Segregation of the Anodic Microbial Communities in a Microbial Fuel Cell Cascade.

Metabolic interactions within microbial communities are essential for the efficient degradation of complex organic compounds, and underpin natural phenomena driven by microorganisms, such as the recycling of carbon-, nitrogen-, and sulfur-containing molecules. These metabolic interactions ultimately determine the function, activity and stability of the community, and therefore their understanding would be essential to steer processes where microbial communities are involved. This is exploited in the design of microbial fuel cells (MFCs), bioelectrochemical devices that convert the chemical energy present in substrates into electrical energy through the metabolic activity of microorganisms, either single species or communities. In this work, we analyzed the evolution of the microbial community structure in a cascade of MFCs inoculated with an anaerobic microbial community and continuously fed with a complex medium. The analysis of the composition of the anodic communities revealed the establishment of different communities in the anodes of the hydraulically connected MFCs, with a decrease in the abundance of fermentative taxa and a concurrent increase in respiratory taxa along the cascade. The analysis of the metabolites in the anodic suspension showed a metabolic shift between the first and last MFC, confirming the segregation of the anodic communities. Those results suggest a metabolic interaction mechanism between the predominant fermentative bacteria at the first stages of the cascade and the anaerobic respiratory electrogenic population in the latter stages, which is reflected in the observed increase in power output. We show that our experimental system represents an ideal platform for optimization of processes where the degradation of complex substrates is involved, as well as a potential tool for the study of metabolic interactions in complex microbial communities.

微生物群落内部的代谢相互作用对于复杂有机化合物的高效降解至关重要，并且支撑着由微生物驱动的自然现象，比如含碳、氮和硫分子的循环。这些代谢相互作用最终决定了群落的功能、活性和稳定性，因此了解它们对于调控涉及微生物群落的过程至关重要。这在微生物燃料电池（MFCs）的设计中得到了应用，微生物燃料电池是一种生物电化学装置，它通过微生物（单一物种或群落）的代谢活动将底物中存在的化学能转化为电能。在这项工作中，我们分析了接种了厌氧微生物群落并持续供给复杂培养基的一系列微生物燃料电池中微生物群落结构的演变。对阳极群落组成的分析揭示了在水力连接的微生物燃料电池的阳极中形成了不同的群落，发酵类群的丰度沿电池组降低，而呼吸类群的丰度同时增加。对阳极悬浮液中代谢产物的分析表明，第一个和最后一个微生物燃料电池之间存在代谢转变，证实了阳极群落的分离。这些结果表明，在电池组的早期阶段占主导地位的发酵细菌与后期阶段的厌氧呼吸产电菌群之间存在一种代谢相互作用机制，这反映在观察到的功率输出增加上。我们表明，我们的实验系统是优化涉及复杂底物降解过程的理想平台，也是研究复杂微生物群落中代谢相互作用的潜在工具。