The closest thing to a within-study head-to-head of Geobacter nanowire candidates — Ye et al. (2022), deleting pili, OmcS and OmcZ in one framework — concluded a division of labor among them, not a single winner

electromicrobiologygeobactermicrobial-nanowirescytochromee-piliscientific-controversy

Ye, Liu, Nealson, Rensing, Qin and Zhou, "Dissecting the Structural and Conductive Functions of Nanowires in Geobacter sulfurreducens Electroactive Biofilms" (mBio, 2022), built targeted gene-deletion mutants removing pili (ΔpilB), OmcS (ΔomcS) and OmcZ (ΔomcZ) within a single experimental framework, then restored a non-conductive flagellum in the pili- and OmcZ-deficient strains to separate each filament's structural contribution (biofilm thickness) from its conductive contribution (current generation). This is the one source surfaced in this cluster that tests more than one proposed Geobacter nanowire candidate side by side, in the same strains under the same conditions — an actual experimental adjudication rather than a review of separately-run studies.

Its resolution is coexistence-with-division-of-labor, not elimination: "(i) the pili play only a structural role supporting the formation of a thick anode biofilm; (ii) OmcS plays only a conductive role in facilitating LET; and (iii) the OmcZ nanowire plays both conductive and structural roles, contributing to both biofilm formation and primary current generation." The abstract frames the field the same way, opening with the inventory — "Three types of nanowires have been identified: pili, OmcS, and OmcZ." — and closing, eight sentences later, on what the experiment settles: "These data support a model in which multiheme cytochromes facilitate long-distance electron transfer in G. sulfurreducens biofilms." It does not crown pili, OmcS or OmcZ as "the" wire.

The paper is itself a third research group (Fujian Agriculture and Forestry University / University of Southern California), distinct from both the Lovley and the Malvankar camps, and it is contested in both directions: its Discussion calls the rival secretory-pseudopili account of pili function (claim-geobacter-pili-are-secretory-pseudopili-not-nanowires) "unlikely" on structural grounds, while Lovley in turn published a direct reply ("Untangling Geobacter sulfurreducens Nanowires," mBio 2022, doi:10.1128/mbio.00850-22) disputing its demotion of e-pili — and the authors answered him back the same day ("Reply to Lovley," doi:10.1128/mbio.01041-22), so the 2022 round is a two-way exchange, not a critique left standing. So even this nearest-to-head-to-head study adds a fourth position to an already multi-sided fight rather than closing it — the dispute was still live as of the 2025 exchange (claim-2025-lovley-commentary-rebuts-cytochrome-review-geobacter-dispute-unresolved).