Improving charge collection in Escherichia coli–carbon electrode devices with conjugated oligoelectrolytes

Abstract

It is important to tailor biotic-abiotic interfaces in order to maximize the utility of bioelectronic devices such as microbial fuel cells (MFCs), electrochemical sensors and bioelectrosynthetic systems. The efficiency of electron-equivalent extraction (or injection) across such biotic-abiotic interfaces is dependent on the choice of the microbe and the conductive electrode material. In this contribution, we show that spontaneous intercalation of a conjugated oligoelectrolyte, namely 4,4'-bis(4'-(N,N-bis(6''-(N,N,N-trimethylammonium)hexyl)amino)-styryl)stilbene tetraiodide (DSSN+), into the membranes of Escherichia coli leads to an increase in current generation in MFCs containing carbon-based electrodes. A combination of scanning electron microscopy (SEM) and confocal microscopy was employed to confirm the incorporation of DSSN+ into the cell membrane and biofilm formation atop carbon felt electrodes. Current collection was enhanced by more than 300% with addition of this conjugated oligoelectrolyte. The effect of DSSN+ concentration on electrical output was also investigated. Higher concentrations, up to 25 μM, lead to an overall increase in the number of charge equivalents transferred to the charge-collecting electrode, providing evidence in support of the central role of the synthetic system in improving device performance.

Membrane permeabilization by conjugated oligoelectrolytes accelerates whole-cell catalysis

“…21,27 In contrast to previous reports, the IM remains primarily intact under our experimental conditions. 9 Since the conditions described herein closely mimic that used in MFCs, it is unlikely that the increased extracellular electron transfer (EET) in MFCs is due to cell lysis.…”

Oligopolyphenylenevinylene-Conjugated Oligoelectrolyte Membrane Insertion Molecules Selectively Disrupt Cell Envelopes of Gram-Positive Bacteria

“…DSSNϩ, 1,4-bis(4Љ-(N,N-bis(6ЉЉ-(N,N,N-trimethylammonium)hexyl)amino)-styryl)benzene tetraiodide (DSBNϩ), and 1,4-bis(4Љ-(N,N-bis(6ЉЉ-(N,N,N-trimethylammonium)hexyl)amino)-styryl)-2,3,5,6 tetrafluorobenzene tetraiodide (4F-DSBNϩ) were synthesized as reported previously (2,11). The MIMs used in this study were selected because their biotechnological potential had been demonstrated previously in bioelectrochemical systems and because interesting interactions with microbial cells have been documented (1,3,10).…”

“…E. coli K-12 cells were incubated for 15 min in the dark with 5 and 64 M DSSNϩ, 5 M DSBNϩ, and 5 M 4F-DSBNϩ, while E. faecalis cells were treated with 1 M (each) DSSNϩ, DSBN, and 4F-DSBNϩ in the dark for 15 min. Treatment concentrations were selected to be close to but not above their corresponding MIC values (Table 2), with the exception of DSSNϩ, where values were selected to correspond to biotechnologically useful concentrations (1) and to be close to the MIC of DSSNϩ in E. coli, enabling the comparison of the toxic effects of all MIMs in both E. coli K-12 and E. faecalis using TEM. Following MIM treatment, cells were washed twice with PBS and resuspended to a final OD 600 of 1.…”

“…In this contribution, we examine the response of selected Gram-negative and Gram-positive organisms to three OPV-COE MIMs that have been the focus of previous studies (1,3,9,10). Furthermore, using a combination of specific deletion mutants along with a model membrane system, we will explore interactions between OPV-COEs and different components of the cellular envelope.…”

“…ligopolyphenylenevinylene-conjugated oligoelectrolytes (OPVCOEs) are a recently described class of membrane insertion molecules (MIMs) that target the microbial envelope with the specific aim of promoting charge transfer across microbial membranes and which potentially have a range of other biotechnological applications (1,2). OPV-COEs are amphipathic molecules consisting of a conjugated benzene ring backbone that is terminated with ionic pendant chains that have an affinity for biological membranes because of the charge distribution and amphiphilic nature of the molecule (see Fig.…”