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  1. Abstract Developing an eco-friendly, efficient, and highly selective gold-recovery technology is urgently needed in order to maintain sustainable environments and improve the utilization of resources. Here we report an additive-induced gold recovery paradigm based on precisely controlling the reciprocal transformation and instantaneous assembly of the second-sphere coordinated adducts formed between β-cyclodextrin and tetrabromoaurate anions. The additives initiate a rapid assembly process by co-occupying the binding cavity of β-cyclodextrin along with the tetrabromoaurate anions, leading to the formation of supramolecular polymers that precipitate from aqueous solutions as cocrystals. The efficiency of gold recovery reaches 99.8% when dibutyl carbitol is deployed as the additive. This cocrystallization is highly selective for square-planar tetrabromoaurate anions. In a laboratory-scale gold-recovery protocol, over 94% of gold in electronic waste was recovered at gold concentrations as low as 9.3 ppm. This simple protocol constitutes a promising paradigm for the sustainable recovery of gold, featuring reduced energy consumption, low cost inputs, and the avoidance of environmental pollution.
    Free, publicly-accessible full text available December 1, 2024
  2. Free, publicly-accessible full text available December 21, 2023
  3. Abstract

    Although the phylumChloroflexotais ubiquitous, its biology and evolution are poorly understood due to limited cultivability. Here, we isolated two motile, thermophilic bacteria from hot spring sediments belonging to the genusTepidiformaand classDehalococcoidiawithin the phylumChloroflexota. A combination of cryo-electron tomography, exometabolomics, and cultivation experiments using stable isotopes of carbon revealed three unusual traits: flagellar motility, a peptidoglycan-containing cell envelope, and heterotrophic activity on aromatics and plant-associated compounds. Outside of this genus, flagellar motility has not been observed inChloroflexota, and peptidoglycan-containing cell envelopes have not been described inDehalococcoidia. Although these traits are unusual among cultivatedChloroflexotaandDehalococcoidia, ancestral character state reconstructions showed flagellar motility and peptidoglycan-containing cell envelopes were ancestral within theDehalococcoidia, and subsequently lost prior to a major adaptive radiation ofDehalococcoidiainto marine environments. However, despite the predominantly vertical evolutionary histories of flagellar motility and peptidoglycan biosynthesis, the evolution of enzymes for degradation of aromatics and plant-associated compounds was predominantly horizontal and complex. Together, the presence of these unusual traits inDehalococcoidiaand their evolutionary histories raise new questions about the timing and selective forces driving their successful niche expansion into global oceans.