Interaction studies between periplasmic cytochromes provide insights into extracellular electron transfer pathways ofGeobacter sulfurreducens

Abstract

bacteria usually prevail among other microorganisms in soils and sediments where Fe(III) reduction has a central role. This reduction is achieved by extracellular electron transfer (EET), where the electrons are exported from the interior of the cell to the surrounding environment. Periplasmic cytochromes play an important role in establishing an interface between inner and outer membrane electron transfer components. In addition, periplasmic cytochromes, in particular nanowire cytochromes that contain at least 12 haem groups, have been proposed to play a role in electron storage in conditions of an environmental lack of electron acceptors. Up to date, no redox partners have been identified in , and concomitantly, the EET and electron storage mechanisms remain unclear. In this work, NMR chemical shift perturbation measurements were used to probe for an interaction between the most abundant periplasmic cytochrome PpcA and the dodecahaem cytochrome GSU1996, one of the proposed nanowire cytochromes in The perturbations on the haem methyl signals of GSU1996 and PpcA showed that the proteins form a transient redox complex in an interface that involves haem groups from two different domains located at the C-terminal of GSU1996. Overall, the present study provides for the first time a clear evidence for an interaction between periplasmic cytochromes that might be relevant for the EET and electron storage pathways in .

Potential regulates metabolism and extracellular respiration of electroactive Geobacter biofilm

“…Periplasmic and transmembrane electron relays are more diverse in species. Five proteins of the PpcA family and GSU1996 in periplasm are found to shuttle electrons from the cytoplasmic cyt c to downstream cyt clusters in the envelope (Dantas et al, ; Fernandes, Nunes, Paquete, & Salgueiro, ). Transmembrane electron flow across the envelope relies on cyt clusters such as OmaB–OmcB, OmaC–OmcC, extA–extC/D, and extG–extF, each of which is integrated with a porin for protein localization (Otero, Chan, & Bond, ; Shi et al, ).…”

“…Periplasmic and transmembrane electron relays are more diverse in species. Five proteins of the PpcA family and GSU1996 in periplasm are found to shuttle electrons from the cytoplasmic cyt c to downstream cyt clusters in the envelope Fernandes, Nunes, Paquete, & Salgueiro, 2017).…”

Electron Storage in Electroactive Biofilms

“…Several studies have focused on elucidating the role of c-type cytochromes in electron transport and storage. Esteve-Núñez and coworkers developed a fluorescence technique to measure the redox status of c-type cytochromes to evaluate their capacity [37], while Fernandes and coworkers used NMR to study periplasmic cytochromes [38]. Capacitance and storage in redox components of EABs on cathodes has, to the best of our knowledge, not been studied.…”

Metal Nanoparticle–Microbe Interactions: Synthesis and Antimicrobial Effects

“…Several different types of c‐type cytochromes are at play: Some can act as electron carriers in the outer membrane with, e.g., 12 heme units, while others are smaller, e.g., with three heme units, acting as electron shuttles in the periplasm. Yet, the exact interplay between them [ 145 ] and electron flow within each cytochrome [ 146 ] is still under investigation. It has also been reported that small monoheme c‐type cytochromes are excreted by G. sulfurreducens and might participate in the bioreduction of Fe 3+ or transfer electrons to partner bacteria.…”