Nambi Indumathi M, Werth Charles J, Sanford Robert A, Valocchi Albert J
Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 205 North Mathews Avenue, Urbana, Illinois 61801, USA.
Environ Sci Technol. 2003 Dec 15;37(24):5617-24. doi: 10.1021/es034271w.
The anaerobic halorespiring microorganism, Sulfurospirillum multivorans, was observed in the pore structure of an etched silicon wafer to determine how flow hydrodynamics and mass transfer limitations along a transverse mixing zone affect biomass growth. Tetrachloroethene (PCE, an electron acceptor, 0.2 mM) and lactate (an electron donor, 2 mM) were introduced as two separate and parallel streams that mixed along a reaction line in the pore structure. The first visible biomass occupied a single line of pores in the direction of flow, a few pore bodies from the micromodel centerline. This growth was initially present as small aggregates; over time, these grew and fused to form finger-like structures with one end attached to downgradient ends of the silicon posts and the other end extending into pore bodies in the direction of flow. Biomass did not grow in pore throats as expected, presumably because shear forces were not favorable. Over the next few weeks, the line of growth migrated upward into the PCE zone and extended over a width of up to five pore spaces. When the PCE concentration was increased to 0.5 mM, the microbial biomass increased and growth migrated down toward the lactate side of the micromodel. A new analytical model was developed and used to demonstrate that transverse hydrodynamic dispersion likely caused the biomass to move in the direction observed when the PCE concentration was changed. The model was unable, however, to explain why growth migrated upward when the PCE concentration was initially constant. We postulate that this occurred because PCE, not lactate, sorbed to biofilm components and that biomass on the lactate side of the micromodel was limited in PCE. A fluorescent tracer experiment showed that biomass growth changed the water flow paths, creating a higher velocity zone in the PCE half of the micromodel. These results contribute to our understanding of biofilm growth and will help in the development of new models to describe this complex process.
在蚀刻硅片的孔隙结构中观察到厌氧卤呼吸微生物——多食硫螺旋菌，以确定沿横向混合区的流动流体动力学和传质限制如何影响生物量的生长。四氯乙烯（PCE，一种电子受体，0.2 mM）和乳酸（一种电子供体，2 mM）作为两条分开且平行的流引入，它们在孔隙结构中沿反应线混合。最初可见的生物量在流动方向上占据了一排孔隙，距离微模型中心线有几个孔隙体。这种生长最初以小聚集体形式出现；随着时间的推移，这些聚集体生长并融合形成手指状结构，一端附着在硅柱的下游端，另一端沿流动方向延伸到孔隙体中。生物量并未如预期在孔隙喉部生长，大概是因为剪切力不利。在接下来的几周里，生长线向上迁移到PCE区域，并扩展到宽度达五个孔隙空间。当PCE浓度增加到0.5 mM时，微生物生物量增加，生长向下迁移到微模型的乳酸一侧。开发了一个新的分析模型，用于证明当PCE浓度改变时，横向流体动力弥散可能导致生物量沿观察到的方向移动。然而，该模型无法解释为什么当PCE浓度最初恒定时生长会向上迁移。我们推测这是因为PCE而非乳酸吸附到生物膜成分上，并且微模型乳酸一侧的生物量受到PCE的限制。荧光示踪实验表明，生物量的生长改变了水流路径，在微模型的PCE一侧形成了一个更高流速的区域。这些结果有助于我们理解生物膜的生长，并将有助于开发新的模型来描述这一复杂过程。
