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Poly- and perfluoroalkyl substances (PFASs) are synthetic chemicals, which are introduced to the environment through anthropogenic activities. Aqueous film forming foam used in firefighting, wastewater effluent, landfill leachate, and biosolids are major sources of PFAS input to soil and groundwater. Remediation of PFAS contaminated solid and aqueous media is challenging, which is attributed to the chemical and thermal stability of PFAS and the complexity of PFAS mixtures. In this review, remediation of PFAS contaminated soils through manipulation of their bioavailability and destruction is presented. While the mobilizing amendments (e.g., surfactants) enhance the mobility and bioavailability of PFAS, the immobilizing amendments (e.g., activated carbon) decrease their bioavailability and mobility. Mobilizing amendments can be applied to facilitate the removal of PFAS though soil washing, phytoremediation, and complete destruction through thermal and chemical redox reactions. Immobilizing amendments are likely to reduce the transfer of PFAS to food chain through plant and biota (e.g., earthworm) uptake, and leaching to potable water sources. Future studies should focus on quantifying the potential leaching of the mobilized PFAS in the absence of removal by plant and biota uptake or soil washing, and regular monitoring of the long-term stability of the immobilized PFAS. © 2020 Elsevier B.V.

Isocitrate lyase is important for lipid utilisation by Mycobacterium tuberculosis but its ICL2 isoform is poorly understood. Here we report that binding of the lipid metabolites acetyl-CoA or propionyl-CoA to ICL2 induces a striking structural rearrangement, substantially increasing isocitrate lyase and methylisocitrate lyase activities. Thus, ICL2 plays a pivotal role regulating carbon flux between the tricarboxylic acid (TCA) cycle, glyoxylate shunt and methylcitrate cycle at high lipid concentrations, a mechanism essential for bacterial growth and virulence.

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The enzymes isocitrate lyase (ICL) isoforms 1 and 2 are essential for Mycobacterium tuberculosis survival within macrophages during latent tuberculosis (TB). As such, ICLs are attractive therapeutic targets for the treatment of tuberculosis. However, there are few biophysical assays that are available for accurate kinetic and inhibition studies of ICL in vitro. Herein we report the development of a combined NMR spectroscopy and thermal shift assay to study ICL inhibitors for both screening and inhibition constant (IC50) measurement. Operating this new assay in tandem with virtual high-throughput screening has led to the discovery of several new ICL1 inhibitors.

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen, capable of surviving in a broad range of natural environments and quickly acquiring resistance. It is associated with hospital-acquired infections, particularly in patients with compromised immunity, and is the primary cause of morbidity and mortality in cystic fibrosis (CF) patients. P. aeruginosa is also of nosocomial importance on dairy farms and veterinary hospitals, where it is a key morbidity factor in bovine mastitis. P. aeruginosa uses a cell-cell communication system consisting of signalling molecules to coordinate bacterial secondary metabolites, biofilm formation, and virulence. Simple and sensitive methods for the detection of biomolecules as indicators of P. aeruginosa infection would be of great clinical importance. Here, we report the synthesis of the P. aeruginosa natural product, barakacin, which was recently isolated from the bovine ruminal strain ZIO. A simple and sensitive electrochemical method was used for barakacin detection using a boron-doped diamond (BDD) and glassy carbon (GC) electrodes, based on cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The influence of electrolyte pH on the peak potential and peak currents was also investigated. At pH 2.0, the peak current was linearly dependent on barakacin concentration (in the range used, 1-10 µM), with correlation coefficients greater than 0.98 on both electrodes. The detection limit (S/N?=?3) on the BDD electrode was 100-fold lower than that obtained on the GC electrode. The optimized method using the BDD electrode was extended to bovine (cow feces) and human (sputum of a CF patient) samples. Spiked barakacin was easily detected in these matrices at a limit of 0.5 and 0.05 µM, respectively. Graphical abstract Electrochemical detection of barakacin.

We applied two process-based models in a hedgerow olive orchard with the aim of understanding the limitations and mechanisms behind the control of transpiration in olive trees under drip irrigation. One model is based on the biophysics of water flow through the porous media of soil and xylem. The other is a hydromechanical model based on the observed dependence of stomatal aperture on whole-plant and epidermis water relations. The experiments were made in a hedgerow olive orchard (1667 trees ha−1) planted with 5-year-old ‘Arbequina’ trees. Measurements were made in control trees irrigated to replace 100% of the crop water needs, and in trees under regulated deficit irrigation (RDI) strategy, in which irrigation replaced ca. 30% of the control. Soil physical properties, root distribution, leaf area, sap flow, leaf osmotic pressure and key variables of leaf gas exchange and water status were measured and models were applied. Results show how in our orchard, with a shallow root distribution and very coarse soil, most of the limitation to transpiration was imposed by the hydraulics of the rhizosphere. The model shows how this limitation was related to the ratio of root to leaf area, and how this ratio can be managed by canopy pruning or by changing the number of drippers. Likewise, osmotic adjustment occurred similarly in both irrigation treatments, despite differences found on leaf water potential. Water stress largely affected plant hydraulic conductivity of RDI trees. A potential involvement of regulating signals, other than purely hydraulics, was evident in both treatments, although our data suggests that these signals were not regulated by the soil water status only.

Xylem hydraulic conductivity (K) is typically defined as K = F/(P/L), where F is the flow rate through a xylem segment associated with an applied pressure gradient (P/L) along the segment. This definition assumes a linear flow–pressure relationship with a flow intercept (F0) of zero. While linearity is typically the case, there is often a non-zero F0 that persists in the absence of leaks or evaporation and is caused by passive uptake of water by the sample. In this study, we determined the consequences of failing to account for nonzero F0 for both K measurements and the use of K to estimate the vulnerability to xylem cavitation. We generated vulnerability curves for olive root samples (Olea europaea) by the centrifuge technique, measuring a maximally accurate reference Kref as the slope of a four-point F vs P/L relationship. The Kref was compared with three more rapid ways of estimating K. When F0 was assumed to be zero, K was significantly under-estimated (average of −81.4 ± 4.7%), especially when Kref was low. Vulnerability curves derived from these under-estimated K values overestimated the vulnerability to cavitation. When non-zero F0 was taken into account, whether it was measured or estimated, more accurate K values (relative to Kref) were obtained, and vulnerability curves indicated greater resistance to cavitation. We recommend accounting for non-zero F0 for obtaining accurate estimates of K and cavitation resistance in hydraulic studies.