UHasselt-X-LAB, Agoralaan, 3590 Diepenbeek, Belgium.
Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.
Anal Chem. 2021 May 18;93(19):7226-7234. doi: 10.1021/acs.analchem.1c00298. Epub 2021 May 3.
Cable bacteria are electroactive bacteria that form a long, linear chain of ridged cylindrical cells. These filamentous bacteria conduct centimeter-scale long-range electron transport through parallel, interconnected conductive pathways of which the detailed chemical and electrical properties are still unclear. Here, we combine time-of-flight secondary-ion mass spectrometry (ToF-SIMS) and atomic force microscopy (AFM) to investigate the structure and composition of this naturally occurring electrical network. The enhanced lateral resolution achieved allows differentiation between the cell body and the cell-cell junctions that contain a conspicuous cartwheel structure. Three ToF-SIMS modes were compared in the study of so-called fiber sheaths (i.e., the cell material that remains after the removal of cytoplasm and membranes, and which embeds the electrical network). Among these, fast imaging delayed extraction (FI-DE) was found to balance lateral and mass resolution, thus yielding the following multiple benefits in the study of structure-composition relations in cable bacteria: (i) it enables the separate study of the cell body and cell-cell junctions; (ii) by combining FI-DE with in situ AFM, the depth of Ni-containing protein-key in the electrical transport-is determined with greater precision; and (iii) this combination prevents contamination, which is possible when using an ex situ AFM. Our results imply that the interconnects in extracted fiber sheaths are either damaged during extraction, or that their composition is different from fibers, or both. From a more general analytical perspective, the proposed methodology of ToF-SIMS in the FI-DE mode combined with in situ AFM holds great promise for studying the chemical structure of other biological systems.
电缆菌是一种具有电活性的细菌，它由长而线性的脊状圆柱形细胞组成。这些丝状细菌通过平行的、相互连接的导电途径进行厘米级的长程电子传输，而这些途径的详细化学和电学性质仍不清楚。在这里，我们结合飞行时间二次离子质谱（ToF-SIMS）和原子力显微镜（AFM）来研究这个自然存在的电网络的结构和组成。增强的横向分辨率允许我们区分细胞体和包含明显的轮辐结构的细胞-细胞连接处。在研究所谓的纤维鞘（即细胞质和细胞膜去除后留下的包含电网络的细胞物质）时，比较了三种 ToF-SIMS 模式。其中，快速成像延迟提取（FI-DE）模式在平衡横向和质量分辨率方面表现出色，从而在电缆菌的结构-组成关系研究中带来了以下多个好处：（i）它能够分别研究细胞体和细胞-细胞连接处；（ii）通过将 FI-DE 与原位 AFM 相结合，可以更精确地确定在电传输中起关键作用的含 Ni 蛋白质的深度；（iii）这种组合可以防止污染，而原位 AFM 可能会导致污染。我们的结果表明，提取的纤维鞘中的互连在提取过程中要么受损，要么其组成与纤维不同，或者两者兼而有之。从更广泛的分析角度来看，所提出的 FI-DE 模式下的 ToF-SIMS 与原位 AFM 相结合的方法为研究其他生物系统的化学结构提供了很大的前景。
