Hallinen Kelsey M, Bodine Steven P, Stone Howard A, Muir Tom W, Wingreen Ned S, Gitai Zemer
Department of Physics, Princeton University, Princeton, NJ 08544.
Department of Chemistry, Princeton University, Princeton, NJ 08544.
Proc Natl Acad Sci U S A. 2025 Feb 18;122(7):e2419899122. doi: 10.1073/pnas.2419899122. Epub 2025 Feb 10.
Fluid flows are dominant features of many bacterial environments, and flow can often impact bacterial behaviors in unexpected ways. For example, the most common type of cardiovascular infection is heart valve colonization by gram-positive bacteria like and (endocarditis). This behavior is counterintuitive because heart valves experience high shear rates that would naively be expected to reduce colonization. To determine whether these bacteria preferentially colonize higher shear rate environments, we developed a microfluidic system to quantify the effect of flow conditions on the colonization of and . We find that the preferential colonization in high flow of both species is not specific to heart valves and can be found in simple configurations lacking any host factors. This behavior enables bacteria that are outcompeted in low flow to dominate in high flow. Surprisingly, experimental and computational studies reveal that the two species achieve this behavior via distinct mechanisms. grows in cell clusters and produces a dispersal signal whose transport is affected by shear rate. Meanwhile, grows in linear chains whose mechanical properties result in less dispersal in the presence of higher shear force. In addition to establishing two divergent mechanisms by which these bacteria each preferentially colonize high-flow environments, our findings highlight the importance of understanding bacterial behaviors at the level of collective interactions among cells. These results suggest that distinct multicellular nanocolony morphologies have previously unappreciated costs and benefits in different environments, like those introduced by fluid flow.
流体流动是许多细菌生存环境的主要特征，而且流动常常会以意想不到的方式影响细菌的行为。例如，最常见的心血管感染类型是革兰氏阳性菌如 和 （心内膜炎）在心脏瓣膜上的定植。这种行为有悖常理，因为心脏瓣膜处的剪切速率很高，直观上人们会认为这会减少细菌的定植。为了确定这些细菌是否优先定殖于较高剪切速率的环境中，我们开发了一种微流控系统来量化流动条件对 和 定殖的影响。我们发现，这两种细菌在高流速下的优先定殖并非心脏瓣膜所特有，在缺乏任何宿主因素的简单结构中也能观察到。这种行为使得在低流速下竞争力较弱的细菌在高流速下占据主导地位。令人惊讶的是，实验和计算研究表明，这两种细菌通过不同的机制实现这种行为。 以细胞簇的形式生长，并产生一种扩散信号，其传输受剪切速率的影响。与此同时， 以线性链的形式生长，其机械特性导致在较高剪切力存在时扩散较少。除了确定这两种细菌各自优先定殖于高流速环境的两种不同机制外，我们的研究结果还强调了在细胞间集体相互作用层面理解细菌行为的重要性。这些结果表明，不同的多细胞纳米菌落形态在不同环境中，如由流体流动引入的环境中，有着此前未被认识到的成本和益处。
