Department of Ecology, Chemical Ecology and Ecotoxicology, University of Lund, Helgonavägen 5, S-223 62, Lund, Sweden.
Microb Ecol. 1991 Dec;21(1):49-72. doi: 10.1007/BF02539144.
Dispersal of bacteria in saturated, porous soils can be characterized by the partitioning of cells between the aqueous and solid phases, as a result of the physical and chemical nature of the soil and water and cell surface modifications. The purpose of this work is to understand variations in partitioning as a consequence of the nutrient conditions and to use this information in mathematical models to predict the dispersal rate of bacteria in aquifer material. Two different models were used to describe dispersal: an advective-dispersive-sorptive model with a first order kinetic sink term to account for irreversible cell reactions, such as death and sorption; and a two-site reaction model, in which the retardation was assumed to be determined by two types of sites, one characterized by instantaneous equilibrium sorption reactions and the other by kinetic nonequilibrium reactions. Water-saturated sand columns were used as continuous-flow groundwater microcosms to test the models under different nutrient regimes. Two strains of indigenous groundwater bacteria were isolated from aquifer material and labelled with(3)H-alanine,(14)C-pyruvic acid,(3)H-glucose, and(3)H-adenosine for different measurements of sorption and dispersal, which were estimated from breakthrough curves. Both experimental data and model variables showed that dispersal of bacteria was a dynamic nonequilibrium process, possibly shaped by two subpopulations, one strongly, even irreversibly, adsorbing to the solid particles, and one with very slow adsorption kinetics. The cell surfaces were modified in response to the growth conditions, which was demonstrated by hydrophobic and electrostatic interaction chromatography. Cell surface hydrophobicity was about eight times higher in groundwater than in eutrophic lake water. The partition coefficient varied between 12.6 in the groundwater and 6.4 in the lake water, indicating the prime importance of hydrophobic binding for attachment in low nutrient conditions. The partitioning was also sensitive to the hydrodynamics of the system and the oxygen supply, as demonstrated by comparison of sorption in agitated test tubes, gently shaken vials, and air-flushed bottles. Sorption kinetics were demonstrated in a continuous flow cell. About 45% of a population was associated with sand particles with a continuous flow of pure groundwater and as little as 20% in lake water. However, more than 50% of the bacteria in the aqueous phase were associated with suspended material of less than 60 μm in diameter. This association may enhance dispersal for example, by size exclusion of the colloidal material in the interstitial pores.
在饱和多孔土壤中，细菌的扩散可以通过细胞在水相与固相之间的分配来描述，这是由于土壤和水的物理化学性质以及细胞表面的修饰。这项工作的目的是了解分配的变化是由于营养条件的变化，并利用这些信息在数学模型中预测细菌在含水层物质中的扩散速率。使用了两种不同的模型来描述扩散：一种是具有一级动力学吸收项的对流-弥散-吸附模型，用于描述不可逆细胞反应，如死亡和吸附；另一种是双位点反应模型，其中延迟被认为是由两种类型的位点决定的，一种位点的特征是瞬时平衡吸附反应，另一种位点的特征是动力学非平衡反应。水饱和砂柱被用作连续流动的地下水微系统，以在不同的营养条件下测试模型。从含水层材料中分离出两种土著地下水细菌，并分别用（3）H-丙氨酸、（14）C-丙酮酸、（3）H-葡萄糖和（3）H-腺苷进行标记，用于不同的吸附和扩散测量，这些测量值是根据穿透曲线估计的。实验数据和模型变量都表明，细菌的扩散是一个动态的非平衡过程，可能由两个亚群形成，一个强烈地，甚至不可逆转地吸附到固体颗粒上，另一个则具有非常缓慢的吸附动力学。细胞表面在生长条件下发生了修饰，这可以通过疏水性和静电相互作用色谱来证明。与富营养化湖水相比，地下水的细胞表面疏水性高约 8 倍。分配系数在地下水和湖泊水中分别为 12.6 和 6.4，表明在低营养条件下，疏水性结合对附着非常重要。分配也对系统的水动力和氧气供应敏感，这可以通过比较在搅拌试管、轻轻摇动小瓶和空气冲洗瓶中的吸附来证明。在连续流细胞中证明了吸附动力学。在纯地下水流中，约有 45%的种群与砂粒结合，而在湖水中，这一比例仅为 20%。然而，在水相中，超过 50%的细菌与直径小于 60μm 的悬浮物质结合。这种结合可以增强扩散，例如通过对胶体物质在孔隙中的大小排除。
