Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America.
PLoS One. 2022 Mar 31;17(3):e0266282. doi: 10.1371/journal.pone.0266282. eCollection 2022.
Co-cultivation in microfluidic droplets has emerged as a versatile tool for the study of natural and synthetic microbial communities. In particular, the identification and characterization of syntrophic interactions in these communities is attracting increasing interest due to their critical importance for the functioning of environmental and host-associated communities as well as new biotechnological applications. However, one critical parameter in droplet-enabled co-cultivation that has evaded appropriate evaluation is the droplet size. Given the same number of initial cells, a larger droplet size can increase the length scale secreted metabolites must diffuse as well as dilute the initial concentration of cells and exchanged metabolites, impacting the community dynamics. To evaluate the effect of droplet size on a spectrum of syntrophic interactions, we cultivated a synthetic model system consisting of two E. coli auxotrophs, whose interactions could be modulated through supplementation of related amino acids in the medium. Our results demonstrate that the droplet size impacts substantially numerous aspects of the growth of a cross-feeding bi-culture, particularly the growth capacity, maximum specific growth rate, and lag time, depending on the degree of the interaction. This work heavily suggests that one droplet size does not fit all types of interactions; this parameter should be carefully evaluated and chosen in experimental studies that aim to utilize droplet-enabled co-cultivation to characterize or elucidate microbial interactions.
共培养在微流控液滴中已经成为研究自然和合成微生物群落的一种通用工具。特别是，由于这些群落中的协同相互作用对于环境和宿主相关群落的功能以及新的生物技术应用至关重要，因此对这些群落中的协同相互作用进行鉴定和表征越来越受到关注。然而，在基于液滴的共培养中，一个关键参数一直未能得到适当的评估，那就是液滴的大小。在相同数量的初始细胞的情况下，较大的液滴尺寸可以增加代谢物必须扩散的长度尺度，同时稀释初始细胞浓度和交换代谢物的浓度，从而影响群落动力学。为了评估液滴大小对一系列协同相互作用的影响，我们培养了一个由两种大肠杆菌营养缺陷型组成的合成模型系统，通过在培养基中补充相关的氨基酸，可以调节它们之间的相互作用。我们的结果表明，液滴大小对交叉喂养双培养的生长有很大的影响，特别是生长能力、最大比生长速率和迟滞时间，这取决于相互作用的程度。这项工作强烈表明，一种液滴大小并不适用于所有类型的相互作用；在旨在利用基于液滴的共培养来表征或阐明微生物相互作用的实验研究中，应该仔细评估和选择这个参数。
