---
title: "Does Guberman-Pfeffer (2024) show Geobacter cytochrome nanowire conductivities exceed the redox-current maximum by 10²–10⁵-fold?"
type: "question"
status: "answered"
writer_model: "claude-opus-4-8"
date_raised: "2026-07-25T00:00:00.000Z"
answered_log: "2026-08-07 — Answered. The '10²–10⁵-fold' magnitude is confirmed against the primary: verbatim-verified in a 2026-07-26 opus audit of [[claim-2024-paper-disputes-geobacter-cytochrome-nanowire-conductivity]] (which resolved that note's [unverified-quant] flag), and independently re-confirmed at the 2026-08-07 capture against a freshly-archived primary (source_sha 3a3a978b85…). The compared quantities are now captured: measured currents versus a computed maximum redox current of 0.14 pA/filament, itself a Marcus-theory result rather than a separate measurement ([[claim-guberman-pfeffer-0-14-pa-ceiling-is-computed-not-measured]]). The paper attributes the mismatch to abiological measurement conditions, not to the cytochrome identity being wrong ([[claim-guberman-pfeffer-blames-measurement-not-cytochrome-identity]]). The optional second leg — whether a later paper rebuts or concedes the redox-current-ceiling argument — is left as future reading, not a blocker; it does not keep this specific verification open."
tags: ["electromicrobiology","geobacter","cytochrome","needs-primary","unverified-quant"]
---


## The question

[[claim-2024-paper-disputes-geobacter-cytochrome-nanowire-conductivity]] rests
on a specific magnitude: that the measured conductivities of *Geobacter*
OmcS/OmcZ cytochrome nanowires are "10²–10⁵-fold larger than the computed and
biologically reasonable maximum redox current." Does the primary paper actually
state this figure, and in what terms?

## Why it matters

This is the load-bearing number behind the claim that the *Geobacter* nanowire
dispute is **not fully settled** — the fourth position in a multi-party
controversy (see [[claim-malvankar-lab-overturned-pili-model-without-lovley]]).
If the magnitude is real and stands, the cytochrome-nanowire model has an
unresolved physics problem even though its *structure* is well resolved
([[claim-geobacter-conductive-filaments-are-omcs-cytochrome-polymers]]). The
number therefore decides whether the vault should present the cytochrome model
as "leading and essentially settled" or "leading but electrically contested."

## Why it is a question and not yet verified

The 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 re-fetched in the promotion run. The source venue (*Frontiers
in Microbiology*, peer-reviewed) clears the Tier 1–2 floor for a quantitative
claim, but the specific number has not been confirmed against the paper's own
text this session.

## What would answer it

- Fetch the primary — Guberman-Pfeffer, "To be or not to be a cytochrome...,"
  *Frontiers in Microbiology* (2024), DOI 10.3389/fmicb.2024.1397124, at
  https://pmc.ncbi.nlm.nih.gov/articles/PMC11021709 — and confirm the
  "10²–10⁵-fold" magnitude and exactly what quantities it compares (measured
  conductivity vs. computed maximum redox current).
- Optionally, check whether any later paper (Malvankar-lineage or third-party)
  rebuts or concedes the redox-current-ceiling argument, which would move the
  parent claim toward "settled" or "still open."

Routed from the promotion of
[[10-inbox/raw/2026-07-16-are-geobacters-conductive-nanowires-protein-pili-or-stacked]]
(2026-07-25).

> [!note] Correction annotation — 2026-09-16 (propagation-repair)
> The `answered_log` above says the paper attributes the mismatch to abiological measurement conditions, "not to the cytochrome identity being wrong". That exclusive has been withdrawn. Corrected value: Guberman-Pfeffer affirms that the filaments are cytochromes and aims the critique mainly at the measurements. But his stated conclusion is disjunctive. It leaves open that "the conformation or composition of the characterized proteins is something other than the known cytochrome filaments". The abstract cites "sample impurities", and the paper says the failure to reconcile the numbers "lends circumstantial support to the e-pilus hypothesis." This propagates the 2026-08-08 and 2026-08-10 corrections of [[claim-guberman-pfeffer-blames-measurement-not-cytochrome-identity]], whose title was restated to match. The historical answer text is left as given.


## Progress log

- 2026-08-07 — Answered. The '10²–10⁵-fold' magnitude is confirmed against the primary: verbatim-verified in a 2026-07-26 opus audit of [[claim-2024-paper-disputes-geobacter-cytochrome-nanowire-conductivity]] (which resolved that note's [unverified-quant] flag), and independently re-confirmed at the 2026-08-07 capture against a freshly-archived primary (source_sha 3a3a978b85…). The compared quantities are now captured: measured currents versus a computed maximum redox current of 0.14 pA/filament, itself a Marcus-theory result rather than a separate measurement ([[claim-guberman-pfeffer-0-14-pa-ceiling-is-computed-not-measured]]). The paper attributes the mismatch to abiological measurement conditions, not to the cytochrome identity being wrong ([[claim-guberman-pfeffer-blames-measurement-not-cytochrome-identity]]). The optional second leg — whether a later paper rebuts or concedes the redox-current-ceiling argument — is left as future reading, not a blocker; it does not keep this specific verification open.