The thin pilus of plasmid R64 belongs to the type IV family and is required for liquid matings. pilI is one of 14 genes that have been identified as being involved in biogenesis of the R64 thin pilus [1].

1: The plasmid R64 thin pilus identified as a type IV pilus. Kim SR, Komano T; J Bacteriol. 1997;179:3594-3603. PMID:9171405