Surface multiheme c-type cytochromes from Thermincola potens and implications for respiratory metal reduction by Gram- positive bacteria
Surface multiheme c-type cytochromes from Thermincola potens and implications for respiratory metal reduction by Gram- positive bacteria
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DOI：
10.1073/pnas.1112905109
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发表时间：
2012-01-31
影响因子：
11.1
通讯作者：
Coates, John D.
中科院分区：
文献类型：
--
作者：
Carlson, Hans K.;Iavarone, Anthony T.;Coates, John D.
尽管革兰氏阳性菌可能是某些环境中的优势菌，但它们对金属的异化还原机制几乎一无所知。从接种厌氧消化器污泥并在55摄氏度下运行的微生物燃料电池的阳极中分离出嗜热菌JR菌株。初步鉴定表明，T.电位耦合乙酸氧化还原水合氧化铁（HFO）或蒽醌-2，6二磺酸盐（AQDS），腐殖物质的氧化还原活性成分的类似物。T. potens的基因最近被测序，并且多血红素C型细胞色素（MHC）的丰度对于革兰氏阳性细菌是不寻常的。我们目前的证据，从胰蛋白酶剃须LC-MS/MS实验和表面增强拉曼光谱（Sers），表明在T。MHCs在HFO或AQDS上具有潜在的生长潜力，并且几种MHCs定位于细胞壁或细胞表面。此外，其中一种MHC可以从具有低pH或变性剂的细胞中提取，表明与细胞壁或细胞表面的松散缔合。电子显微镜没有显示S-层，和沉淀的银金属在细胞表面上被抑制氰化物，支持参与表面局部氧化还原活性血红素蛋白质的异化金属还原。这些结果为细胞壁相关的细胞色素提供了独特的直接证据，并支持MHC参与传导电子穿过革兰氏阳性细菌的细胞被膜。
Almost nothing is known about the mechanisms of dissimilatory metal reduction byGram-positive bacteria, although theymay be the dominant species in some environments. Thermincola potens strain JR was isolated from the anode of a microbial fuel cell inoculated with anaerobic digester sludge and operated at 55 degrees C. Preliminary characterization revealed that T. potens coupled acetate oxidation to the reduction of hydrous ferric oxides (HFO) or anthraquinone-2,6disulfonate (AQDS), an analog of the redox active components of humic substances. The genome of T. potens was recently sequenced, and the abundance of multiheme c-type cytochromes (MHCs) is unusual for a Gram-positive bacterium. We present evidence from trypsin-shaving LC-MS/MS experiments and surface-enhanced Raman spectroscopy (SERS) that indicates the expression of a number of MHCs during T. potens growth on either HFO or AQDS, and that several MHCs are localized to the cell wall or cell surface. Furthermore, one of the MHCs can be extracted from cells with low pH or denaturants, suggesting a loose association with the cell wall or cell surface. Electron microscopy does not reveal an S-layer, and the precipitation of silver metal on the cell surface is inhibited by cyanide, supporting the involvement of surface-localized redox-active heme proteins in dissimilatory metal reduction. These results provide unique direct evidence for cell wall-associated cytochromes and support MHC involvement in conducting electrons across the cell envelope of a Gram-positive bacterium.