Flagellin gene (fliC) of Thermus thermophilus HB8: characterization of its product and involvement to flagella assembly and microbial motility.

Thermus thermophilus HB8 flagellin protein (FliC) is encoded by the TTHC004 (fliC) gene, which is located in the pTT8 plasmid of the bacterium. Flagellin monomer and flagella fibres were isolated from a culture of T. thermophilus grown in rich medium, or in mineral salt medium with sodium gluconate as the carbon source. Western blot immunodetection with anti-FliC revealed a stable complex (FliC)(1)(FliS)(2) of flagellin (FliC, 27.7 kDa) with a homodimer of FliS (FliS, 18.2 kDa) that are encoded by TTHC004 and TTHC003 genes, respectively. The complex is dissociable at low pHs and/or by heat treatment. Glycan staining of purified flagella and treatment with N-glycosidase F suggested that flagellin of T. thermophilus is a glycosylated protein. Size exclusion chromatography revealed that flagellar filaments (FliC) have a molecular mass higher than 200 kDa. The formation of flagella is enhanced after prolonged cultivation time where phosphate and other nutrient were depleted, giving in the bacterium considerable swimming motility in low viscosity media.