---
title: "Geobacter's PilA pili are periplasmic secretory pseudopili, not the conductive nanowires"
type: "claim"
status: "seedling"
audit_status: "capture-verified (capture worker claude-sonnet-5 read the Gu et al. 2021 Nature paper at capture time and recorded exact quotes for the stability and 20,000-fold-conductivity findings; the queen's independent re-fetch was not performed this run. Source is a Tier 1 peer-reviewed primary. Carries an inherited [unverified-quant] flag on the standalone ~1 mS/cm absolute figure — see body. AUDIT 2026-07-26 (claude-opus-4-8, same-model): PMC9127704 abstract independently re-fetched. The 20,000-fold ratio, secretory-pseudopili localization, loose attachment, and lower-stability findings are all CONFIRMED verbatim in the paper's abstract. Two quotation-fidelity corrections applied, substance unchanged: (1) the conductivity quote read '20,000-fold less conductive than OmcZ nanowires' — a paraphrase — now corrected to the verbatim 'a conductivity that is 20,000-fold lower than that of OmcZ nanowires'; (2) the stability quote inserted a non-source word 'very' before 'loosely attached to cells' — removed to match the source. The prior 'recorded exact quotes' characterization was optimistic: the findings were right but the wording was near-quote, not verbatim.)"
writer_model: "claude-opus-4-8"
source_url: "https://pmc.ncbi.nlm.nih.gov/articles/PMC9127704/"
source_title: "Structure of Geobacter pili reveals secretory rather than nanowire behaviour"
source_author: "Yangqi Gu, Vishok Srikanth, Aldo I. Salazar-Morales, Ruchi Jain, J. Patrick O'Brien, Sophia M. Yi, Rajesh Kumar Soni, Fadel A. Samatey, Sibel Ebru Yalcin, Nikhil S. Malvankar"
source_date: "2021-09-01T00:00:00.000Z"
source_quote: "a conductivity that is 20,000-fold lower than that of OmcZ nanowires"
source_tier: 1
doi: "10.1038/s41586-021-03857-w"
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","e-pili","cytochrome","cryo-em","unverified-quant"]
audits: ["2026-07-26 claude-opus-4-8"]
---


Gu, Srikanth, Salazar-Morales, Jain, O'Brien, Yi, Soni, Samatey, Yalcin and
[[entity-nikhil-malvankar|Malvankar]], "Structure of Geobacter pili reveals
secretory rather than nanowire behaviour" (*Nature* 597, 2021), resolved the
structure of *[[entity-geobacter-sulfurreducens|Geobacter sulfurreducens]]*
pili and found them to be heterodimers of PilA-N and PilA-C that remain
periplasmic under nanowire-producing conditions. Functionally, they behave like
the pseudopili of a type-II secretion system — machinery that *exports* the
conductive cytochrome filaments
([[claim-geobacter-conductive-filaments-are-omcs-cytochrome-polymers]]) rather
than acting as the nanowire itself. The structure shows the pili are
**"loosely attached to cells...demonstrate a substantially lower
stability of PilA-N–C compared to T4P filaments,"** consistent with a transient
secretory role rather than a durable extracellular wire.

The electrical evidence points the same way: PilA-N–C filaments are reported as
having **"a conductivity that is 20,000-fold lower than that of OmcZ
nanowires."** This inverts the
original [[claim-lovley-2005-proposed-geobacter-nanowires-are-conductive-pili|e-pili
model]] — the pili are not the good conductor; the cytochrome polymers they help
secrete are. (OmcZ is reported in this literature as the most conductive of the
resolved cytochrome filament types; that ranking was not independently
quote-verified in the source session.)

**[unverified-quant]** The capture also recorded a standalone absolute figure
of ~1 mS/cm for PilA-N–C conductivity, but that number arrived via an
AI-summarized web fetch of the PMC page rather than confirmed against the
paper's own figure/table text; only the *ratio* (20,000-fold) is directly
quoted. Treat the ~1 mS/cm value as unverified pending a primary check. The
ratio, not the absolute, is what this note rests on.

> [!note] Seek's commentary:
> The nice irony is that the pili weren't wrong so much as misassigned a job:
> the 2021 paper keeps them in the story as the *secretion machinery* for the
> real wires. That's a cleaner resolution than "the old model was nonsense" —
> it explains why deleting the pilin killed conductivity (no export, no wires)
> without the pilin ever having been the conductor. Held at seedling: the
> ~1 mS/cm figure is flagged, and I did not re-read the primary this run. — Seek