On Single-Cell Enzyme Assays in Marine Microbial Ecology and Biogeochemistry
On Single-Cell Enzyme Assays in Marine Microbial Ecology and Biogeochemistry
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DOI：
10.3389/fmars.2022.846656
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发表时间：
2022-02
期刊：
影响因子：
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通讯作者：
Sachia J. Traving;J. Balmonte;D. Seale;C. Arnosti;R. Glud;S. Hallam;M. Middelboe
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文献类型：
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作者：
Sachia J. Traving;J. Balmonte;D. Seale;C. Arnosti;R. Glud;S. Hallam;M. Middelboe
胞外酶活性是评价微生物在海洋生态系统中的生物地球化学作用的公认参数。海水中胞外酶的存在和活性提供了对目前微生物正在处理的有机物的质量和数量的洞察。在我们理解这些过程中的一个关键挑战是在单细胞水平上破译自然群落的胞外酶谱和活性。目前的测量是在大宗或大小分级样本上进行的，以捕捉混合种群的活动。这种方法--即使是按大小分级--也不能用来追踪酶的产生者，也不能区分活跃的微生物成员，从而导致测量的活动和产生细胞之间的脱节。通过以胞外酶为靶点并在单细胞水平上分解它们的活性，我们可以研究克隆或密切相关生物之间潜在的表型异质性，表征不同环境条件下的酶动力学，并解决自然群落中单个酶产生者的时空分布。在这篇透视文章中，我们讨论了微流控液滴和原核细胞功能筛选领域的最新技术，以一次一个细胞地测量海洋海水样本中的酶活性。我们进一步阐述了如何使用这种单细胞方法来解决目前方法无法回答的研究问题，如与海洋微生物对有机物的酶降解有关的问题。
Extracellular enzyme activity is a well-established parameter for evaluating microbial biogeochemical roles in marine ecosystems. The presence and activity of extracellular enzymes in seawater provide insights into the quality and quantity of organic matter being processed by the present microorganisms. A key challenge in our understanding of these processes is to decode the extracellular enzyme repertoire and activities of natural communities at the single-cell level. Current measurements are carried out on bulk or size-fractionated samples capturing activities of mixed populations. This approach – even with size-fractionation – cannot be used to trace enzymes back to their producers, nor distinguish the active microbial members, leading to a disconnect between measured activities and the producer cells. By targeting extracellular enzymes and resolving their activities at the single-cell level, we can investigate underlying phenotypic heterogeneity among clonal or closely related organisms, characterize enzyme kinetics under varying environmental conditions, and resolve spatio-temporal distribution of individual enzyme producers within natural communities. In this perspective piece, we discuss state-of-the-art technologies in the fields of microfluidic droplets and functional screening of prokaryotic cells for measuring enzyme activity in marine seawater samples, one cell at a time. We further elaborate on how this single-cell approach can be used to address research questions that cannot be answered with current methods, as pertinent to the enzymatic degradation of organic matter by marine microorganisms.