While questions remain about how common bacterial nanotubes are and what they do, researchers have identified key differences in their structure and function that set them apart from pili used for mating, injectisomes that transfer virulence proteins, and flagella that power swimming in many microbes.
Bacterial Nanotubes
Conjugative Pili
Type 3 Secretion Systems, e.g., Injectisomes and Flagella
Lipids; segmented
Proteins; helical
Multiprotein complex; tubular
1–40 μm
1–2 μm
0.8–2 μm
30–130 nm; commonly 40–70 nm
6–11 nm; lumen diameter ~3 nm
8–10 nm; lumen diameter ~2.5 nm
Antibiotic resistance factors, metabolites, toxins
Plasmids
Injectisomes for the transfer of virulence proteins; flagella for motility
CORE complex (same proteins as the flagellar base) and hydrolases that help make a hole in the cell wall
“Transfer” (Tra) class of proteins such as pilin, TraL, and TraF
The injectisome complex has various proteins such as secretin, stalk protein, and needle filament; the flagellar apparatus ...
