Some food and ferment manufacturing steps such as spray-drying result in the application of viscous stresses to bacteria. This study explores how a viscous flow impacts both bacterial adhesion functionality and bacterial cell organization using a combined experimental and modeling approach. As a model organism we study Lactobacillus rhamnosus GG (LGG) “wild type” (WT), known to feature strong adhesive affinities towards beta-lactoglobulin thanks to pili produced by the bacteria on cell surfaces, along with three cell-surface mutant strains. Applying repeated flows with high shear-rates reduces bacterial adhesive abilities up to 20% for LGG WT. Bacterial chains are also broken by this process, into 2-cell chains at low industrial shear rates, and into single cells at very high shear rates. To rationalize the experimental observations we study numerically and analytically the Stokes equations describing viscous fluid flow around a chain of elastically connected spheroidal cell bodies. In this model setting we examine qualitatively the relationship between surface traction (force per unit area), a proxy for pili removal rate, and bacterial chain length (number of cells). Longer chains result in higher maximal surface tractions, particularly at the chain extremities, while inner cells enjoy a small protection from surface tractions due to hydrodynamic interactions with their neighbors. Chain rupture therefore may act as a mechanism to preserve surface adhesive functionality in bacteria.

中文翻译：

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用粘性流剃刮和破坏细菌链。

一些食品和发酵生产步骤（例如喷雾干燥）会导致对细菌施加粘性压力。这项研究探索了粘性流如何使用组合的实验和建模方法来影响细菌粘附功能和细菌细胞组织。作为模型生物，我们研究鼠李糖乳杆菌GG（LGG）“野生型”（WT），由于细菌在细胞表面产生的菌毛以及三种细胞表面突变株，对β-乳球蛋白具有很强的粘合亲和力。对LGG WT施加高剪切速率的重复流可将细菌粘附能力降低多达20％。细菌链也通过该过程断裂，在低工业剪切速率下分解为2个单元的链，并在非常高剪切速率下分解为单个单元。为了使实验观察合理化，我们在数值和分析角度上研究了描述粘性流体绕弹性连接的球形细胞体链流动的斯托克斯方程。在此模型设置中，我们定性地研究了表面牵引力（每单位面积的力），菌毛去除率的代用物和细菌链长（细胞数）之间的关系。较长的链会导致较高的最大表面牵引力，尤其是在链的末端，而内部细胞由于与邻居之间的流体动力学相互作用而受到较小的保护，免受表面牵引力的影响。因此，链断裂可以充当保持细菌中表面粘附功能的机制。