Mediates both adhesion to and invasion of human intestine epithelial cells. Also mediates bacterial cell aggregation via intercellular TibA-TibA interaction. Enhances biofilm formation. The cleaved C-terminal fragment (autotransporter domain) is localized in the outer membrane. The signal peptide, cleaved at the inner membrane, guides the autotransporter protein to the periplasmic space. Then, insertion of the C-terminal translocator domain in the outer membrane forms a hydrophilic pore for the translocation of the passenger domain to the bacterial cell surface, with subsequent cleavage (By similarity). Glycosylated by TibC. Glycosylation is required for TibA-mediated adhesion and invasion of human cells but not for aggregation. TibA-mediated aggregation is blocked upon capsule expression and fimbriation and is sensitive to pH extremes.