degradation of glyphosate. The aim of this study is thus to investigate how the glyphosate degradation and turnover are influenced by varying temperature, pH and TOC of sandy loam soil from Colombia. The pH or TOC of a Colombian soil was modified to yield five treatments: control (pH 7.0, TOC 3%), 4% TOC, 5% TOC, pH 6.5, and pH 5.5. Each treatment received 50 mg kg-1 of 13C315N-glyphosate and was incubated at 10 °C, 20 °C and 30 °C for 40 days. Rising temperature increased the mineralization of 13C315N-glyphosate from 13 to 20% (10 °C) to 32-39% (20 °C) and 41-51% (30 °C) and decreased the amounts of extractable 13C315N-glyphosate after 40 days of incubation from 13 to 26% (10 °C) to 4.6-12% (20 °C) and 1.2-3.2% (30 °C). Extractable 13C315N-glyphosate increased with higher TOC and higher pH. Total 13C-NER were similar in all treatments and at all temperatures (47%-60%), indicating that none of the factors studied affected the amount of total 13C-NER. However, 13C-bioNER dominated within the 13C-NER pool in the control and the 4% TOC treatment (76-88% of total 13C-NER at 20 °C and 30 °C), whereas in soil with 5% TOC and pH 6.5 or 5.5 13C-bioNER were lower (47-61% at 20 °C and 30 °C). In contrast, the 15N-bioNER pool was small (between 14 and 39% of the 15N-NER). Thus, more than 60% of 15N-NER is potentially hazardous xenobiotic NER which need careful attention in the future.

Isolation and characterization of a promoter responsive to salt, osmotic and dehydration stresses in soybean

Abstract Drought stress is the main limiting factor of soybean yield. Currently, genetic engineering has been one important tool in the development of drought-tolerant cultivars. A widely used strategy is the fusion of genes that confer tolerance under the control of the CaMV35S constitutive promoter; however, stress-responsive promoters would constitute the best alternative to the generation of drought-tolerant crops. We characterized the promoter of α-galactosidase soybean (GlymaGAL) gene that was previously identified as highly up-regulated by drought stress. The β-glucuronidase (GUS) activity of Arabidopsis transgenic plants bearing 1000- and 2000-bp fragments of the GlymaGAL promoter fused to the uidA gene was evaluated under air-dried, polyethylene glycol (PEG) and salt stress treatments. After 24 h of air-dried and PEG treatments, the pGAL-2kb led to an increase in GUS expression in leaf and root samples when compared to the control samples. These results were corroborated by qPCR expression analysis of the uidA gene. The pGAL-1kb showed no difference in GUS activity between control and treated samples. The pGAL-2kb promoter was evaluated in transgenic soybean roots, leading to an increase in EGFP expression under air-dried treatment. Our data indicates that pGAL-2kb could be a useful tool in developing drought-tolerant cultivars by driving gene expression.

Electrochemical degradation of the dimethyl phthalate ester on a fluoride-doped Ti/ß-PbO2 anode.

The electrooxidation of the dimethyl phthalate (DMP) ester was galvanostatically carried out in a filter-press reactor using a fluoride-doped lead dioxide (ß-PbO2,F) film electrodeposited on a Ti substrate. The variables investigated were the nature of the supporting electrolyte (NaCl and Na2SO4), pH (3, 7, and 10), current density (10, 20, 40, 60, and 80mAcm(-2)), and temperature (10, 20, 30, 40, and 50°C). The removal of DMP was monitored through high performance liquid chromatography (HPLC) and total organic carbon (TOC) analysis. The best conditions were obtained using Na2SO4 and at low current densities, independent of the solution pH or temperature. These conditions led to the highest levels of current efficiencies and complete combustion. However, the TOC removal levels were low, due to the generation of highly oxidized intermediates, which was confirmed by the intermediates detected by HPLC.

Aerobic biodegradation of nonylphenol ethoxylates in shaking-flask test

Nonylphenol ethoxylates (NPEOs), which are widely used for industrial and domestic purposes, exert adverse effects on wildlife after being used and discharged into the environment. However, their ultimate biodegradability and biodegradation pathway remains unclear. In this study, the aerobic degradability of nonylphenol ethoxylates (NPEOs) by the acclimated microorganisms in active sludge was examined using shaking-flask tests. The degradation of benzene rings in NPEOs was determined using UV spectroscopy and high performance liquid chromatography (HPLC). Results showed that more than 80 percent of benzene rings were removed after 8-10 days of degradation, and the majority of NPEOs were also removed after 9 days of degradation, indicating NPEOs and the benzene rings could be ultimately degraded by microorganisms in acclimated active sludge. Electrospray ionization-mass spectroscopy (ESI-MS) analysis of biodegradation intermediates indicate that stepwise omega, beta-oxidation of EO chains or fission of EO chains, and further omega, beta-oxidation of alkyl-chain for short-EO-chain NPEOs constitute the main pathway in the early stage, and complete biodegradation occur when the benzene rings in these molecules are opened in the later stage.