The electrically conductive pili of pecies are a recently evolved feature for extracellular electron transfer.

TitleThe electrically conductive pili of pecies are a recently evolved feature for extracellular electron transfer.
Publication TypeJournal Article
Year of Publication2016
AuthorsHolmes DE, Dang Y, Walker DJF, Lovley DR
JournalMicrob Genom
Date Published2016 Aug
KeywordsElectromagnetic Phenomena, Electron Transport, Ferric Compounds, Fimbriae Proteins, Fimbriae, Bacterial, Geobacter, Phylogeny

The electrically conductive pili (e-pili) of have environmental and practical significance because they can facilitate electron transfer to insoluble Fe(III) oxides; to other microbial species; and through electrically conductive biofilms. E-pili conductivity has been attributed to the truncated PilA monomer, which permits tight packing of aromatic amino acids to form a conductive path along the length of e-pili. In order to better understand the evolution and distribution of e-pili in the microbial world, type IVa PilA proteins from various Gram-negative and Gram-positive bacteria were examined with a particular emphasis on Fe(III)-respiring bacteria. E-pilin genes are primarily restricted to a tight phylogenetic group in the order Desulfuromonadales. The downstream gene in all but one of the Desulfuromonadales that possess an e-pilin gene is a gene previously annotated as '' that has characteristics suggesting that it may encode an outer-membrane protein. Other genes associated with pilin function are clustered with e-pilin and '' genes in the Desulfuromonadales. In contrast, in the few bacteria outside the Desulfuromonadales that contain e-pilin genes, the other genes required for pilin function may have been acquired through horizontal gene transfer. Of the 95 known Fe(III)-reducing micro-organisms for which genomes are available, 80 % lack e-pilin genes, suggesting that e-pili are just one of several mechanisms involved in extracellular electron transport. These studies provide insight into where and when e-pili are likely to contribute to extracellular electron transport processes that are biogeochemically important and involved in bioenergy conversions.

Alternate JournalMicrob Genom
PubMed ID28348867
PubMed Central IDPMC5320591