Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido, Japan.
ISME J. 2013 Aug;7(8):1472-82. doi: 10.1038/ismej.2013.40. Epub 2013 Mar 14.
Anodic microbial communities in acetate-fed microbial fuel cells (MFCs) were analyzed using stable-isotope probing of 16S rRNA genes followed by denaturing gradient gel electrophoresis. The results revealed that Geobacter sulfurreducens and Hydrogenophaga sp. predominated in the anodic biofilm. Although the predominance of Geobacter sp. as acetoclastic exoelectrogens in acetate-fed MFC systems has been often reported, the ecophysiological role of Hydrogenophaga sp. is unknown. Therefore, we isolated and characterized a bacterium closely related to Hydrogenophaga sp. (designated strain AR20). The newly isolated strain AR20 could use molecular hydrogen (H2), but not acetate, with carbon electrode as the electron acceptor, indicating that the strain AR20 was a hydrogenotrophic exoelectrogen. This evidence raises a hypothesis that acetate was oxidized by G. sulfurreducens in syntrophic cooperation with the strain AR20 as a hydrogen-consuming partner in the acetate-fed MFC. To prove this hypothesis, G. sulfurreducens strain PCA was cocultivated with the strain AR20 in the acetate-fed MFC without any dissolved electron acceptors. In the coculture MFC of G. sulfurreducens and strain AR20, current generation and acetate degradation were the highest, and the growth of strain AR20 was observed. No current generation, acetate degradation and cell growth occurred in the strain AR20 pure culture MFC. These results show for the first time that G. sulfurreducens can oxidize acetate in syntrophic cooperation with the isolated Hydrogenophaga sp. strain AR20, with electrode as the electron acceptor.
采用稳定同位素探针技术（16S rRNA 基因）结合变性梯度凝胶电泳（DGGE）分析了乙酸盐喂养的微生物燃料电池（MFC）中的阳极微生物群落。结果表明，Geobacter sulfurreducens 和 Hydrogenophaga sp. 在阳极生物膜中占优势。虽然 Geobacter sp. 作为乙酸盐喂养 MFC 系统中的乙酸盐脱乙酰基好氧微生物经常被报道，但 Hydrogenophaga sp. 的生态生理学作用尚不清楚。因此，我们分离并鉴定了一种与 Hydrogenophaga sp. 密切相关的细菌（命名为菌株 AR20）。新分离的菌株 AR20 可以使用分子氢（H2），而不是乙酸盐，以碳电极作为电子受体，表明该菌株 AR20 是一种氢营养型好氧微生物。这一证据提出了一个假设，即乙酸盐由 Geobacter sulfurreducens 在与作为氢消耗伙伴的菌株 AR20 的共代谢协同作用下氧化，在乙酸盐喂养的 MFC 中。为了验证这一假设，我们将 G. sulfurreducens 菌株 PCA 与菌株 AR20 在没有任何溶解电子受体的乙酸盐喂养 MFC 中共培养。在 G. sulfurreducens 和菌株 AR20 的共培养 MFC 中，电流产生和乙酸盐降解最高，并且观察到菌株 AR20 的生长。在菌株 AR20 纯培养 MFC 中没有电流产生、乙酸盐降解和细胞生长。这些结果首次表明，Geobacter sulfurreducens 可以与分离的 Hydrogenophaga sp. 菌株 AR20 共代谢协同作用，以电极作为电子受体氧化乙酸盐。
