Alloying Pt electrocatalysts with late transition metals (e.g., Ni, Co, and Fe) is an effective strategy to lower the catalyst cost and improve their tolerance toward CO in the anode of direct ethanol fuel cells. In this study, shape-controlled octahedral Pt–Ni/C nanocrystals with uniformly exposed (111) facets and an average edge length of 10 nm were synthesized. The octahedral Pt–Ni/C nanocatalyst was at least 4.6 and 7.7 times more active than conventional Pt–Ni/C and commercial Pt/C catalysts, respectively. In situ infrared spectroscopic results showed that the acetic acid/CO2 absorbance peak intensity on octahedral Pt–Ni/C was 7.6 and 1.4 times higher as compared to commercial Pt/C and conventional Pt–Ni/C, respectively, at 0.75 V. This result suggests that ethanol oxidation on octahedral Pt–Ni produces more acetic acid than on other surfaces. The synergistic electronic and facet effects may explain the superior ethanol oxidation reaction activity of octahedral Pt–Ni/C. Further surface modification with Ru significantly lowered the onset potential for CO2 production by ∼100 mV and resulted in a higher selectivity on CO2 as compared to unmodified surface, which further boosted the ethanol utilization efficiency.
Recent laboratory evolution studies have shown that upon repetitive antibiotic treatments, bacterial populations will adapt and eventually became tolerant and resistant to the drug. Drug tolerance rapidly evolves upon frequent, intermittent antibiotic treatments, and such emerging drug tolerance seems to be specific to the treatment conditions, complicating clinical practice. Moreover, it has been shown that tolerance often promotes the development of resistance, which further reinforces the need of clinical diagnostics for antibiotic tolerance to reduce the occurrence of acquired resistance. Here, we discuss the laboratory evolution studies that were performed to track the development of tolerance in bacterial populations, and highlight the urgency of developing a comprehensive knowledge base of various tolerance phenotypes and their detection in clinics. Finally, we propose future directions for basic research in this growing field.
Persisters are a subpopulation of cells that have enhanced abilities to survive antibiotics and other stressful conditions. Recently, it was found that when persisters were repeatedly regrown and retreated with the same antibiotic for several cycles, the new population will become tolerant to the drug. In this study, we applied such cyclic antibiotic treatment on Escherichia coli populations using different classes of antibiotics (ampicillin, ciprofloxacin, and apramycin) during the exponential phase. After a few cycles, we observed that the evolved populations exhibit high tolerance to the specific class of antibiotic used during the evolution experiments, which are achieved by single-point mutations in one or several genes. Interestingly, all evolved populations show multidrug tolerance at the stationary phase, indicating that they have higher triggered persister fraction. Proteomic analysis and crosscomparison of the regulated proteomes of the tolerant populations during the stationary phase identified protein candidates with similar expression profiles that might be important for the tolerance phenotype. Susceptibility tests of mutants lacking gene coding for these protein candidates showed that they have significantly reduced survival toward antibiotics not only during the stationary phase, but also during the exponential phase. We demonstrated how proteomics, combined with cyclic antibiotic treatment as a means to enrich tolerant populations, is a promising avenue to obtain fresh insights into the phenomenon of persistence.
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