BDDE-Inspired Chalcone Derivatives to Fight Bacterial and Fungal Infections

The growing number of infectious diseases around the world threatens the effective response of antibiotics, contributing to the increase in antibiotic resistance seen as a global health problem. Currently, one of the main challenges in antimicrobial drug discovery is the search for new compounds that not only exhibit antimicrobial activity, but can also potentiate the antimicrobial activity and revert antibiotics’ resistance, through the interference with several mechanisms, including the inhibition of efflux pumps (EPs) and biofilm formation. Inspired by macroalgae brominated bromophenol BDDE with antimicrobial activity, a series of 18 chalcone derivatives, including seven chalcones (9–15), six dihydrochalcones (16–18, and 22–24) and five diarylpropanes (19–21, and 25 and 26), was prepared and evaluated for its antimicrobial activity and potential to fight antibiotic resistance. Among them, chalcones 13 and 14 showed promising antifungal activity against the dermatophyte clinical strain of Trichophyton rubrum, and all compounds reversed the resistance to vancomycin in Enterococcus faecalis B3/101, with 9, 14, and 24 able to cause a four-fold decrease in the MIC of vancomycin against this strain. Compounds 17–24 displayed inhibition of EPs and the formation of biofilm by S. aureus 272123, suggesting that these compounds are inhibiting the EPs responsible for the extrusion of molecules involved in biofilm-related mechanisms. Interestingly, compounds 17–24 did not show cytotoxicity in mouse embryonic fibroblast cell lines (NIH/3T3). Overall, the results obtained suggest the potential of dihydrochalcones 16–18 and 22–24, and diarylpropanes 19–21, 25 and 26, as hits for bacterial EPs inhibition, as they are effective in the inhibition of EPs, but present other features that are important in this matter, such as the lack of antibacterial activity and cytotoxicity.     

Fish reproductive activity reveals temporal variations predominating spatial heterogeneity in maintaining high functional diversity of a Neotropical reservoir

The reproductive activity of the fish assemblage in a large Neotropical reservoir was evaluated by surveying the occurrence of ichthyoplankton in response to spatial and temporal variation in environmental factors. Fish reproduction was investigated by capturing larvae along representative spatial gradients in the main body (longitudinal) and arms (lateral) of the reservoir. After identification, the captured larvae were classified into different groups according to the functional traits of their parental stock. Sampling occurred monthly at night from October to March over five reproductive periods between 2009 and 2016, using conical-cylindrical plankton nets with flowmeter. Water samples were taken simultaneously allowing the measurement of environmental factors related to reproductive activity. The relationship between the environmental factors and the functional traits was assessed using RLQ and fourth-corner analyses. An evaluation of 51,995 larvae revealed there was greater larval abundance in the lacustrine and transition zones of both longitudinal and lateral gradients. Occurrences often correlated with temporal instead of spatial gradients. Higher rainfall correlated with abundances of detritivorous and migratory species. Higher water levels correlated with higher abundances of non-native species, species without parental care, with external fecundation, and partial spawning. Dry periods, with lower water and higher dissolved oxygen, correlated with higher abundances of insectivores and sedentary species. Although the presence of a dam-free stretch of river upstream of the reservoir had a positive influence on fish larvae in the fluvial zone, the results did not show differentiation along either gradient. Thus, the composition of the functional groups of fish species that reproduce in the Itaipu Reservoir appears to be predominantly influenced by the temporal variation in environmental factors rather than the formation of spatial gradients.     

Soil legacy phosphorus after 10 years of annual dairy liquid manure application in a no-tillage system

The benefits of manure as a source of nutrients for plants and to improve soil quality are well-known. Monitoring of manure application is needed if environmental issues are to be prevented. In particular, the availability and accumulation of phosphorus (P) has to be subject to rigorous monitoring. This study aims to both evaluate the efficacy of the resin method in extracting inorganic labile P in soils under the long-term application of dairy liquid manure (DLM), and verify the influence of DLM on the recovery of applied P and soil legacy P. To realize our objectives, two long-term field experiments were established under a no-tillage system with annual DLM application on sandy clay loam (sandy Oxisol) and clayey (clayey Oxisol) soils. Treatment consisted of DLM applications (0, 60, 120, 180 m³ ha⁻¹ year⁻¹), independent of mineral fertilizer. Soil samples were taken from the 0–5, 5–10 and 10–15 cm layers after 10 years from the beginning of the trial. A single extraction with resin underestimated inorganic labile P; however, successive extractions were able to take up 43% and 26% of the total P in sandy and clayey Oxisols, respectively, whereas in a single extraction the take-up was 17% and 8% from the same soils, respectively. The resin method was more effective in extracting P from the sandy Oxisol. Thus, when interpreting soil P contents for fertilizer planning, the soil texture should be taken into account. DLM application decreased P recovered from applied P, ranging from 54% to 83% (sandy), and 43% to 67% (clayey), and substantially increased soil legacy P.