Department of Fundamental Microbiology, University of Lausanne, CH-1015, Lausanne, Switzerland.
Department of Mathematics, University of Fribourg, CH-1700, Fribourg, Switzerland.
Nat Commun. 2024 Aug 31;15(1):7591. doi: 10.1038/s41467-024-51944-z.
Bacteria in nature often thrive in fragmented environments, like soil pores, plant roots or plant leaves, leading to smaller isolated habitats, shared with fewer species. This spatial fragmentation can significantly influence bacterial interactions, affecting overall community diversity. To investigate this, we contrast paired bacterial growth in tiny picoliter droplets (1-3 cells per 35 pL up to 3-8 cells per species in 268 pL) with larger, uniform liquid cultures (about 2 million cells per 140 µl). We test four interaction scenarios using different bacterial strains: substrate competition, substrate independence, growth inhibition, and cell killing. In fragmented environments, interaction outcomes are more variable and sometimes even reverse compared to larger uniform cultures. Both experiments and simulations show that these differences stem mostly from variation in initial cell population growth phenotypes and their sizes. These effects are most significant with the smallest starting cell populations and lessen as population size increases. Simulations suggest that slower-growing species might survive competition by increasing growth variability. Our findings reveal how microhabitat fragmentation promotes diverse bacterial interaction outcomes, contributing to greater species diversity under competitive conditions.
自然界中的细菌通常在碎片化的环境中茁壮成长，例如土壤孔隙、植物根系或植物叶片中，这些环境形成了更小的孤立栖息地，与较少的物种共享。这种空间碎片化会显著影响细菌的相互作用，影响整体群落的多样性。为了研究这一点，我们对比了在微小皮升级别的液滴（每 35 微升中有 1-3 个细胞，在 268 微升中每个物种有 3-8 个细胞）和更大、均匀的液体培养物（每 140 微升中有约 200 万个细胞）中配对细菌的生长情况。我们使用不同的细菌菌株测试了四种相互作用情景：基质竞争、基质独立性、生长抑制和细胞杀伤。在碎片化的环境中，与较大的均匀培养物相比，相互作用的结果更加多变，有时甚至相反。实验和模拟都表明，这些差异主要源自初始细胞群体生长表型及其大小的变化。这些影响在最小的起始细胞群体中最为显著，随着种群规模的增加而减弱。模拟表明，生长较慢的物种可能通过增加生长变异性来在竞争中存活。我们的发现揭示了微生境碎片化如何促进多样化的细菌相互作用结果，有助于在竞争条件下增加物种多样性。
