Migration of Chemotactic Bacteria in Soft Agar: Role of Gel Concentration
Migration of Chemotactic Bacteria in Soft Agar: Role of Gel Concentration
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DOI：
10.1016/j.bpj.2011.06.023
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发表时间：
2011-08-03
影响因子：
3.4
通讯作者：
Poon, Wilson C. K.
中科院分区：
文献类型：
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作者：
Croze, Ottavio A.;Ferguson, Gail P.;Poon, Wilson C. K.
我们研究了在浓度范围C = 0.15-0.5%（w/v）的半固体（软）琼脂中趋化性野生型大肠杆菌种群的迁移。对于小于或接近0.35%的C，扩增的细菌菌落显示出特征性的趋化环。然而，在C = 0.35%时，细菌以宽的环形带而不是尖锐的环迁移。这些是生长/扩散波，因为抑制由琼脂的趋化性，并没有以前的实验报告，以我们的知识。对于C = 0.4- 0.5%，扩增菌落不跨越琼脂的深度，并产生明显的前沿不稳定性。在C <0.25%时，迁移前沿速度对琼脂浓度的依赖性较弱，但在此值以上时急剧下降。我们讨论了这些意见，在一个扩展的凯勒-西格尔模型，我们推导出新的传输参数表达式占扰动的趋化反应与琼脂的碰撞。该模型使得有可能适合所观察到的前速度衰减的范围C= 0.15- 0.35%，其解决方案定性地再现所观察到的从趋化性到生长/扩散带的过渡。我们讨论了多孔介质中的细菌的研究和改进的细菌趋化性测定的设计，我们的研究结果的影响。
We study the migration of chemotactic wild-type Escherichia colt populations in semisolid (soft) agar in the concentration range C = 0.15-0.5% (w/v). For C less than or similar to 0.35%, expanding bacterial colonies display characteristic chemotactic rings. At C = 0.35%, however, bacteria migrate as broad circular bands rather than sharp rings. These are growth/diffusion waves arising because of suppression of chemotaxis by the agar and have not been previously reported experimentally to our knowledge. For C = 0.4-0.5%, expanding colonies do not span the depth of the agar and develop pronounced front instabilities. The migration front speed is weakly dependent on agar concentration at C < 0.25%, but decreases sharply above this value. We discuss these observations in terms of an extended Keller-Segel model for which we derived novel transport parameter expressions accounting for perturbations of the chemotactic response by collisions with the agar. The model makes it possible to fit the observed front speed decay in the range C= 0.15-0.35%, and its solutions qualitatively reproduce the observed transition from chemotactic to growth/diffusion bands. We discuss the implications of our results for the study of bacteria in porous media and for the design of improved bacteriological chemotaxis assays.