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3 recordsLinked to original sources
PubMed2026

Elevated water levels drive greenhouse gas mitigation in the riparian zone profile.

Wetlands are critical for climate regulation, with their hyporheic zone serving as sensitive interfaces for groundwater-soil-atmosphere exchange. These zones are active hotspots for carbon-nitrogen cycling and greenhouse gas (GHG) emissions (CO2, CH4, N2O), yet the impact of water level fluctuations on these emissions and their microbial drivers in freshwater wetlands remains poorly understood. This study investigated the spatiotemporal dynamics of GHG emissions and carbon-nitrogen coupling processes along riparian soil profiles of Baiyangdian Lake during water level fluctuations. Employing static chamber measurements, microcosms, quantitative PCR, Metagenome-Assembled genome (MAG) analyses, and Structural Equation Modeling (SEM), we observed that GHG emissions were significantly affected by water level fluctuations. Specifically, CO2 and N2O fluxes, as well as CO2 production potential were significantly lower at high-water-level conditions. Water level also emerged as a key driver of microbial community structure, with Methylococcaceae and Methanosarcinaceae as key regulators of CH4 emission, and Anaeromyxobacteraceae as central to N2O dynamics. A high-quality Methylomirabilales-like MAG, possessing the complete pathway for coupled nitrate reduction and methane oxidation, was identified. Its abundance negatively correlated with water level, suggesting that these C-N coupling bacteria contribute to reducing GHG emissions. This study provides crucial theoretical insights and identifies microbial targets for mitigating wetland GHG emission through hydrological management.

Greenhouse Gases↗
PubMed2026

Rewiring Carbon Metabolism in Bacillus methanolicus via Heterologous Phosphoketolase Expression Enhances Biomass Yield From Methanol and Reduces CO2 Loss.

Methylotrophic microbes are attractive alternatives to traditional heterotrophic production platforms, yet their efficiency is constrained by carbon loss through pyruvate decarboxylation and the oxidative branch of the RuMP cycle. The phosphoketolase (PKT) pathway provides a carbon-conserving alternative by cleaving fructose-6-phosphate and/or xylulose-5-phosphate into acetyl-phosphate, which can subsequently be converted to acetyl-coA without pyruvate decarboxylation. The remaining carbon intermediates are recycled through central metabolism to regenerate RuMP cycle intermediates without direct CO2 release. Here, we engineered this strategy in Bacillus methanolicus, a thermophilic methylotroph with strong industrial potential. We first established a versatile expression toolkit comprising inducible and constitutive promoters, benchmarked using an sfGFP reporter. Leveraging this system, we heterologously expressed the phosphoketolase B (pktB) gene from Methylotuvimicrobium buryatense 5GB1C which increased methanol-to-biomass yields by 18%-24% relative to controls and reduced biogenic CO2 production by 9%-12%. Chromosomal integration of pktB preserved these gains, demonstrating stability without reliance on plasmid-based expression. Together, these results show that PKT-driven metabolic rewiring enhances substrate yields in B. methanolicus and provides a scalable strategy to improve methylotrophic bioprocesses. This work expands the metabolic engineering toolbox for methylotrophs and highlights carbon-conserving pathway design as a key lever for advancing single carbon (C1) biomanufacturing.

Bacillus↗
PubMed2025

MmoD and MmoG Are Crucial for the Synthesis of Soluble Methane Monooxygenase in Methanotrophs.

Soluble methane monooxygenase (sMMO) from methanotrophs has been extensively investigated for decades. However, major knowledge gaps persist regarding the synthesis mechanism of sMMO, particularly concerning the ambiguous roles of mmoD and mmoG in the sMMO gene cluster. Here, the functions of mmoD and mmoG were investigated in a model methanotrophic strain, Methylotuvimicrobium buryatense 5GB1C. Both genes were found to be essential for the functional expression of sMMO. Genetic and biochemical data supported the hypothesis that MmoG acts as a folding chaperone for both MmoX and MmoR, while MmoD serves as an assembly chaperone for the hydroxylase component. The functional expression of sMMO in Escherichia coli was achieved in an mmoD- and mmoG-dependent manner. In addition, deletion of mmoD dramatically reduced the transcription of the sMMO cluster in M. buryatense 5GB1C, implying that MmoD may regulate the sMMO cluster via an unknown mechanism. Knockout of neither mmoD nor mmoG abolished the essential feature of "copper switch", indicating that they do not serve as the initial regulators of "copper switch". These results demonstrate the crucial roles of mmoD and mmoG in sMMO synthesis and offer new insights into heterologous expression of sMMO.

Oxygenases↗