Assessing the Resolution of Methyltransferase-Mediated DNA Optical Mapping

[Image: see text] Interest in the human microbiome is growing and has been, for the past decade, leading to new insights into disease etiology and general human biology. Stimulated by these advances and in a parallel trend, new DNA sequencing platforms have been developed, radically expanding the possibilities in microbiome research. While DNA sequencing plays a pivotal role in this field, there are some technological hurdles that are yet to be overcome. Targeting of the 16S rRNA gene with amplicon sequencing, for instance, is frequently used for sample composition profiling due to its short sample-to-result time and low cost, which counterbalance its low resolution (genus to species level). On the other hand, more comprehensive methods, namely, whole-genome sequencing (WGS) and shallow shotgun sequencing, are capable of yielding single-gene- and functional-level resolution at a higher cost and much higher sample processing time. It goes without saying that the existing gap between these two types of approaches still calls for the development of a fast, robust, and low-cost analytical platform. In search of the latter, we investigated the taxonomic resolution of methyltransferase-mediated DNA optical mapping and found that strain-level identification can be achieved with both global and whole-genome analyses as well as using a unique identifier (UI) database. In addition, we demonstrated that UI selection in DNA optical mapping, unlike variable region selection in 16S amplicon sequencing, is not limited to any genomic location, explaining the increase in resolution. This latter aspect was highlighted by SCCmec typing in methicillin-resistant Staphylococcus aureus (MRSA) using a simulated data set. In conclusion, we propose DNA optical mapping as a method that has the potential to be highly complementary to current sequencing platforms

Tuning the Linkers in Polymer-Based Cathodes to Realize High Sulfur Content and High-Performance Potassium–Sulfur Batteries

The development of effective rechargeable potassium–sulfur (K–S) batteries has been retarded by a severe polysulfide shuttle effect and low sulfur content in the cathode (generally less than 40 wt %). Herein, a series of sulfur-linked polymers with different numbers of allyloxy linkers have been chosen to explore their effect on the performance of K–S batteries. By taking sulfur-linked tetra(allyloxy)-1,4-benzoquinone polymer (poly(S4-TABQ)) as the cathode of K–S batteries, its maximal sulfur content reaches ∼71 wt %, which displays a high capacity retention of 94.5% after 200 cycles (only 0.027% loss per cycle). Theoretical analyses and density functional theory calculations show that the abundant allyloxy linkers in poly(S4-TABQ) cathodes play a vital role in inhibiting the polysulfide shuttle effect and realizing high capacity, owing to the strong interaction of the allyloxy moieties with potassium polysulfides and the accelerated charge transfer during charge/discharge process. Moreover, ex situ X-ray photoelectron spectroscopy and ultraviolet–visible spectroscopy analysis are conducted to explore the electrochemical mechanism in poly(S4-TABQ) cathodes, indicating that −C-Sn–·K+ (n = 2–6) and K2Sn (n = 2–6) coexist in K–S batteries without the formation of K2S groups. This study provides a novel insight into the application of sulfur-linked polymers as cathode material in potassium–sulfur batteries