Division of Microbial Ecology, Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria.
Max Planck Institute for Marine Microbiology, Bremen, Germany.
ISME J. 2021 Jan;15(1):348-353. doi: 10.1038/s41396-020-00761-5. Epub 2020 Sep 2.
Stable isotope probing (SIP) is a key tool for identifying the microorganisms catalyzing the turnover of specific substrates in the environment and to quantify their relative contributions to biogeochemical processes. However, SIP-based studies are subject to the uncertainties posed by cross-feeding, where microorganisms release isotopically labeled products, which are then used by other microorganisms, instead of incorporating the added tracer directly. Here, we introduce a SIP approach that has the potential to strongly reduce cross-feeding in complex microbial communities. In this approach, the microbial cells are exposed on a membrane filter to a continuous flow of medium containing isotopically labeled substrate. Thereby, metabolites and degradation products are constantly removed, preventing consumption of these secondary substrates. A nanoSIMS-based proof-of-concept experiment using nitrifiers in activated sludge and C-bicarbonate as an activity tracer showed that Flow-SIP significantly reduces cross-feeding and thus allows distinguishing primary consumers from other members of microbial food webs.
稳定同位素探测（SIP）是一种识别环境中特定基质转化的微生物，并定量其对生物地球化学过程相对贡献的关键工具。然而，基于 SIP 的研究受到交叉喂养的不确定性的影响，其中微生物释放同位素标记产物，然后被其他微生物利用，而不是直接将添加的示踪剂掺入。在这里，我们介绍了一种 SIP 方法，该方法有可能在复杂的微生物群落中大大减少交叉喂养。在这种方法中，微生物细胞暴露在含有同位素标记底物的连续流动的培养基膜过滤器上。由此，代谢物和降解产物被不断去除，防止这些次级底物的消耗。使用活性污泥中的硝化菌和 C-碳酸氢盐作为活性示踪剂的基于 nanoSIMS 的概念验证实验表明，Flow-SIP 显著减少了交叉喂养，从而可以区分初级消费者和微生物食物网的其他成员。
