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Mechanics limits ecological diversity and promotes heterogeneity in confined bacterial communities
Proceedings of the National Academy of Sciences of the United States of America ( IF 11.1 ) Pub Date : 2024-05-10 , DOI: 10.1073/pnas.2322321121
Tianyi Ma 1, 2 , Jeremy Rothschild 1 , Faisal Halabeya 1, 2 , Anton Zilman 1 , Joshua N. Milstein 1, 2
Affiliation  

Multispecies bacterial populations often inhabit confined and densely packed environments where spatial competition determines the ecological diversity of the community. However, the role of mechanical interactions in shaping the ecology is still poorly understood. Here, we study a model system consisting of two populations of nonmotile Escherichia coli bacteria competing within open, monolayer microchannels. The competitive dynamics is observed to be biphasic: After seeding, either one strain rapidly fixates or both strains orient into spatially stratified, stable communities. We find that mechanical interactions with other cells and local spatial constraints influence the resulting community ecology in unexpected ways, severely limiting the overall diversity of the communities while simultaneously allowing for the establishment of stable, heterogeneous populations of bacteria displaying disparate growth rates. Surprisingly, the populations have a high probability of coexisting even when one strain has a significant growth advantage. A more coccus morphology is shown to provide a selective advantage, but agent-based simulations indicate this is due to hydrodynamic and adhesion effects within the microchannel and not from breaking of the nematic ordering. Our observations are qualitatively reproduced by a simple Pólya urn model, which suggests the generality of our findings for confined population dynamics and highlights the importance of early colonization conditions on the resulting diversity and ecology of bacterial communities. These results provide fundamental insights into the determinants of community diversity in dense confined ecosystems where spatial exclusion is central to competition as in organized biofilms or intestinal crypts.

中文翻译:

力学限制了生态多样性并促进了有限细菌群落的异质性

多物种细菌种群通常栖息在有限且密集的环境中,其中空间竞争决定了群落的生态多样性。然而,机械相互作用在塑造生态中的作用仍然知之甚少。在这里,我们研究了一个由两个非运动群体组成的模型系统大肠杆菌细菌在开放的单层微通道内竞争。观察到竞争动态是双相的:播种后,任一菌株迅速固定,或两种菌株都定向形成空间分层的稳定群落。我们发现,与其他细胞的机械相互作用和局部空间限制以意想不到的方式影响所产生的群落生态,严重限制了群落的整体多样性,同时允许建立显示不同生长速率的稳定、异质的细菌群体。令人惊讶的是,即使一种菌株具有显着的生长优势,种群共存的可能性也很高。更多的球菌形态显示出提供了选择性优势,但基于试剂的模拟表明这是由于微通道内的流体动力学和粘附效应而不是向列有序的破坏。我们的观察结果通过一个简单的 Pólya 瓮模型进行了定性再现,这表明我们的研究结果对于有限的种群动态具有普遍性,并强调了早期定植条件对细菌群落多样性和生态学的重要性。这些结果为密集密闭生态系统中群落多样性的决定因素提供了基本见解,在这些生态系统中,空间排斥是竞争的核心,如有组织的生物膜或肠隐窝。
更新日期:2024-05-10
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