Soil and Terrestrial Environmental Physics (STEP), Institute of Terrestrial Ecosystems (ITES), ETH Zurich, Zurich, Switzerland.
Environ Microbiol. 2010 May;12(5):1363-73. doi: 10.1111/j.1462-2920.2010.02180.x. Epub 2010 Feb 25.
Bacterial motility is a key mechanism for survival in a patchy environment and is important for ecosystem biodiversity maintenance. Quantitative description of bacterial motility in soils is hindered by inherent heterogeneity, pore-space complexity and dynamics of microhydrological conditions. Unsaturated conditions result in fragmented aquatic habitats often too small to support full bacterial immersion thereby forcing strong interactions with mineral and air interfaces that significantly restrict motility. A new hybrid model was developed to study hydration effects on bacterial motility. Simulation results using literature parameter values illustrate sensitivity of colony expansion rates to hydration conditions and are in general agreement with measured values. Under matric potentials greater than -0.5 kPa (wet), bacterial colonies grew fast at colony expansion rates exceeding 421 +/- 94 microm h(-1); rates dropped significantly to 31 +/- 10 microm h(-1) at -2 kPa; as expected, no significant colony expansion was observed at -5 kPa because of the dominance of capillary pinning forces in the submicrometric water film. Quantification of hydration-related constraints on bacterial motion provides insights into optimal conditions for bacterial dispersion and spatial ranges of resource accessibility important for bioremediation and biogeochemical cycles. Results define surprisingly narrow range of hydration conditions where motility confers ecological advantage on natural surfaces.
细菌的运动性是其在斑块环境中生存的关键机制，对维持生态系统生物多样性也很重要。由于土壤固有的异质性、孔隙空间的复杂性以及微水条件的动态变化，定量描述土壤中细菌的运动性受到了阻碍。非饱和条件会导致水生栖息地碎片化，这些栖息地通常太小，无法支持细菌完全浸入，从而迫使细菌与矿物和空气界面发生强烈相互作用，这大大限制了细菌的运动性。我们开发了一种新的混合模型来研究水合作用对细菌运动性的影响。使用文献参数值进行的模拟结果表明，菌落扩展率对水合条件很敏感，并且与实测值大体一致。在基质势大于-0.5 kPa（湿）时，细菌菌落以超过 421 ± 94 µm h(-1)的菌落扩展率快速生长；在-2 kPa 时，速度显著下降到 31 ± 10 µm h(-1)；由于亚微米水膜中的毛细钉扎力占主导地位，预计在-5 kPa 时不会发生明显的菌落扩展。量化水合作用对细菌运动的限制，可以深入了解细菌分散的最佳条件以及资源可及性的空间范围，这对生物修复和生物地球化学循环都很重要。研究结果定义了一个令人惊讶的狭窄水合条件范围，在此范围内，运动性赋予了自然表面生态优势。
