Microbiomes are vast communities of microbes and viruses that populate all natural ecosystems. Viruses have been considered the most variable component of microbiomes, as supported by virome surveys and examples of high genomic mosaicism. However, recent evidence suggests that the human gut virome is remarkably stable compared to other environments. Here we investigate the origin, evolution, and epidemiology of crAssphage, a widespread human gut virus. Through a global collaboratory, we obtained DNA sequences of crAssphage from over one-third of the world's countries, and showed that its phylogeography is locally clustered within countries, cities, and individuals. We also found colinear crAssphage-like genomes in both Old-World and New-World primates, challenging genomic mosaicism and suggesting that the association of crAssphage with primates may be millions of years old. We conclude that crAssphage is a benign globetrotter virus that may have co-evolved with the human lineage and an integral part of the normal human gut virome.

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The synthesis of hydrogen peroxide (H2O2) from H2O and O2 by metal-free photocatalysts (e.g., graphitic carbon nitride, C3N4) is a potentially promising approach to generate H2O2. However, the photocatalytic H2O2 generation activity of the pristine C3N4 in pure H2O is poor due to unpropitious rapid charge recombination and unfavorable selectivity. Herein, we report a facile method to boost the photocatalytic H2O2 production by grafting cationic polyethylenimine (PEI) molecules onto C3N4. Experimental results and density functional theory (DFT) calculations demonstrate PEI can tune the local electronic environment of C3N4. The unique intermolecular electronic interaction in PEI/C3N4 not only improves the electron–hole separation but also promotes the two-electron O2 reduction to H2O2 via the sequential two-step single-electron reduction route. With the synergy of improved charge separation and high selectivity of two-electron O2 reduction, PEI/C3N4 exhibits an unexpectedly high H2O2 generation activity of 208.1 μmol g–1 h–1, which is 25-fold higher than that of pristine C3N4. This study establishes a paradigm of tuning the electronic property of C3N4 via functional molecules for boosted photocatalysis activity and selectivity.

Nanomaterials open an alternative way for water disinfection. However, limitations such as aggregation, toxicity, and complex post‐treatment block their practical application. In this study, an antibacterial silver/reduced graphene oxide (Ag/rGO) hydrogel consisting of controlled porous rGO network and well‐dispersed Ag nanoparticle is synthesized by a facile hydrothermal reaction. Scanning electron microscopy, transmission electron microscope, X‐ray diffraction, mercury porosimetry, and Fourier transform IR spectroscopy are employed to characterize the Ag/rGO hydrogel. The 3D structure of the rGO network serves as an excellent support for Ag nanoparticles. Disinfection experiments show that the Ag/rGO hydrogel exhibits good efficacy against Escherichia coli when used as a bactericidal filter driven by gravity. The mechanistic study indicates that bacteria cells are inactivated due to cell membrane damage induced by silver nanoparticles and rGO nanosheets when they flow through Ag/rGO hydrogel. Moreover, due to the retaining of Ag by rGO, the leaching level of silver from Ag/rGO hydrogel is considerably lower than the drinking water standard. This study sheds new light on designing antibacterial materials for point‐of‐use water disinfection application.

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The shedding of pathogens by infected humans enables the use of sewage monitoring to conduct wastewater-based epidemiology (WBE). Although most WBE studies use data from large sewage treatment plants, timely data from smaller catchments are needed for targeted public health action. Traditional sampling methods, like autosamplers or grab sampling, are not conducive to quick ad hoc deployments and high-resolution monitoring at these smaller scales. This study develops and validates a cheap and easily deployable passive sampler unit, made from readily available consumables, with relevance to the COVID-19 pandemic but with broader use for WBE. We provide the first evidence that passive samplers can be used to detect SARS-CoV-2 in wastewater from populations with low prevalence of active COVID-19 infections (0.034 to 0.34 per 10,000), demonstrating their ability for early detection of infections at three different scales (lot, suburb, and city). A side by side evaluation of passive samplers ( n = 245) and traditionally collected wastewater samples ( n = 183) verified that the passive samplers were sensitive at detecting SARS-CoV-2 in wastewater. On all 33 days where we directly compared traditional and passive sampling techniques, at least one passive sampler was positive when the average SARS-CoV-2 concentration in the wastewater equaled or exceeded the quantification limit of 1.8 gene copies per mL ( n = 7). Moreover, on 13 occasions where wastewater SARS-CoV-2 concentrations were less than 1.8 gene copies per mL, one or more passive samplers were positive. Finally, there was a statistically significant ( p < 0.001) positive relationship between the concentrations of SARS-CoV-2 in wastewater and the levels found on the passive samplers, indicating that with further evaluation, these devices could yield semi-quantitative results in the future. Passive samplers have the potential for wide use in WBE with attractive feasibility attributes of cost, ease of deployment at small-scale locations, and continuous sampling of the wastewater. Further research will focus on the optimization of laboratory methods including elution and extraction and continued parallel deployment and evaluations in a variety of settings to inform optimal use in wastewater surveillance.

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