9SIE

Structure of the bacterial archaellum from L. aerophila

Summary for 9SIE

• Entry DOI: 10.2210/pdb9sie/pdb
• EMDB information: 54927
• Descriptor: Flagellin (1 entity in total)
• Functional Keywords: helical, cell surface structure, motility, archaellum, protein fibril
• Biological source: Litorilinea aerophila
• Total number of polymer chains: 17
• Total formula weight: 330967.15

Authors

Sivabalasarma, S.,Taib, N.,Mollat, C.L.,Joest, M.,Steimle, S.,Gribaldo, S.,Albers, S.-V. (deposition date: 2025-08-28, release date: 2026-01-28)

Primary citation

Sivabalasarma, S.,Taib, N.,Mollat, C.L.,Joest, M.,Steimle, S.,Gribaldo, S.,Albers, S.V.
Structure of a functional archaellum in Bacteria of the Chloroflexota phylum.
Nat Microbiol, 10:2412-2424, 2025

PubMed Abstract: Motility in Archaea is driven by the archaellum, a rotary ATP-driven machinery unrelated to the bacterial flagellum. To date, archaella have been described exclusively in archaea; however, recent work reported archaellum genes in bacterial strains of the SAR202 clade (Chloroflexota). Here, using MacSyFinder, we show that bona fide archaellum gene clusters are widespread in several members of the Chloroflexota. Analysis of archaellum-encoding loci and Alphafold3-predicted structures show similarity to the archaellum machinery. Using cryo electron microscopy single-particle analysis, we solved the structure of the bacterial archaellum from Litorilinea aerophila to 2.7 Å. We also show the expression and assembly of this machinery in bacteria and its function in swimming motility. Finally, a phylogenomic analysis revealed two horizontal gene transfer events from euryarchaeal members to Chloroflexota. In summary, our study shows that a functional and assembled archaellum machinery can be exchanged between the two prokaryotic domains.

PubMed: 40962902
DOI: 10.1038/s41564-025-02110-8

Experimental method

ELECTRON MICROSCOPY (2.7 Å)