科学网—导电细菌鞭毛蛋白电子传递链所必需的氨基酸

微生物燃料电池（MFCs）可以借助微生物的催化作用直接将燃料(如有机酸,糖类等)的化学能转化为电能。某些类型的细菌具有将电子传递到细胞外并与外界电子受体接合的能力,可以用于构建微生物燃料电池.微生物燃料电池的研究集中于产电细菌、电极材料和电池反应器构型等方面,同时,微生物燃料电池在废水处理、生物修复等方面具有广阔的应用前景（杨敬东等，2010）。

图片来源：Logan et al. 2006. http://pubs./doi/pdf/10.1021/es0605016 

最近，来自Massachusetts大学的Lovley等研究者，发现导电细菌Geobacter sulfurreducens鞭毛（pili）能够导电的核心氨基酸。细菌鞭毛主要由3部分组成：中央轴纤丝、围绕它的质膜和一些细胞质，犹如铜丝电线。中央轴纤丝是由蛋白质所组成的,就如电线里的铜丝。Lovley等改造了Geobacter sulfurreducens纤丝蛋白中位于C末端的氨基酸序列（该末端的氨基酸序列差异被认为是导致Geobacter sulfurreducens不同菌株导电性差异的重要功能域），用丙氨酸代替了野生型中5个芳香族氨基酸，该工程菌株命名为Aro-5。研究发现，与野生型相比，Aro-5形态结构没有差别，但对培养基内的3价铁离子（Fe（III））还原成2价离子（Fe(II)）的能力降低，证明Aro-5传递电子的能力降低。该研究结果表明Geobacter sulfurreducens鞭毛蛋白中的芳香族氨基酸对电子长距离体外传递的重要性。

原文链接：Aromatic amino acids required for pili conductivity and long-range extracellular electron transport in Geobacter sulfurreducens. mBio 4(2):e00105-13. doi:10.1128/mBio.00105-13.

http://mbio./content/4/2/e00105-13

Abstract

It has been proposed that Geobacter sulfurreducens requires conductive pili for long-range electron transport to Fe(III) oxides and for high-density current production in microbial fuel cells. In order to investigate this further, we constructed a strain of G. sulfurreducens, designated Aro-5, which produced pili with diminished conductivity. This was accomplished by modifying the amino acid sequence of PilA, the structural pilin protein. An alanine was substituted for each of the five aromatic amino acids in the carboxyl terminus of PilA, the region in which G. sulfurreducens PilA differs most significantly from the PilAs of microorganisms incapable of long-range extracellular electron transport. Strain Aro-5 produced pili that were properly decorated with the multiheme c-type cytochrome OmcS, which is essential for Fe(III) oxide reduction. However, pili preparations of the Aro-5 strain had greatly diminished conductivity and Aro-5 cultures were severely limited in their capacity to reduce Fe(III) compared to the control strain. Current production of the Aro-5 strain, with a graphite anode serving as the electron acceptor, was less than 10% of that of the control strain. The conductivity of the Aro-5 biofilms was 10-fold lower than the control strain’s. These results demonstrate that the pili of G. sulfurreducens must be conductive in order for the cells to be effective in extracellular long-range electron transport.

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