Do all bacteria have conjugation pili?

No, not all bacteria have conjugation pili. Conjugation pili are specific to bacteria that can engage in conjugation and are encoded by conjugative plasmids. While Gram-negative bacteria often use pili to transfer DNA, Gram-positive bacteria use other mechanisms, such as surface proteins, for conjugation. Furthermore, some bacteria may not possess the genetic elements required for conjugation and, therefore, lack conjugation pili altogether.