Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States of America.
Bredesen Center, University of Tennessee, Knoxville, TN, United States of America.
PLoS One. 2019 Jun 27;14(6):e0218316. doi: 10.1371/journal.pone.0218316. eCollection 2019.
Bacteria occupy heterogeneous environments, attaching and growing within pores in materials, living hosts, and matrices like soil. Systems that permit high-resolution visualization of dynamic bacterial processes within the physical confines of a realistic and tractable porous media environment are rare. Here we use microfluidics to replicate the grain shape and packing density of natural sands in a 2D platform to study the flow-induced spatial evolution of bacterial biofilms underground. We discover that initial bacterial dispersal and grain attachment is influenced by bacterial transport across pore space velocity gradients, a phenomenon otherwise known as rheotaxis. We find that gravity-driven flow conditions activate different bacterial cell-clustering phenotypes depending on the strain's ability to product extracellular polymeric substances (EPS). A wildtype, biofilm-producing bacteria formed compact, multicellular patches while an EPS-defective mutant displayed a linked-cell phenotype in the presence of flow. These phenotypes subsequently influenced the overall spatial distribution of cells across the porous media network as colonies grew and altered the fluid dynamics of their microenvironment.
细菌栖息于异质环境中，在材料、活体宿主和土壤等基质的孔隙中附着和生长。能够在真实且易于处理的多孔介质环境的物理限制内对动态细菌过程进行高分辨率可视化的系统十分罕见。在这里，我们使用微流控技术在 2D 平台上复制天然砂的颗粒形状和堆积密度，以研究地下细菌生物膜的流动诱导的空间演化。我们发现，细菌的初始扩散和颗粒附着受到细菌在孔隙空间速度梯度中迁移的影响，这种现象也被称为流动趋性。我们发现，重力驱动的流动条件会根据菌株产生胞外聚合物物质（EPS）的能力激活不同的细菌细胞聚集表型。一个野生型、生物膜形成细菌形成了紧密的多细胞斑块，而在存在流动的情况下，EPS 缺陷突变体则表现出链接细胞表型。这些表型随后影响了细胞在多孔介质网络中的整体空间分布，因为菌落生长并改变了其微环境的流体动力学。
