Optically Mediated Hydrogel-Based Ionic Diode.

Ionic diodes with environmentally modulated ion-rectifying characteristics have attracted much attention and show great promise in the construction of smart devices with environmental adaptability. One immediate challenge is to integrate stimuli responsiveness and ion rectification into one single ionic diode, which requires a close cooperation of chemical principles and device technologies. Herein, an ionic diode based on a photoresponsive hydrogel with optically mediated ion-rectifying performances is introduced. Relying on the photoresponsive concentration of proton in the hydrogel, the ionic current rectification can be prominently enhanced upon ultraviolet (UV) irradiation. A maximum ionic current rectification ratio of the optically mediated ionic diode about 4 × 105 is achieved. Furthermore, the hydrogel-based diode can serve as an AND logic gate operated by UV light and voltage bias as two independent inputs. As a proof of concept, to use the optically mediated diode is achieved to modulate the feedback of a robot with logic behaviors. This work provides a novel and valuable strategy for designing functional hydrogel-based devices with the integration of stimuli-responsiveness and logic signal processing through chemical approaches.

1,520 reference genomes from cultivated human gut bacteria enable functional microbiome analyses.

Reference genomes are essential for metagenomic analyses and functional characterization of the human gut microbiota. We present the Culturable Genome Reference (CGR), a collection of 1,520 nonredundant, high-quality draft genomes generated from >6,000 bacteria cultivated from fecal samples of healthy humans. Of the 1,520 genomes, which were chosen to cover all major bacterial phyla and genera in the human gut, 264 are not represented in existing reference genome catalogs. We show that this increase in the number of reference bacterial genomes improves the rate of mapping metagenomic sequencing reads from 50% to >70%, enabling higher-resolution descriptions of the human gut microbiome. We use the CGR genomes to annotate functions of 338 bacterial species, showing the utility of this resource for functional studies. We also carry out a pan-genome analysis of 38 important human gut species, which reveals the diversity and specificity of functional enrichment between their core and dispensable genomes.