Center for Environmental Biotechnology, Biodesign Institute at Arizona State University, Tempe, Arizona 85287, USA.
Environ Sci Technol. 2009 Dec 15;43(24):9519-24. doi: 10.1021/es902165y.
Anode-respiring bacteria (ARB) are able to transfer electrons contained in organic substrates to a solid electrode. The selection of ARB should depend on the anode potential, which determines the amount of energy available for bacterial growth and maintenance. In our study, we investigated how anode potential affected the microbial diversity of the biofilm community. We used a microbial electrolysis cell (MEC) containing four graphite electrodes, each at a different anode potential (E(anode) = -0.15, -0.09, +0.02, and +0.37 V vs SHE). We used wastewater-activated sludge as inoculum, acetate as substrate, and continuous-flow operation. The two electrodes at the lowest potentials showed a faster biofilm growth and produced the highest current densities, reaching up to 10.3 A/m(2) at the saturation of an amperometric curve; the electrode at the highest potential produced a maximum of 0.6 A/m(2). At low anode potentials, clone libraries showed a strong selection (92-99% of total clones) of an ARB that is 97% similar to G. sulfurreducens. At the highest anode potential, the ARB community was diverse. Cyclic voltammograms performed on each electrode suggest that the ARB grown at the lowest potentials carried out extracellular electron transport exclusively by conducting electrons through the extracellular biofilm matrix. This is supported by scanning electron micrographs showing putative bacterial nanowires and copious EPS at the lowest potentials. Non-ARB and ARB using electron shuttles in the diverse community for the highest anode potential may have insulated the ARB using a solid conductive matrix from the anode. Continuous-flow operation and the selective pressure due to low anode potentials selected for G. sulfurreducens, which are known to consume acetate efficiently and use a solid conductive matrix for electron transport.
阳极呼吸细菌（ARB）能够将有机基质中含有的电子转移到固体电极上。ARB 的选择应取决于阳极电位，这决定了可供细菌生长和维持的能量。在我们的研究中，我们研究了阳极电位如何影响生物膜群落的微生物多样性。我们使用含有四个石墨电极的微生物电解池（MEC），每个电极的阳极电位（E（阳极）=-0.15、-0.09、+0.02 和+0.37 V 相对于 SHE）不同。我们使用废水活性污泥作为接种物，乙酸盐作为底物，并进行连续流动操作。两个电位最低的电极表现出更快的生物膜生长并产生最高的电流密度，在安培曲线的饱和时达到 10.3 A/m(2)；最高电位的电极产生的最大电流密度为 0.6 A/m(2)。在低阳极电位下，克隆文库显示出对一种 ARB 的强烈选择（总克隆的 92-99%），该 ARB 与 G. sulfurreducens 相似度为 97%。在最高阳极电位下，ARB 群落多样性较高。对每个电极进行的循环伏安法表明，在最低电位下生长的 ARB 仅通过在细胞外生物膜基质中传导电子来进行细胞外电子传输。这得到了在最低电位下显示出推测的细菌纳米线和丰富的 EPS 的扫描电子显微镜图像的支持。在最高阳极电位下，使用电子穿梭物的非 ARB 和 ARB 可能通过固体导电基质将 ARB 与阳极隔离开来。连续流动操作和由于低阳极电位而产生的选择性压力选择了 G. sulfurreducens，因为它已知能够有效地消耗乙酸盐并使用固体导电基质进行电子传输。
