Final answer:
The pili of Bordetella pertussis are called fimbriae, which are key in its ability to attach to host cells and form biofilms, aiding in its pathogenicity.
Step-by-step explanation:
The pili of Bordetella pertussis, the bacteria responsible for whooping cough, are called fimbriae. These are short bristle-like proteins that project from the cell surface of the bacterium. Fimbriae play a crucial role in the bacterial infection process as they allow the bacterial cell to adhere to the host cells, which is important for colonization, infectivity, and virulence. B. pertussis uses fimbriae, not only to attach to host cells but also for the formation of biofilms, contributing to its pathogenicity.