Probing single- to multi-cell level charge transport in Geobacter sulfurreducens DL-1

Abstract

Microbial fuel cells, in which living microorganisms convert chemical energy into electricity, represent a potentially sustainable energy technology for the future. Here we report the single-bacterium level current measurements of Geobacter sulfurreducens DL-1 to elucidate the fundamental limits and factors determining maximum power output from a microbial fuel cell. Quantized stepwise current outputs of 92(±33) and 196(±20) fA are generated from microelectrode arrays confined in isolated wells. Simultaneous cell imaging/tracking and current recording reveals that the current steps are directly correlated with the contact of one or two cells with the electrodes. This work establishes the amount of current generated by an individual Geobacter cell in the absence of a biofilm and highlights the potential upper limit of microbial fuel cell performance for Geobacter in thin biofilms.

A combined electrochemical and optical trapping platform for measuring single cell respiration rates at electrode interfaces

“…Our observation that only a fraction of the cells is actively respiring at electrodes is consistent with a previous study not based on optical trapping. 26 It remains unclear whether such a percentage of actively electroderespiring cells reflects the typical heterogeneity in these cultures, or whether it stems from the particular growth procedure used in this and previous studies; our finding clearly motivates additional single cell studies of the statistical distribution in EET as a function of various growth conditions. In comparison, no EET current was detected from any of 20 ∆OMC cells tested under identical conditions, further validating our measurement system, as the outer membrane multiheme cytochromes are known to be necessary for mediating EET.…”

“…Another study obtained single cell measurements of EET from a different DMRB, Geobacter sulfurreducens DL-1, using microscale Ti/Au electrode arrays. 26 When active cells transiently came into contact with these electrodes, a short circuit current of 92(±33) fA per cell was observed in about 30% of the contact events. Finally, Liu et al reported an innovative approach taking advantage of optical tweezers to attach single S. oneidensis MR-1 cells to electrodes, revealing a current output of 200 fA per cell at a working electrode potential of +200 mV vs. Ag/AgCl.…”

Zooming in to see the bigger picture: Microfluidic and nanofabrication tools to study bacteria

“…Experiments on Geobacter sulfurreducens suggested that it uses a different mechanism to transport electrons (6). Simultaneous imaging and current detection of single G. sulfurreducens in contact with a nanofabricated electrode is shown in Fig.…”

What Is the Essence of Microbial Electroactivity?

“…In this case, the coulombic efficiency might seem a good objective measure of electroactivity being independent of cell number and also considering potential electron losses within the cell. Experimentally, even harder to determine would be the electron transfer per single cell (Liu et al, 2010; Jiang et al, 2013; Gross and El-Naggar, 2015), which from our perspective could be considered an excellent measure. On the technical scale, biomass respective number of cells, N cell , or formed product, P , is often in focus.…”