PDF(Pubmed)
Abstract：
Particulate carbon (C) degradation in soils is a critical process in the global C cycle governing greenhouse gas fluxes and C storage. Millimeter-scale soil aggregates impose strong controls on particulate C degradation by inducing chemical gradients of e.g. oxygen, as well as limiting microbial mobility in pore structures. To date, experimental models of soil aggregates have incorporated porosity and chemical gradients but not particulate C. Here, we demonstrate a proof-of-concept encapsulating microbial cells and particulate C substrates in hydrogel matrices as a novel experimental model for soil aggregates. Ruminiclostridium cellulolyticum was co-encapsulated with cellulose in millimeter-scale polyethyleneglycol-dimethacrylate (PEGDMA) hydrogel beads. Microbial activity was delayed in hydrogel-encapsulated conditions, with cellulose degradation and fermentation activity being observed after 13 days of incubation. Unexpectedly, hydrogel encapsulation shifted product formation of R. cellulolyticum from an ethanol-lactate-acetate mixture to an acetate-dominated product profile. Fluorescence microscopy enabled simultaneous visualization of the PEGDMA matrix, cellulose particles, and individual cells in the matrix, demonstrating growth on cellulose particles during incubation. Together, these microbe-cellulose-PEGDMA hydrogels present a novel, reproducible experimental soil surrogate to connect single cells to process outcomes at the scale of soil aggregates and ecosystems.
摘要：
土壤中的颗粒碳（C）降解是全球C循环中控制温室气体通量和C存储的关键过程。毫米尺度的土壤聚集体通过诱导例如氧气的化学梯度对颗粒碳降解施加强有力的控制。以及限制微生物在孔隙结构中的流动性。迄今为止,土壤团聚体的实验模型结合了孔隙度和化学梯度，但没有颗粒C。我们展示了将微生物细胞和颗粒C基质封装在水凝胶基质中的概念验证，作为土壤团聚体的新型实验模型。将Ruminiclostridium纤维素与纤维素共封装在毫米级聚乙二醇-二甲基丙烯酸酯（PEGDMA）水凝胶珠中。在水凝胶封装的条件下，微生物活性被延迟，培养13天后观察到纤维素降解和发酵活性。出乎意料的是,水凝胶封装将分解纤维素的产物形成从乙醇-乳酸酯-乙酸酯混合物转变为乙酸酯为主的产物谱。荧光显微镜使PEGDMA矩阵的同时可视化，纤维素颗粒，和矩阵中的单个细胞，证明在培养过程中纤维素颗粒的生长。一起,这些微生物-纤维素-PEGDMA水凝胶提出了一种新型的，可重复的实验土壤替代品，以连接单细胞以处理土壤团聚体和生态系统规模的结果。
