Tactic Response of Shewanella oneidensis MR-1 toward Insoluble Electron Acceptors
Tactic Response of Shewanella oneidensis MR-1 toward Insoluble Electron Acceptors
复制标题
Shewanella oneidensis MR-1 对不溶性电子受体的策略反应
作者：
Oram J
外生电生细菌的定义是其对胞外和不溶性电子受体的呼吸能力，在生物修复和微生物电化学系统(MESS)中具有应用，同时在生物地球化学循环中发挥重要作用。圆锥希瓦氏菌MR-1已成为研究细胞外呼吸作用的模式生物，它对包括电极在内的不溶性电子受体具有趋向性。对于MR-1的S策略行为，已经提出了多种机制，在这里，我们报道了在三电极电化学池中通过视频显微镜细胞跟踪实验来研究电化学势的作用。用粒子跟踪算法确定了MR-1的轨迹，并用香农的熵方法进行了验证。观察到MR-1在电化学池中的策略响应依赖于施加的电位，如靠近电极(<；50 µm)的移动(>；4 /S)MR-1的平均速度和密度。在氧化电位下观察到了策略行为，在−0.15~−0.25 V与标准氢电极(SHE)之间有很强的切换，这与黄素的还原电位一致。当加入核黄素(2 µM)时，靠近电极的运动MR-1的平均速度和密度增加，但在MR-1的ΔmtrC/ΔomcA突变体中完全不存在。除了黄素作为电子媒介支持不溶性电子受体上的厌氧呼吸外，我们还提出核黄素是由MR-1分泌出来的，以感知其环境中的氧化还原梯度，帮助趋向性不溶性电子受体，包括MES中的电极。重要信息以前关于外生电生细菌策略行为的假设基于不能准确控制电化学电位的技术，例如化学插塞分析或双电极细胞中的显微镜跟踪实验。在这里，我们回顾了以前的实验，并首次在三电极电化学池中进行了显微细胞跟踪实验，确定了电极电位。在这些实验的基础上，观察到向电极的趋向性在−0.2 V左右切换到标准氢电极(SHE)，这与黄素的还原电位一致。
Exoelectrogenic bacteria are defined by their ability to respire on extracellular and insoluble electron acceptors and have applications in bioremediation and microbial electrochemical systems (MESs), while playing important roles in biogeochemical cycling. Shewanella oneidensis MR-1, which has become a model organism for the study of extracellular respiration, is known to display taxis toward insoluble electron acceptors, including electrodes. Multiple mechanisms have been proposed for MR-1’s tactic behavior, and, here, we report on the role of electrochemical potential by video microscopy cell tracking experiments in three-electrode electrochemical cells. MR-1 trajectories were determined using a particle tracking algorithm and validated with Shannon’s entropy method. Tactic response by MR-1 in the electrochemical cell was observed to depend on the applied potential, as indicated by the average velocity and density of motile (>4 µm/s) MR-1 close to the electrode (<50 µm). Tactic behavior was observed at oxidative potentials, with a strong switch between the potentials −0.15 to −0.25 V versus the standard hydrogen electrode (SHE), which coincides with the reduction potential of flavins. The average velocity and density of motile MR-1 close to the electrode increased when riboflavin was added (2 µM), but were completely absent in a ΔmtrC/ΔomcAmutant of MR-1. Besides flavin’s function as an electron mediator to support anaerobic respiration on insoluble electron acceptors, we propose that riboflavin is excreted by MR-1 to sense redox gradients in its environment, aiding taxis toward insoluble electron acceptors, including electrodes in MESs.IMPORTANCEPrevious hypotheses of tactic behavior of exoelectrogenic bacteria are based on techniques that do not accurately control the electrochemical potential, such as chemical-in-plug assays or microscopy tracking experiments in two-electrode cells. Here, we have revisited previous experiments and, for the first time, performed microscopy cell-tracking experiments in three-electrode electrochemical cells, with defined electrode potentials. Based on these experiments, taxis toward electrodes is observed to switch at about −0.2 V versus standard hydrogen electrode (SHE), coinciding with the reduction potential of flavins.
影响因子：
6.6
作者：
Xu, Shuai;Jangir, Yamini;El-Naggar, Mohamed Y.
通讯作者：
El-Naggar, Mohamed Y.
用于确定和评估细菌群体趋化反应的视频处理分析。
影响因子：
2.2
作者：
Melina Nisenbaum;E. Maldonado;J. Martínez Arca;J. González;L. Passoni;S. Murialdo
通讯作者：
S. Murialdo