Electrical transport along bacterial nanowires from Shewanella oneidensis MR-1

Abstract

Bacterial nanowires are extracellular appendages that have been suggested as pathways for electron transport in phylogenetically diverse microorganisms, including dissimilatory metal-reducing bacteria and photosynthetic cyanobacteria. However, there has been no evidence presented to demonstrate electron transport along the length of bacterial nanowires. Here we report electron transport measurements along individually addressed bacterial nanowires derived from electron-acceptor–limited cultures of the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1. Transport along the bacterial nanowires was independently evaluated by two techniques: ( i ) nanofabricated electrodes patterned on top of individual nanowires, and ( ii ) conducting probe atomic force microscopy at various points along a single nanowire bridging a metallic electrode and the conductive atomic force microscopy tip. The S. oneidensis MR-1 nanowires were found to be electrically conductive along micrometer-length scales with electron transport rates up to 10 9 /s at 100 mV of applied bias and a measured resistivity on the order of 1 Ω·cm. Mutants deficient in genes for c -type decaheme cytochromes MtrC and OmcA produce appendages that are morphologically consistent with bacterial nanowires, but were found to be nonconductive. The measurements reported here allow for bacterial nanowires to serve as a viable microbial strategy for extracellular electron transport.

Harnessing the power of microbial nanowires

“…The model representative Shewanella oneidensis MR‐1 was also assumed to produce pilus ‘nanowires’ (Gorby et al ., 2006; El‐Naggar et al ., 2010), although MR‐1 T4P had previously been shown to be nonconductive (Reguera et al ., 2005). These ‘nanowires’ were later found to be dehydrated forms of outer membrane extensions, which this bacterium forms by fusing outer membrane vesicles (Pirbadian et al ., 2014).…”

Genome-Facilitated Analyses of Geomicrobial Processes

“…This has led to a major effort by many others to understand the physical nature of the conductivity and the role of these structures in EET (11,20,21).…”

Influence of hydrogen-oxidizing bacteria on the corrosion of low carbon steel: Local electrochemical investigations

“…It is a facultative anaerobic bacterium [9] able to use different compounds as electron donor, such as lactate, formate, pyruvate, amino acids and also dihydrogen [10]. According to El-Naggar et al [11] the respiration rate of Shewanella oneidensis strain MR-1 is 2.6x10 6 electrons per cell per second using lactate as electron donor. In addition, some mechanisms of IRB species using electron transfers from solid substrates have already been described in the literature, such as:  the use of mediators which can act as electron shuttles transferring electrons from the cells to the acceptors compounds [12,13];  the direct contact of cells with solid substrate through multihemes cytochromes at the external membrane [14];  the use of conductive intracellular filaments (i.e.…”

“…In addition, some mechanisms of IRB species using electron transfers from solid substrates have already been described in the literature, such as:  the use of mediators which can act as electron shuttles transferring electrons from the cells to the acceptors compounds [12,13];  the direct contact of cells with solid substrate through multihemes cytochromes at the external membrane [14];  the use of conductive intracellular filaments (i.e. nanowires) [11]. It is well-known that the presence of microorganisms can influence the corrosion rate [6,[15][16][17][18][19], but is not well elucidated if IRB are able to induce local corrosion.…”