Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Permoserstraße 15, D-04318 Leipzig, Germany.
J Theor Biol. 2011 Oct 21;287:82-91. doi: 10.1016/j.jtbi.2011.07.024. Epub 2011 Aug 3.
The spatio-temporal distribution of subsurface microorganisms determines their efficiency in providing essential ecosystem services such as the degradation of organic matter, the remineralization of carbon and nitrogen, or the remediation of anthropogenic contaminants. Populations of motile, chemotactic bacteria have been shown to be capable of pattern formation even in the absence of environmental heterogeneities. Focusing on the water saturated domain of the subsurface (e.g., aquatic sediments, porous aquifers), we analyze this innate capability of bacterial populations in an idealized model of a homogeneous, saturated porous medium. Considering a linear array of connected, identical microhabitats populated by motile, chemotactic bacterial cells, we identify prerequisites for pattern formation, analyze types of patterns, and assess their impact on substrate utilization. In our model, substrate supplied to the microhabitats facilitates bacterial growth, and microbial cells can migrate between neighboring microhabitats due to (i) random motility, (ii) chemotaxis towards substrate, and (iii) self-attraction. A precondition for inhomogeneous population patterns is analytically derived, stating that patterns are possible if the self-attraction exceeds a threshold defined by the random motility and the steady state population density in the microhabitats. An individual-based implementation of the model shows that static and dynamic population patterns can unfold. Degradation efficiency is highest for homogeneous bacterial distributions and decreases as pattern formation commences. If during biostimulation efforts the carrying capacity of the microhabitats is successively increased, simulation results show that degradation efficiency can unexpectedly decrease when the pattern formation threshold is crossed.
地下微生物的时空分布决定了它们在提供基本生态系统服务方面的效率，例如有机物的降解、碳和氮的再矿化，或人为污染物的修复。已证明，即使在不存在环境异质性的情况下，运动的、趋化的细菌种群也能够形成模式。本研究集中于地下的饱和水区域（例如水生沉积物、多孔含水层），我们在均匀饱和多孔介质的理想化模型中分析了细菌种群的这种固有能力。考虑由运动的、趋化的细菌细胞组成的连接的、相同的微生境的线性阵列，我们确定了形成模式的前提条件，分析了模式的类型，并评估了它们对基质利用的影响。在我们的模型中，供应给微生境的基质促进了细菌的生长，并且由于以下三种情况，微生物细胞可以在相邻的微生境之间迁移：（i）随机运动，（ii）向基质的趋化性，和（iii）自吸引。不均匀的种群模式的一个前提条件是通过分析得出的，即如果自吸引超过了由随机运动和微生境中的稳态种群密度定义的阈值，则可以形成模式。该模型的基于个体的实现表明，可以展开静态和动态的种群模式。均匀的细菌分布具有最高的降解效率，而随着模式形成的开始，降解效率降低。如果在生物刺激努力中，微生境的承载能力依次增加，则模拟结果表明，当达到模式形成阈值时，降解效率会出人意料地降低。
