Differential roles of homologous recombination pathways in Neisseria gonorrhoeae pilin antigenic variation, DNA transformation and DNA repair

Neisseria gonorrhoeae (Gc) pill undergo antigenic variation when the amino acid sequence of the pilin protein is changed, aiding in immune avoidance a nd altering pilus expression. Pilin antigenic variation occurs by RecA-depe ndent unidirectional transfer of DNA sequences from a silent pilin locus to the expressed pilin gene through high-frequency recombination events that occur at limited regions of homology. We show that the Gc recQ and recO gen es are essential for pilin antigenic and phase variation and DNA repair but are not involved in natural DNA transformation. This suggests that a RecF- like pathway of recombination exists in Gc. In addition, mutations in the G c recB, recC or recD genes revealed that a Gc RecBCD pathway also exists an d is involved in DNA transformation and DNA repair but not in pilin antigen ic variation.