Many bacterial habitats—ranging from gels and tissues in the body to cell-secreted exopolysaccharides in biofilms—are rheologically complex, undergo dynamic external forcing, and have unevenly distributed nutrients. How do these features jointly influence how the resident cells grow and proliferate? Here, we address this question by studying the growth of dispersed in granular hydrogel matrices with defined and highly tunable structural and rheological properties, under different amounts of external forcing imposed by mechanical shaking, and in both aerobic and anaerobic conditions. Our experiments establish a general principle: that the balance between the yield stress of the environment that the cells inhabit, , and the external stress imposed on the environment, , modulates bacterial growth by altering transport of essential nutrients to the cells. In particular, when , the environment is easily fluidized and mixed over large scales, providing nutrients to the cells and sustaining complete cellular growth. By contrast, when , the elasticity of the environment suppresses large-scale fluid mixing, limiting nutrient availability and arresting cellular growth. Our work thus reveals a new mechanism, beyond effects that change cellular behavior via local forcing, by which the rheology of the environment may modulate microbial physiology in diverse natural and industrial settings.

中文翻译：

---

环境产量和动态强迫之间的相互作用调节细菌生长

许多细菌栖息地——从体内的凝胶和组织到生物膜中细胞分泌的胞外多糖——流变学复杂，承受动态外力，并且营养物质分布不均匀。这些特征如何共同影响常驻细胞的生长和增殖？在这里，我们通过研究分散在颗粒状水凝胶基质中的生长来解决这个问题，这些基质具有明确的和高度可调的结构和流变特性，在机械振动施加的不同量的外力作用下，以及在有氧和厌氧条件下。我们的实验建立了一个一般原则：细胞居住环境的屈服应力 和施加在环境上的外部压力 之间的平衡，通过改变必需营养物质向细胞的运输来调节细菌生长。特别是，当 时，环境很容易大规模流化和混合，为细胞提供营养并维持细胞的完整生长。相比之下，当 时，环境的弹性会抑制大规模的流体混合，限制营养物质的可用性并阻止细胞生长。因此，我们的工作揭示了一种新的机制，超越通过局部强迫改变细胞行为的效应，通过这种机制，环境的流变学可以调节不同自然和工业环境中的微生物生理学。