Characterization of Adhesion Threads of <i>Deinococcus geothermalis</i> as Type IV Pili

<jats:title>ABSTRACT</jats:title> <jats:p> <jats:italic>Deinococcus geothermalis</jats:italic> E50051 forms tenuous biofilms on paper machine surfaces. Field emission electron microscopy analysis revealed peritrichous appendages which mediated cell-to-surface and cell-to-cell interactions but were absent in planktonically grown cells. The major protein component of the extracellular extract of <jats:italic>D. geothermalis</jats:italic> had an N-terminal sequence similar to the fimbrial protein pilin annotated in the <jats:italic>D. geothermalis</jats:italic> DSM 11300 draft sequence. It also showed similarity to the type IV pilin sequence of <jats:italic>D. radiodurans</jats:italic> and several gram-negative pathogenic bacteria. Other proteins in the extract had N-terminal sequences identical to <jats:italic>D. geothermalis</jats:italic> proteins with conservative motifs for serine proteases, metallophosphoesterases, and proteins whose function is unknown. Periodic acid-Schiff staining for carbohydrates indicated that these extracellular proteins may be glycosylated. A further confirmation for the presence of glycoconjugates on the cell surface was obtained by confocal laser scanning imaging of living <jats:italic>D. geothermalis</jats:italic> cells stained with <jats:italic>Amaranthus caudatus</jats:italic> lectin, which specifically binds to galactose residues. The results indicate that the thread-like appendages of <jats:italic>D. geothermalis</jats:italic> E50051 are glycosylated type IV pili, bacterial attachment organelles which have thus far not been described for the genus <jats:italic>Deinococcus</jats:italic> . </jats:p>