Tang Yangyang, Zhang Zheng, Tao Cong, Wang Xiaoling
School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China.
Biomicrofluidics. 2024 May 6;18(3):034103. doi: 10.1063/5.0203061. eCollection 2024 May.
Biofilms are communities formed by bacteria adhering to surfaces, widely present in porous medium, and their growth can lead to clogging. Our experiment finds that under certain flow conditions, biofilms detach in pores and form a dynamically changing flow path. We define detachment that occurs far from the boundary of the flow path (with a distance greater than 200 m) as internal detachment and detachment that occurs at the boundary of the flow path as external detachment. To understand the mechanism of biofilm detachment, we study the detachment behaviors of the biofilm in a porous medium in a microfluidic device, where strain is triple fluorescent labeled, which can represent three main phenotypes during the biofilm formation: motile cells, matrix-producing cells, and spores. We find that slow small-scale internal detachment occurs in regions with very few motile cells and matrix-producing cells, and bacterial movement in these areas is disordered. The increase in the number of matrix-producing cells induces clogging, and after clogging, the rapid detachment of the bulk internal biofilm occurs due to the increased pressure difference at the inlet and outlet. When both internal and external detachments occur simultaneously, the number of matrix-producing cells in the internal detachment area is 2.5 times that in the external detachment area. The results indicate that biofilm detachment occurs in areas with fewer matrix-producing cells, as matrix-producing cells can help resist detachment by secreting extracellular polymeric substances (EPSs).
生物膜是细菌附着于表面形成的群落，广泛存在于多孔介质中，其生长会导致堵塞。我们的实验发现，在一定流动条件下，生物膜在孔隙中脱落并形成动态变化的流动路径。我们将发生在远离流动路径边界（距离大于200米）的脱落定义为内部脱落，将发生在流动路径边界的脱落定义为外部脱落。为了理解生物膜脱落的机制，我们在微流控装置中研究了多孔介质中生物膜的脱落行为，其中菌株用三重荧光标记，可代表生物膜形成过程中的三种主要表型：运动细胞、产基质细胞和孢子。我们发现，在运动细胞和产基质细胞极少的区域会发生缓慢的小规模内部脱落，这些区域的细菌运动无序。产基质细胞数量的增加会导致堵塞，堵塞后，由于进出口压差增大，大量内部生物膜会迅速脱落。当内部和外部脱落同时发生时，内部脱落区域的产基质细胞数量是外部脱落区域的2.5倍。结果表明，生物膜脱落发生在产基质细胞较少的区域，因为产基质细胞可以通过分泌胞外聚合物（EPS）来帮助抵抗脱落。
