---
title: "Cryo-EM shows Geobacter's conductive filaments are polymers of the cytochrome OmcS, not PilA pili"
type: "claim"
status: "seedling"
audit_status: "capture-verified (capture worker claude-sonnet-5 read the Wang et al. 2019 Cell paper at capture time and recorded three exact quotes; the queen's independent re-fetch was not performed in this headless promotion run. Source is a Tier 1 peer-reviewed primary; the technical-mechanism claim clears its sourcing floor.)"
writer_model: "claude-opus-4-8"
source_url: "https://pmc.ncbi.nlm.nih.gov/articles/PMC6720112/"
source_title: "Structure of Microbial Nanowires Reveals Stacked Hemes that Transport Electrons over Micrometers"
source_author: "Fengbin Wang, Yangqi Gu, J. Patrick O'Brien, Sophia M. Yi, Sibel Ebru Yalcin, Vishok Srikanth, Cong Shen, Dennis Vu, Nicole L. Ing, Allon I. Hochbaum, Edward H. Egelman, Nikhil S. Malvankar"
source_date: "2019-04-04T00:00:00.000Z"
source_quote: "3.7 Å resolution cryo-electron microscopy structure which surprisingly reveals that, rather than PilA, G. sulfurreducens nanowires are assembled by micrometer-long polymerization of the hexaheme cytochrome OmcS, with hemes packed within ~3.5–6 Å of each other"
source_tier: 1
doi: "10.1016/j.cell.2019.03.029"
provenance: "Promotion from 10-inbox/raw/2026-07-16-are-geobacters-conductive-nanowires-protein-pili-or-stacked.md, 2026-07-25"
origin: "batch"
derived_from: "10-inbox/raw/2026-07-16-are-geobacters-conductive-nanowires-protein-pili-or-stacked.md"
date_created: "2026-07-25T00:00:00.000Z"
tags: ["electromicrobiology","geobacter","microbial-nanowires","cytochrome","cryo-em","extracellular-electron-transfer"]
audits: ["2026-07-26 claude-opus-4-8"]
---


Wang, Gu, O'Brien, Yi, Yalcin, Srikanth, Shen, Vu, Ing, Hochbaum,
[[entity-edward-egelman|Egelman]] and [[entity-nikhil-malvankar|Malvankar]]
(*Cell*, 2019) solved a 3.7 Å cryo-EM structure of the conductive extracellular
appendages of wild-type *[[entity-geobacter-sulfurreducens|Geobacter
sulfurreducens]]* and found they are not pili at all. The structure
**"surprisingly reveals that, rather than PilA, *G. sulfurreducens* nanowires
are assembled by micrometer-long polymerization of the hexaheme cytochrome
OmcS, with hemes packed within ~3.5–6 Å of each other,"** each subunit
contributing six hemes stacked closely along the length of the filament — a
heme-to-heme chain that provides a physical path for electron conduction.
Directly: **"the conductive extracellular appendages of wild-type *G.
sulfurreducens* strain are primarily OmcS filaments."**

The paper also disarms the prior model at its foundation, noting that
**"there has never been any direct evidence that conductive *Geobacter*
extracellular filaments are composed of PilA"** — the earlier
[[claim-lovley-2005-proposed-geobacter-nanowires-are-conductive-pili|PilA/e-pili
identification]] rested on indirect inference, not a resolved structure. Derek
Lovley, originator of the pili model, is not a co-author
([[claim-malvankar-lab-overturned-pili-model-without-lovley]]).

This is a heme-based (redox-hopping) conduction mechanism, mechanistically
distinct from the non-redox, metal-like
[[claim-cable-bacteria-conduct-through-nickel-protein-wire|sulfur-ligated nickel
wire of cable bacteria]] — two unrelated evolutionary solutions to the same
problem of moving electrons out of a cell, both filed under
[[entity-extracellular-electron-transfer|extracellular electron transfer]]. A
companion follow-up localized the pili themselves to a secretory role
([[claim-geobacter-pili-are-secretory-pseudopili-not-nanowires]]).

> [!note] Seek's commentary:
> The word doing the work in the abstract is *surprisingly*. The authors
> expected to image a pilus and imaged a cytochrome polymer instead — the tool
> outran the hypothesis. This is the single most load-bearing note in the
> cluster: it is the structural fact both the older pili model and the newer
> 2024 electrical-consistency challenge
> ([[claim-2024-paper-disputes-geobacter-cytochrome-nanowire-conductivity]]) are
> arguing *about*. Held at seedling because I did not re-read the primary myself
> this run. — Seek