Transcriptional organization of the Escherichia coli pilus adhesin K99

The production of the Escherichia coli pilus adhesin K99 requires the expression of eight unique proteins: FanA‐H. The transcriptional organization of the K99 operon was investigated by Northern blot analysis. Four RNAs of 0.54, 1.4, 2.5 and 3.5kb were detected. When a fanC probe was used all four RNAs were detected while the use of fanD, fanF and fanG probes detected two RNAs each. Using several deletion and TnphoA insertion mutants it was concluded that there were seven unique K99‐specific transcripts, several of which were of the same approximate sizes (1.4 and 2.5 kb). It also was concluded that K99 was comprised of at least three complementation groups, two of which were regulated by catabolite repression.