Roush Caroline J, Lastoskie Christian M, Worden R Mark
Department of Chemical Engineering, Michigan State University, East Lansing, 48824-1226, USA.
J Environ Sci Health A Tox Hazard Subst Environ Eng. 2006;41(6):967-83. doi: 10.1080/10934520600689258.
Chemotaxis is an important mechanism by which microorganisms are dispersed in porous media. A vigorous chemotactic response to concentration gradients formed by microbial consumption of chemoattractants can accelerate transport of bacteria to highly contaminated regions of soils and sediments, enhancing the efficiency of in situ bioremediation operations. Although chemotaxis plays a key role in establishment of biodegradation zones in the subsurface, the effects of physical heterogeneity on bacterial motility are poorly understood. To investigate the influence of porous media heterogeneity on microbial chemotaxis, swarm plate migration experiments were conducted using Pseudomonas stutzeri strain KC, a denitrifying bacterium used for in situ biodegradation of carbon tetrachloride in groundwater. Swarm plate measurements indicate that strain KC is strongly chemotactic toward both acetate and nitrate. A three-component mathematical model was developed to describe the migration of strain KC. Estimates of chemotactic sensitivity were obtained in the homogeneous (agar) phase and in a heterogeneous medium of aquifer solids extracted from the Schoolcraft bioremediation field site in western Michigan. Interestingly, the motility of strain KC is significantly larger in the porous medium than in the aqueous phase. We hypothesize that chemotactic response is enhanced within the heterogeneous medium because chemoattractant gradients formed by nitrate consumption are larger in the confined spaces of the porous medium than in unconfined agar solution.
趋化作用是微生物在多孔介质中扩散的一种重要机制。对由微生物消耗化学引诱剂形成的浓度梯度产生强烈的趋化反应，可以加速细菌向土壤和沉积物中高污染区域的迁移，提高原位生物修复操作的效率。尽管趋化作用在地下生物降解带的形成中起着关键作用，但物理非均质性对细菌运动性的影响却知之甚少。为了研究多孔介质非均质性对微生物趋化作用的影响，使用施氏假单胞菌菌株KC进行了群体平板迁移实验，该菌株是一种用于地下水中四氯化碳原位生物降解的反硝化细菌。群体平板测量表明，菌株KC对乙酸盐和硝酸盐都有强烈的趋化作用。建立了一个三组分数学模型来描述菌株KC的迁移。在均质（琼脂）相中以及从密歇根州西部的斯库克拉夫特生物修复现场提取的含水层固体的非均质介质中获得了趋化敏感性估计值。有趣的是，菌株KC在多孔介质中的运动性明显大于在水相中。我们推测，在非均质介质中趋化反应会增强，因为在多孔介质的受限空间中由硝酸盐消耗形成的化学引诱剂梯度比在无限制的琼脂溶液中更大。
