Geobacter Electrochemically Deposited on a Gold Substrate

The electrogenic bacterium Geobacter sulfurreducens has the potential to oxidize organic compounds and move the released electrons to a conductive substrate. There is extensive research surrounding electrogenic bacteria, in order to develop microbial fuel cells that oxidize organic compounds to generate electric energy.

These microbial fuel cells are believed to produce electricity by oxidizing organic contaminations - for example, those found in communal waste waters. Out of all the pure cultures in this process the highest current density was demonstrated by G. sulfurreducens.

Growth of Biofilm

A better understanding of the bacterial adsorption process on conductive substrates, the eventual divison of the substrates, and the formation of a biofilm is necessary in order to develop microbial fuel cells. The biofilm is a complex structure that is formed by numerous layers of bacterial cells, and is microscopically thick.

The chemical composition and morphology of the substrate strongly influence the development of the biofilm, right from the adherence of the first bacteria. Research on the growth of biofilm on electrodes that are modified using a variety of functionalized monolayers are of special interest.

AFM Imaging of Bacteria

AFM can be used to visualize the morphology of the substrate as well as the bacteria on monolayer-modified or bare substrates, from the initial bacterial cells attached. Unlike scanning electron microscopy and other such microscopic methods, AFM does not involve gold sputtering and glutaraldehyde fixing treatments that kill the examined bacteria.

The evolution of biofilm can be observed through a single sample using AFM. In addition, online observation of bacteria adhesion, division, and development of the biofilm can be obtained from in situ AFM imaging of bacteria.

Figure 1 demonstrates an AFM image of G. sulfurreducens that has been electrochemically deposited on a gold substrate. The image, captured by a Nanosurf FlexAFM, shows the untreated specimen in ambient air, after it was removed from the solution and left to dry.

Bacterial cells adhered above other bacteria are also visible, in addition to individual bacteria and bacteria groups that have been directly absorbed on the gold surface. The former indicates the initial step in the formation of bacterial biofilm.

Dynamic mode AFM image of untreated electrogenic bacteria Geobacter sulfurreducens electrochemically deposited on gold substrate. Image processing: SPIP.

Figure 1. Dynamic mode AFM image of untreated electrogenic bacteria Geobacter sulfurreducens electrochemically deposited on gold substrate. Image processing: SPIP.

This information has been sourced, reviewed and adapted from materials provided by Nanosurf AG.

For more information on this source, please visit Nanosurf AG.

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