Methane removal efficiencies of biochar-mediated landfill soil cover with reduced depth.

Biochar amendment for landfill soil cover has the potential to enhance methane removal efficiency while minimizing the soil depth. However, there is a lack of information on the response of biochar-mediated soil cover to the changes in configuration and operational parameters during the methane transport and transformation processes. This study constructed three biochar-amended landfill soil covers, with reduced soil depths from 75 cm (C2) to 55 cm (C3) and 45 cm (C4), and the control group (C1) with 75 cm and no biochar. Two operation phases were conducted under two soil moisture contents and three inlet methane fluxes in each phase. The methane removal efficiency increased for all columns along with the increase in methane flux. However, increasing moisture content from 10% to 20% negatively influenced the methane removal efficiency due to mass transfer limitation when at a low inlet methane flux, especially for C1; while this adverse effect could be alleviated by a high flux. Except for the condition with low moisture content and flux combination, C3 showed comparable methane removal efficiency to C2, both dominating over C1. As for C4 with only 45 cm, a high moisture content combined with a high methane flux enabled its methane removal efficiency to be competitive with other soil depths. In addition to the geotechnical reasons for gas transport processes, the evolution in methanotroph community structure (mainly type I methanotrophs) induced by biochar amendment and variations in soil properties supplemented the biological reasons for the varying methane removal efficiencies.

Manipulating soil microbial community assembly by the cooperation of exogenous bacteria and biochar for establishing an efficient and healthy CH4 biofiltration system.

Manipulating the methanotroph (MOB) composition and microbial diversity is a promising strategy to optimize the methane (CH4) biofiltration efficiency of an engineered landfill cover soil (LCS) system. Inoculating soil with exogenous MOB-rich bacteria and amending soil with biochar show strong manipulating potential, but how the two stimuli interactively shape the microbial community structure and diversity has not been clarified. Therefore, three types of soils with active CH4 activities, including paddy soil, river wetland soil, and LCS were selected for enriching MOB-dominated communities (abbreviated as B_PS, B_RWS, and B_LCS, respectively). They were then inoculated to LCS which was amended with two distinct biochar. Besides the aerobic CH4 oxidation efficiencies, the evolution of the three microbial communities during the MOB enrichment processes and their colonization in two-biochar amended LCS were obtained. During the MOB enriching, a lag phase in CH4 consumption was observed merely for B_LCS. Type II MOB Methylocystis was the primary MOB for both B_PS and B_LCS; while type I MOB dominated for B_RWS and the major species were altered by gas concentrations. Compared to biochar, a more critical role was demonstrated for the bacteria inoculation in determining the community diversity and function of LCS. Instead, biochar modified the community structures by mainly stimulating the dominant MOB but could induce stochastic processes in community assembly, possibly related to its inorganic nutrients. Particularly, combined with biochar advantages, the paddy soil-derived bacteria consortiums with diverse MOB species demonstrated the potent adaption to LCS niches, not only retaining the high CH4-oxidizing capacities but also shaping a community structure with more diverse soil function. The results provided new insights into the optimization of an engineered CH4-mitigation soil system by manipulating the soil microbiomes with the cooperation of exogenous bacteria and biochar.

Site-specific unnatural base excision via visible light.

Base excision (BE) is an important yet hard-to-control biological event. Unnatural base pairs are powerful tools to revolutionize biological studies in various areas. In this paper, we report a visible-light-induced method to construct site-specific unnatural BE and show the influence of its regulation on transcription and translation levels.

Transcription, Reverse Transcription, and Amplification of Backbone-Modified Nucleic Acids with Laboratory-Evolved Thermophilic DNA Polymerases.

Backbone-modified nucleic acids are usually more stable enzymatically than their natural counterparts, enabling their broad application as potential diagnostic or therapeutic agents. Moreover, the development of nucleic acids with unnatural backbones has expanded the pool of genetic information carriers and paved the way toward synthetic xenobiology. However, synthesizing these molecules remains very challenging due to the requirement for harsh reaction conditions and the low coupling efficiency during their traditional solid-phase synthesis. Although enzymatic synthesis provides an attractive alternative that also allows the replication and artificial evolution of these molecules, it is crucially dependent on the availability of polymerases capable of synthesizing these backbone-modified nucleotides. Previously, a series of thermostable polymerases that can efficiently synthesize or even amplify backbone-modified DNA or RNA have been evolved through a polymerase evolution method based on phage display. Herein we summarize protocols to use these evolved polymerase mutants to transcribe, reverse transcribe, and PCR amplify backbone-modified nucleic acids. We also outline the polymerase chain transcription method, developed later for the rapid production of RNA or backbone-modified RNA with one of these evolved polymerases, SFM4-3. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Transcription/synthesis of modified DNA/RNA from DNA templates with evolved polymerases SFM4-3 or SFM4-6 Basic Protocol 2: Reverse transcription of modified DNA/RNA with evolved polymerase SFM4-9 Basic Protocol 3: PCR amplification of modified DNA with evolved polymerase SFM4-3 Basic Protocol 4: Polymerase chain transcription for the production of RNA/modified RNA oligonucleotides with evolved polymerase SFM4-3.