1 Department of Environmental Systems Science, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich , Universitätstrasse 16, 8092 Zürich , Switzerland.
2 Department of Environmental Microbiology, Eawag , Überlandstrasse 133, 8600 Dübendorf , Switzerland.
J R Soc Interface. 2019 Jul 26;16(156):20190182. doi: 10.1098/rsif.2019.0182. Epub 2019 Jul 10.
Microbes live in ever-changing environments where they need to adapt their metabolism to different nutrient conditions. Many studies have characterized the response of genetically identical cells to nutrient switches in homogeneous cultures; however, in nature, microbes often live in spatially structured groups such as biofilms where cells can create metabolic gradients by consuming and releasing nutrients. Consequently, cells experience different local microenvironments and vary in their phenotype. How does this phenotypic variation affect the ability of cells to cope with nutrient switches? Here, we address this question by growing dense populations of Escherichia coli in microfluidic chambers and studying a switch from glucose to acetate at the single-cell level. Before the switch, cells vary in their metabolic activity: some grow on glucose, while others cross-feed on acetate. After the switch, only few cells can resume growth after a period of lag. The probability to resume growth depends on a cells' phenotype prior to the switch: it is highest for cells cross-feeding on acetate, while it depends in a non-monotonic way on the growth rate for cells growing on glucose. Our results suggest that the strong phenotypic variation in spatially structured populations might enhance their ability to cope with fluctuating environments.
微生物生活在不断变化的环境中，需要适应不同营养条件下的新陈代谢。许多研究已经描述了在同质培养物中，遗传上相同的细胞对营养物质转变的反应；然而，在自然界中，微生物通常生活在空间结构的群体中，如生物膜，在那里细胞可以通过消耗和释放营养物质来产生代谢梯度。因此，细胞经历不同的局部微环境，表型也会有所不同。这种表型变异如何影响细胞应对营养物质转变的能力？在这里，我们通过在微流控室中培养密集的大肠杆菌种群，并在单细胞水平上研究从葡萄糖到醋酸盐的转变来解决这个问题。在转变之前，细胞的代谢活性存在差异：一些细胞在葡萄糖上生长，而另一些细胞则通过醋酸盐进行交叉喂养。转变后，只有少数细胞在一段潜伏期后能够恢复生长。恢复生长的概率取决于细胞在转变前的表型：对于通过醋酸盐进行交叉喂养的细胞来说，概率最高，而对于在葡萄糖上生长的细胞来说，则取决于生长速率，呈非单调关系。我们的结果表明，在空间结构群体中强烈的表型变异可能增强了它们应对波动环境的能力。
