Bioengineering of non-pathogenic Escherichia coli to enrich for accumulation of environmental copper.

Heavy metal sequestration from industrial wastes and agricultural soils is a long-standing challenge. This is more critical for copper since copper pollution is hazardous both for the environment and for human health. In this study, we applied an integrated approach of Darwin's theory of natural selection with bacterial genetic engineering to generate a biological system with an application for the accumulation of Cu2+ ions. A library of recombinant non-pathogenic Escherichia coli strains was engineered to express seven potential Cu2+ binding peptides encoded by a 'synthetic degenerate' DNA motif and fused to Maltose Binding Protein (MBP). Most of these peptide-MBP chimeras conferred tolerance to high concentrations of copper sulphate, and in certain cases in the order of 160-fold higher than the recognised EC50 toxic levels of copper in soils. UV-Vis spectroscopic analysis indicated a molar ratio of peptide-copper complexes, while a combination of bioinformatics-based structure modelling, Cu2+ ion docking, and MD simulations of peptide-MBP chimeras corroborated the extent of Cu2+ binding among the peptides. Further, in silico analysis predicted the peptides possessed binding affinity toward a broad range of divalent metal ions. Thus, we report on an efficient, cost-effective, and environment-friendly prototype biological system that is potentially capable of copper bioaccumulation, and which could easily be adapted for the removal of other hazardous heavy metals or the bio-mining of rare metals.

An assessment of serum-dependent impacts on intracellular accumulation and genomic response of per- and polyfluoroalkyl substances in a placental trophoblast model.

Per- and polyfluoroalkyl substances (PFAS), a class of environmental contaminants, have been detected in human placenta and cord blood. The mechanisms driving PFAS-induced effects on the placenta and adverse pregnancy outcomes are not well understood. This study investigated the impact of perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and a replacement PFAS known as hexafluoropropylene oxide dimer acid (HFPO-DA, tradename GenX) on placental trophoblasts in vitro. Several key factors were addressed. First, PFAS levels in cell culture reagents at baseline were quantified. Second, the role of supplemental media serum in intracellular accumulation of PFAS in a human trophoblast (JEG3) cell line was established. Finally, the impact of PFAS on the expression of 96 genes involved in proper placental function in JEG3 cells was evaluated. The results revealed that serum-free media (SFM) contained no detectable PFAS. In contrast, fetal bovine serum-supplemented media (SSM) contained PFNA, PFUdA, PFTrDA, and 6:2 FTS, but these PFAS were not detected internally in cells. Intracellular accumulation following 24 hr treatments was significantly higher when cultured in SFM compared to SSM for PFOS and PFOA, but not HFPO-DA. Treatment with PFAS was associated with gene expression changes (n = 32) in pathways vital to placental function, including viability, syncytialization, inflammation, transport, and invasion/mesenchymal transition. Among the most robust PFAS-associated changes were those observed in the known apoptosis-related genes, BAD and BAX. These results suggest a complex relationship between PFAS, in vitro culture conditions, and altered expression of key genes necessary for proper placentation.

Investigating the effects of a sub-lethal metal mixture of Cu, Zn and Cd on bioaccumulation and ionoregulation in common carp, Cyprinus carpio.

The aquatic environment is continuously under threat because it is the final receptor and sink of waste streams. The development of industry, mining activities and agriculture gave rise to an increase in metal pollution in the aquatic system. Thus a wide occurrence of metal mixtures exists in the aquatic environment. The assessment of mixture stress remains a challenge considering that we can not predict the toxicity of a mixture on the basis of single compounds. Therefore the analysis of the effects of environmentally relevant waterborne mixtures is needed to improve our understanding of the impact of metal pollution in aquatic ecosystems. Our aim was to assess whether 10 % of the concentration of the 96 h LC50 (the concentration that is lethal to 50 % of the population in 96 h) of individual metal exposures can be considered as a "safe" concentration when applied in a trinomial mixture. Therefore, common carp were exposed to a sublethal mixture of Cu 0.07 ±â€¯0.001 µM (4.3 ±â€¯0.6 µg/L), Zn 2.71 ±â€¯0.81 µM (176.9 ±â€¯52.8 µg/L) and Cd 0.03 ±â€¯0.0004 µM (3.0 ±â€¯0.4 µg/L) at 20 °C for a period of one week. Parameters assessed included survival rate, bioaccumulation and physiological biomarkers related to ionoregulation and defensive mechanisms such as MT induction. Our results showed a sharp increase in Cu and Cd concentration in gills within the first day of exposure while Zn levels remained stable. The accumulation of these metals led to a Na drop in gills, liver and muscle as well as a decreased K content in the liver. Biomarkers related to Na uptake were also affected: on the first day gene expression for H+-ATPase was transiently increased while a concomitant decreased gene expression of the Na+/H+ exchanger occurred. A fivefold induction of metallothionein gene expression was reported during the entire duration of the experiment. Despite the adverse effects on ionoregulation all fish survived, indicating that common carp are able to cope with these low metal concentrations, at least during a one week exposure.