Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan 48824, United States.
Environ Sci Technol. 2011 Feb 1;45(3):1014-20. doi: 10.1021/es102425p. Epub 2010 Dec 21.
To obtain a systems-level understanding of Shewanella biology and ecology, the influence of electron acceptor availability on Shewanella's growth, metabolism, and transport needs to be elucidated. The diffusion gradient chamber (DGC) is an experimental tool developed to study population-level microbial growth and motility in response to concentration gradients. In this paper, the response of populations of Shewanella oneidensis MR-1 cells to an applied single gradient of the electron acceptor fumarate and applied opposing gradients of fumarate and nitrate, also an electron acceptor, were studied in the DGC. Mathematical models capable of predicting cellular growth and chemotaxis under the influence of gradients were used to analyze the results. Examining wild-type cells grown in a single gradient of fumarate, we found that MR-1 cells formed a chemotactic band that migrated up the electron acceptor gradient essentially as predicted by the model. The predicted velocity of the chemotactic cell band advancing toward the chemoattractant source (0.139 cm/h, R(2) = 0.996) closely matched that measured in the DGC (0.134 cm/h, R(2) = 0.997). Investigating the impact of opposing gradients of nitrate and fumarate on the chemotactic behaviors of S. oneidensis MR-1 fumarate reductase and nitrate reductase mutants, we found that the DGC was able to separate these mutants based upon their abilities to use the available electron acceptors in accordance with model predictions. Differences in the ability of Shewanella species to respond to and use available electron acceptors is thought to play an important role in their ecology. Therefore, these results validate the use of the DGC system to measure and simulate Shewanella chemotaxis in response to electron acceptor gradients and establish it as a research tool to help elucidate Shewanella's role in environmental processes.
为了从系统水平上理解希瓦氏菌的生物学和生态学，需要阐明电子受体可用性对希瓦氏菌生长、代谢和运输的影响。扩散梯度室（DGC）是一种实验工具，用于研究微生物种群在响应浓度梯度时的生长和运动。在本文中，我们使用 DGC 研究了 Shewanella oneidensis MR-1 细胞群体对施加的单一电子受体延胡索酸盐梯度以及施加的延胡索酸盐和硝酸盐（另一种电子受体）相反梯度的反应。使用能够预测梯度影响下细胞生长和趋化作用的数学模型来分析结果。在 DGC 中研究了在单一延胡索酸盐梯度中生长的野生型细胞，我们发现 MR-1 细胞形成了一个趋化带，基本上如模型所预测的那样沿着电子受体梯度迁移。向化学引诱剂源推进的趋化细胞带的预测速度（0.139 cm/h，R(2) = 0.996）与在 DGC 中测量的速度（0.134 cm/h，R(2) = 0.997）非常吻合。研究了硝酸盐和延胡索酸盐相反梯度对 S. oneidensis MR-1 延胡索酸盐还原酶和硝酸盐还原酶突变体趋化行为的影响，我们发现 DGC 能够根据可用电子受体的利用能力，按照模型预测将这些突变体分开。希瓦氏菌物种对可用电子受体的响应和利用能力的差异被认为在其生态学中起着重要作用。因此，这些结果验证了使用 DGC 系统测量和模拟希瓦氏菌对电子受体梯度的趋化反应，并将其确立为一种研究工具，有助于阐明希瓦氏菌在环境过程中的作用。
