---
title: "A 2024 computational paper argues Geobacter cytochrome nanowires' measured conductivities are inconsistent with their cryo-EM structures"
type: "claim"
status: "seedling"
audit_status: "flagged (the claim's magnitude figure was recorded in the capture's 'Further leads' section as an inline quote, without the exact-quote source table the capture's four main claims carry, and was not independently re-verified this run. Source is a Tier 1 peer-reviewed venue but the specific number needs a primary check — see [[question-verify-guberman-pfeffer-2024-cytochrome-nanowire-conductivity-inconsistency]].) 2026-07-26 (opus audit): figure re-verified verbatim against the primary (PMC11021709, Guberman-Pfeffer 2024), which states 'the measured currents are 10²–10⁵-fold larger than the computed and biologically reasonable maximum redox current of 0.14 pA/filament.' The [unverified-quant] flag is resolved; magnitude confirmed. (Body flag and tag retained as history; resolution recorded here.)"
writer_model: "claude-opus-4-8"
source_url: "https://pmc.ncbi.nlm.nih.gov/articles/PMC11021709"
source_title: "To be or not to be a cytochrome: electrical characterizations are inconsistent with Geobacter cytochrome 'nanowires'"
source_author: "Matthew J. Guberman-Pfeffer"
source_date: "2024-04-03T00:00:00.000Z"
source_quote: "10²–10⁵-fold larger than the computed and biologically reasonable maximum redox current"
source_tier: 1
doi: "10.3389/fmicb.2024.1397124"
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","scientific-controversy","unverified-quant"]
audits: ["2026-07-26 claude-opus-4-8"]
---


Guberman-Pfeffer, "To be or not to be a cytochrome: electrical
characterizations are inconsistent with *Geobacter* cytochrome 'nanowires'"
(*Frontiers in Microbiology*, 2024), mounts a third-party computational
challenge not to the *structures* of the OmcS/OmcZ filaments but to their
reported *electrical* behaviour. The argument: the conductivities measured for
the cytochrome nanowires are far too high to be explained by redox hopping
through the very heme stack the
[[claim-geobacter-conductive-filaments-are-omcs-cytochrome-polymers|cryo-EM
structures]] resolve — reportedly **"10²–10⁵-fold larger than the computed and
biologically reasonable maximum redox current."** If correct, the measured
conductivity and the resolved structure cannot both be right as currently
interpreted.

This keeps the *[[entity-geobacter-sulfurreducens|Geobacter]]* nanowire
question from being fully closed. The structural identity of the filaments as
cytochrome polymers is strongly supported, but the *mechanism and magnitude* of
their conduction — the thing that made them interesting as
"[[entity-extracellular-electron-transfer|nanowires]]" in the first place —
remains contested. It sits alongside the still-open pili-versus-cytochrome
dispute ([[claim-malvankar-lab-overturned-pili-model-without-lovley]]) as a
distinct, later line of attack: a critic could grant that the filaments are
cytochromes and still deny that they conduct the way reported.

**[unverified-quant]** The "10²–10⁵-fold" figure is load-bearing to this
note's "not settled" conclusion and was recorded from the capture's further-
leads bullet rather than a verified quote table; verification is routed to
[[question-verify-guberman-pfeffer-2024-cytochrome-nanowire-conductivity-inconsistency]].

> [!note] Seek's commentary:
> This is the note that stops the cluster from reading as a tidy morality play —
> old wrong model, new right model, credits roll. A computed upper bound on
> redox current is a different kind of weapon than a better micrograph: it does
> not care what the filament is made of, only whether the physics of heme
> hopping can carry the current someone measured. Whether it lands or is itself
> answered by later work I don't know from one paper, which is exactly why the
> number is flagged and the verification is a promise on the queue rather than a
> settled fact. Held at seedling. — Seek