Biofilm Biology and Engineering of Geobacter and Shewanella spp. for Energy Applications

Abstract

Geobacter and Shewanella spp. were discovered in late 1980s as dissimilatory metal-reducing microorganisms that can transfer electrons from cytoplasmic respiratory oxidation reactions to external metal-containing minerals. In addition to mineral-based electron acceptors, Geobacter and Shewanella spp. also can transfer electrons to electrodes. The microorganisms that have abilities to transfer electrons to electrodes are known as exoelectrogens. Because of their remarkable abilities of electron transfer, Geobacter and Shewanella spp. have been the two most well studied groups of exoelectrogens. They are widely used in bioelectrochemical systems (BESs) for various biotechnological applications, such as bioelectricity generation via microbial fuel cells. These applications mostly associate with Geobacter and Shewanella biofilms grown on the surfaces of electrodes. Geobacter and Shewanella biofilms are electrically conductive, which is conferred by matrix-associated electroactive components such as c-type cytochromes and electrically conductive nanowires. The thickness and electroactivity of Geobacter and Shewanella biofilms have a significant impact on electron transfer efficiency in BESs. In this review, we first briefly discuss the roles of planktonic and biofilm-forming Geobacter and Shewanella cells in BESs, and then review biofilm biology with the focus on biofilm development, biofilm matrix, heterogeneity in biofilm and signaling regulatory systems mediating formation of Geobacter and Shewanella biofilms. Finally, we discuss strategies of Geobacter and Shewanella biofilm engineering for improving electron transfer efficiency to obtain enhanced BES performance.

Enhancing electrical outputs of the fuel cells with Geobacter sulferreducens by overexpressing nanowire proteins

“…On the other hand, Geobacter pili may mediate the secretion of OmcS and OmcZ (Gu et al, 2021 ). In addition to their electron transfer roles, cytochromes may act as important structural components in biofilm matrix (Hu et al, 2021 ). Similarly, the results of this investigation also indicated the structural roles of OmcZ, OmcS and OmcT in biofilm formation.…”

“…For example, G. sulfurreducens generates the highest current density of wild‐type microbes available in pure culture (Nevin et al, 2008 ; Rotaru et al, 2015 ; Yi et al, 2009 ). The electrical output of MFCs is significantly impacted by the thickness and conductivity of G. sulfurreducens biofilm grown on the surfaces of electrodes (Hu et al, 2021 ; Malvankar et al, 2012 ; Reguera et al, 2006 ; Steidl et al, 2016 ). Generally, thick biofilms with high conductivity are expected to generate high current density.…”

Polyaniline-Derived Nitrogen-Containing Carbon Nanostructures with Different Morphologies as Anode Modifier in Microbial Fuel Cells

“…At the genus and family levels ( Figure 6 ), results show multiple taxa with high relative abundance, which are frequently associated with the ability for extracellular electron transfer (EET). The Geobacter genus, the type genus studied for its exoelectrogenic capabilities [ 61 , 62 ], had a relative abundance more than twofold greater in the case of the PANI-T-900-modified CC anode (6.62%) than the PANI-R-900-modified CC anode (3.05%), representing a possible justification for its better power generation. Furthermore, Thermoanaerobacter sp.…”

Electrogenic Bacteria Promise New Opportunities for Powering, Sensing, and Synthesizing

“…[173,174] Electrogenic bacteria are known for their extraordinary capability to electrochemically interact with external redox-active materials, which could promote seamless contact between biological systems and external electronics. Conventionally, such living electrodes are obtained by natural biofilm formation, [171,175,176] increasing the surface-area-to-volume ratio of the electrode, [20,[177][178][179][180] or modifying the electrode surface free energy to favor bacterial attachment. [174,181] More recently, the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) gained considerable attention in the field of bioelectronics because of its biocompatibility, good electric and ionic conductivity, and chemical stability.…”