Organization of the X. fastidiosa unique pilin/fimbriae cluster in the four strains. Yellow color arrows represent genes with clear functions and white color arrows, hypothetical genes. A Pilin biogenesis cluster. The ORF XF0028 codes for a pili retraction PilT protein, involved in the supply of energy for cell motility ; ORF, XF0029 codes for a pre-pili leader sequence; XF0030 is a hypothetical protein; XF0031 codes for the pili assembly protein PilX protein, which is a pilus-associated protein essential for bacterial aggregation and is a key to pilus-facilitated attachment to human cells ; XF0032 codes for a PilY1 protein, which is thought to be a fimbrial tip-associated adhesion, and involved in fimbrial assembly ; XF0033 codes for membrane scaffold protein PilE subunits, which are packed to form a hydrophobic core of microtubules . This 7-kb DNA fragment contains genes responsible for type IV pili biogenesis was also found in Temecula-1.B Fimbriae cluster. XF0077 and XF0078 are both C chain precursors of type-1 fimbrial proteins while XF0080 is a C chain precursor of type-1 fimbrial protein; XF0079 is a hypothetical protein; XF0081 is an outer membrane usher protein fimC; XF0082 is a chaperone protein ecpD and XF0083 is the major pilin protein fimA.