A 2024 computational paper argues Geobacter cytochrome nanowires' measured conductivities are inconsistent with their cryo-EM structures

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 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 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 "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.