Veazey Joshua P, Reguera Gemma, Tessmer Stuart H
Department of Physics & Astronomy, Michigan State University, East Lansing, Michigan 48824-2320, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 Dec;84(6 Pt 1):060901. doi: 10.1103/PhysRevE.84.060901. Epub 2011 Dec 6.
The metal-reducing bacterium Geobacter sulfurreducens produces conductive protein appendages known as "pilus nanowires" to transfer electrons to metal oxides and to other cells. These processes can be harnessed for the bioremediation of toxic metals and the generation of electricity in bioelectrochemical cells. Key to these applications is a detailed understanding of how these nanostructures conduct electrons. However, to the best of our knowledge, their mechanism of electron transport is not known. We used the capability of scanning tunneling microscopy (STM) to probe conductive materials with higher spatial resolution than other scanning probe methods to gain insights into the transversal electronic behavior of native, cell-anchored pili. Despite the presence of insulating cellular components, the STM topography resolved electronic molecular substructures with periodicities similar to those reported for the pilus shaft. STM spectroscopy revealed electronic states near the Fermi level, consistent with a conducting material, but did not reveal electronic states expected for cytochromes. Furthermore, the transversal conductance was asymmetric, as previously reported for assemblies of helical peptides. Our results thus indicate that the Geobacter pilus shaft has an intrinsic electronic structure that could play a role in charge transport.
金属还原菌硫还原地杆菌会产生被称为“菌毛纳米线”的导电蛋白附属物，用于将电子转移至金属氧化物以及其他细胞。这些过程可用于有毒金属的生物修复以及生物电化学电池中的发电。这些应用的关键在于详细了解这些纳米结构是如何传导电子的。然而，据我们所知，它们的电子传输机制尚不清楚。我们利用扫描隧道显微镜（STM）比其他扫描探针方法更高的空间分辨率来探测导电材料的能力，以深入了解天然的、细胞锚定菌毛的横向电子行为。尽管存在绝缘的细胞成分，但STM形貌解析出了具有与菌毛轴报道的周期性相似的电子分子亚结构。STM光谱揭示了费米能级附近的电子态，这与导电材料一致，但未揭示细胞色素预期的电子态。此外，横向电导是不对称的，这与之前报道的螺旋肽组装情况相同。因此，我们的结果表明，硫还原地杆菌的菌毛轴具有一种内在的电子结构，可能在电荷传输中发挥作用。
