PDF(Pubmed)
Abstract：
Direct interspecies electron transfer (DIET) may be most important in methanogenic environments, but mechanistic studies of DIET to date have primarily focused on cocultures in which fumarate was the terminal electron acceptor. To better understand DIET with methanogens, the transcriptome of Geobacter metallireducens during DIET-based growth with G. sulfurreducens reducing fumarate was compared with G. metallireducens grown in coculture with diverse Methanosarcina. The transcriptome of G. metallireducens cocultured with G. sulfurreducens was significantly different from those with Methanosarcina. Furthermore, the transcriptome of G. metallireducens grown with Methanosarcina barkeri, which lacks outer-surface c-type cytochromes, differed from those of G. metallireducens cocultured with M. acetivorans or M. subterranea, which have an outer-surface c-type cytochrome that serves as an electrical connect for DIET. Differences in G. metallireducens expression patterns for genes involved in extracellular electron transfer were particularly notable. Cocultures with c-type cytochrome deletion mutant strains, ∆Gmet_0930, ∆Gmet_0557 and ∆Gmet_2896, never became established with G. sulfurreducens but adapted to grow with all three Methanosarcina. Two porin-cytochrome complexes, PccF and PccG, were important for DIET; however, PccG was more important for growth with Methanosarcina. Unlike cocultures with G. sulfurreducens and M. acetivorans, electrically conductive pili were not needed for growth with M. barkeri. Shewanella oneidensis, another electroactive microbe with abundant outer-surface c-type cytochromes, did not grow via DIET. The results demonstrate that the presence of outer-surface c-type cytochromes does not necessarily confer the capacity for DIET and emphasize the impact of the electron-accepting partner on the physiology of the electron-donating DIET partner.
摘要：
在产甲烷环境中，直接的种间电子转移（DIET）可能是最重要的。但是迄今为止，对DIET的机理研究主要集中在以富马酸酯为末端电子受体的共培养上。为了更好地了解使用产甲烷菌的饮食，将还原富马酸G.硫还原菌在基于DIET的生长过程中的金属还原菌的转录组与在与多种甲烷共培养中生长的金属还原菌进行了比较。与硫还原G.共培养的金属还原G.的转录组与甲烷的转录组明显不同。此外，用甲烷弧菌生长的金属还原菌的转录组，缺乏外表面c型细胞色素，与与M.acetivorans或M.subterranea共培养的G.metallireducens不同，具有外表面c型细胞色素，可作为DIET的电连接。涉及细胞外电子转移的基因的金属还原G.与c型细胞色素缺失突变株共培养，△Gmet_0930、△Gmet_0557和△Gmet_2896从未与硫还原G.一起建立，但适应于与所有三种甲烷核菌一起生长。两种孔蛋白-细胞色素复合物，PccF和PccG，对饮食很重要；然而，PccG对甲烷藻的生长更为重要。与硫还原菌和M.acetivorans共培养不同，与M.barkeri一起生长不需要导电菌毛。Shewanellaoneidensis,另一种具有丰富外表面c型细胞色素的电活性微生物，没有通过饮食生长。结果表明，外表面c型细胞色素的存在并不一定赋予DIET的能力，并强调了电子接受伴侣对供电子DIET伴侣的生理学的影响。
