Cytochrome OmcS is not essential for long-range electron transport in<i>Geobacter sulfurreducens</i>strain KN400

Walker, David M.; Li, Yang; Meier, David; Pinches, Samantha; Holmes, Dawn E.; Smith, Jessica A.

doi:10.1101/2020.07.22.214791

Cited by 5 publications

(3 citation statements)

References 42 publications

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“…Furthermore, deleting omcS has no negative impact on biofilm conductivity or current production ( 15 , 31 ). Deletion of omcS can inhibit Fe(III) oxide reduction, in some, but not all variants of G. sulfurreducens ( 32 , 33 ). When deletion of omcS does have an impact, the strain can be rescued for Fe(III) oxide reduction with the addition of ultrafine-grained magnetite ( 34 ).…”

Section: Discussionmentioning

confidence: 99%

Direct Observation of Electrically Conductive Pili Emanating from Geobacter sulfurreducens

Liu

Walker

Nonnenmann

et al. 2021

mBio

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Electroactive microbes have significant environmental impacts, as well as applications in bioenergy and bioremediation. The composition, function, and even existence of electrically conductive pili (e-pili) has been one of the most contentious areas of investigation in electromicrobiology, in part because e-pili offer a mechanism for long-range electron transport that does not involve the metal cofactors common in much of biological electron transport.

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Section: Discussionmentioning

confidence: 99%

Direct Observation of Electrically Conductive Pili Emanating from Geobacter sulfurreducens

Liu

Walker

Nonnenmann

et al. 2021

mBio

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“…G. sulfurreducens strain Aro-5 cannot produce highly conductive biofilms or high current densities on anodes (18), whereas deleting omcS has no impact on these phenotypes (17, 29). Deletion of omcS can inhibit Fe(III) oxide reduction, in some, but not all variants of G. sulfurreducens (30, 31). When deletion of omcS does have an impact, the strain can be rescued for Fe(III) oxide reduction with the addition of ultrafine-grained magnetite (32).…”

Section: Discussionmentioning

confidence: 99%

Direct Observation of Electrically Conductive Pili Emanating fromGeobacter sulfurreducens

Liu

Walker

Nonnenmann

et al. 2021

Preprint

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Geobacter sulfurreducens is a model microbe for elucidating the mechanisms for extracellular electron transfer in several biogeochemical cycles, bioelectrochemical applications, and microbial metal corrosion. Multiple lines of evidence previously suggested that electrically conductive pili (e-pili) are an essential conduit for long-range extracellular electron transport in G. sulfurreducens. However, it has recently been reported that G. sulfurreducens does not express e-pili and that filaments comprised of multi-heme c-type cytochromes are responsible for long-range electron transport. This possibility was directly investigated by examining cells, rather than filament preparations, with atomic force microscopy. Approximately 90 % of the filaments emanating from wild-type cells had a diameter (3 nm) and conductance consistent with previous reports of e-pili harvested from G. sulfurreducens or heterologously expressed in E. coli from the G. sulfurreducens pilin gene. The remaining 10% of filaments had a morphology consistent with filaments comprised of the c-type cytochrome OmcS. A strain expressing a modified pilin gene designed to yield poorly conductive pili expressed 90 % filaments with a 3 nm diameter, but greatly reduced conductance, further indicating that the 3 nm diameter conductive filaments in the wild-type strain were e-pili. A strain in which genes for five of the most abundant outer-surface c-type cytochromes, including OmcS, was deleted yielded only 3 nm diameter filaments with the same conductance as in the wild-type. These results demonstrate that e-pili are the most abundant conductive filaments expressed by G. sulfurreducens, consistent with previous functional studies demonstrating the need for e-pili for long-range extracellular electron transfer.

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“…Therefore, OmcS facilitates direct contact with the solid extracellular electron donors and acceptors. However, it was shown that G. sulfurreducens strain KN400 did not require OmcS for DIET and Fe(III) oxide reduction, indicating that the requirement of OmcS for EET is strain specific (85).…”

Section: Outer Membranementioning

confidence: 99%

Cytochromes in Extracellular Electron Transfer in Geobacter

Ueki

2021

Appl Environ Microbiol

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Extracellular electron transfer (EET) is an important biological process in microbial physiology as found in dissimilatory metal oxidation/reduction and interspecies electron transfer in syntrophy in natural environments. EET also plays a critical role in microorganisms relevant to environmental biotechnology in metal-contaminated areas, metal corrosion, bioelectrochemical systems, and anaerobic digesters. Geobacter species exist in a diversity of natural and artificial environments. One of the outstanding features of Geobacter species is the capability of direct EET with solid electron donors and acceptors including metals, electrodes, and other cells. Therefore, Geobacter species are pivotal in environmental biogeochemical cycles and biotechnology applications. Geobacter sulfurreducens, a representative Geobacter species, has been studied for the direct EET as a model microorganism. G. sulfurreducens employs electrically conductive pili (e-pili) and c-type cytochromes for the direct EET. The biological function and electronics applications of the e-pili have been reviewed recently and this review focuses on the cytochromes. Geobacter species have an unusually large number of cytochromes encoded in their genomes. Unlike most other microorganisms, Geobacter species localize multiple cytochromes in each subcellular fraction: outer membrane, periplasm, and inner membrane, as well as in the extracellular space, and differentially utilize these cytochromes for the EET with various electron donors and acceptors. Some of the cytochromes are functionally redundant. Thus, the EET in Geobacter is complicated. Geobacter coordinates the cytochromes with other cellular components in the elaborate EET system to flourish in the environment.

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Cytochrome OmcS is not essential for long-range electron transport inGeobacter sulfurreducensstrain KN400

Cited by 5 publications

References 42 publications

Direct Observation of Electrically Conductive Pili Emanating from Geobacter sulfurreducens

Direct Observation of Electrically Conductive Pili Emanating from Geobacter sulfurreducens

Direct Observation of Electrically Conductive Pili Emanating fromGeobacter sulfurreducens

Cytochromes in Extracellular Electron Transfer in Geobacter

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