Reguera Gemma, McCarthy Kevin D, Mehta Teena, Nicoll Julie S, Tuominen Mark T, Lovley Derek R
Department of Microbiology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Nature. 2005 Jun 23;435(7045):1098-101. doi: 10.1038/nature03661.
Microbes that can transfer electrons to extracellular electron acceptors, such as Fe(iii) oxides, are important in organic matter degradation and nutrient cycling in soils and sediments. Previous investigations on electron transfer to Fe(iii) have focused on the role of outer-membrane c-type cytochromes. However, some Fe(iii) reducers lack c-cytochromes. Geobacter species, which are the predominant Fe(iii) reducers in many environments, must directly contact Fe(iii) oxides to reduce them, and produce monolateral pili that were proposed, on the basis of the role of pili in other organisms, to aid in establishing contact with the Fe(iii) oxides. Here we report that a pilus-deficient mutant of Geobacter sulfurreducens could not reduce Fe(iii) oxides but could attach to them. Conducting-probe atomic force microscopy revealed that the pili were highly conductive. These results indicate that the pili of G. sulfurreducens might serve as biological nanowires, transferring electrons from the cell surface to the surface of Fe(iii) oxides. Electron transfer through pili indicates possibilities for other unique cell-surface and cell-cell interactions, and for bioengineering of novel conductive materials.
能够将电子传递给细胞外电子受体（如三价铁氧化物）的微生物，在土壤和沉积物中的有机物降解及养分循环过程中发挥着重要作用。先前关于电子向三价铁传递的研究主要集中在外膜c型细胞色素的作用上。然而，一些三价铁还原菌缺乏c型细胞色素。地杆菌属细菌是许多环境中主要的三价铁还原菌，它们必须直接接触三价铁氧化物才能将其还原，并产生单侧菌毛。基于菌毛在其他生物中的作用，推测这些菌毛有助于与三价铁氧化物建立接触。在此，我们报道了一株硫还原地杆菌菌毛缺陷型突变体，它无法还原三价铁氧化物，但能够附着在上面。导电探针原子力显微镜显示，这些菌毛具有高导电性。这些结果表明，硫还原地杆菌的菌毛可能充当生物纳米线，将电子从细胞表面传递到三价铁氧化物表面。通过菌毛进行电子传递意味着其他独特的细胞表面和细胞间相互作用以及新型导电材料生物工程的可能性。
