Sequence comparison indicates that the archaeal flagellum is homologous to bacterial Type IV pili, filamentous structures outside the cell. Pilus retraction provides enables a different form of bacterial motility called "twitching" or "social gliding" which allows bacterial cells to crawl along a surface, They are assembled through the Type II secretion system. They can also promote swimming, but no species of bacteria is known to use its Type IV pili for both swimming and crawling.
sequence comparison indicates that the archaeal flagellum is homologous to bacterial type iv pili filamentous structures outside the cell pilus retraction provides enables a different form of bacterial motility called "twitching" or "social gliding" which allows bacterial cells to crawl along a surface they are assembled through the type ii secretion system they can also promote swimming but no species of bacteria is known to use its type iv pili for both swimming and crawling