Communities of interacting microorganisms play important roles across all habitats on Earth. These communities typically consist of a large number of species that perform different metabolic processes. The functions of microbial communities ultimately emerge from interactions between these different microorganisms. To understand the dynamics and functions of microbial communities, we thus need to know the nature and strength of these interactions. Here, we quantified the interaction strength between individual cells in microbial communities. We worked with synthetic communities of Escherichia coli bacteria that exchange metabolites to grow. We combined single-cell growth rate measurements with mathematical modelling to quantify metabolic interactions between individual cells and to map the spatial interaction network in these communities. We found that cells only interact with other cells in their immediate neighbourhood. This short interaction range limits the coupling between different species and reduces their ability to perform metabolic processes collectively. Our experiments and models demonstrate that the spatial scale of biotic interaction plays a fundamental role in shaping the ecological dynamics of communities and the functioning of ecosystems.

相互作用的微生物群落在地球上的所有栖息地中发挥着重要作用。这些群落通常由大量执行不同代谢过程的物种组成。微生物群落的功能最终来自这些不同微生物之间的相互作用。为了了解微生物群落的动态和功能，我们需要了解这些相互作用的性质和强度。在这里，我们量化了微生物群落中单个细胞之间的相互作用强度。我们与大肠杆菌的合成群落合作交换代谢物以生长的细菌。我们将单细胞生长速率测量与数学模型相结合，以量化单个细胞之间的代谢相互作用并绘制这些群落中的空间相互作用网络。我们发现细胞只与附近的其他细胞相互作用。这种短的相互作用范围限制了不同物种之间的耦合，并降低了它们共同执行代谢过程的能力。我们的实验和模型表明，生物相互作用的空间尺度在塑造群落的生态动态和生态系统的功能方面发挥着重要作用。