Iron availability regulates DNA recombination in Neisseria gonorrhoeae

The pilus of Neisseria gonorrhoeae (the gonococcus Gc), the causative agent of gonorrhoea, promotes attachment of the gonococcus to the host epitheliu m and is essential for the establishment of disease. The ability of N. gono rrhoeae to infect previously exposed individuals is partially due to pilus antigenic variation. In addition, variation of the pilus has been proposed to function in the adaptation of the gonococcus to host environments. Previ ously, we described the development of a competitive reverse transcriptase (RT)-PCR assay that quantifies the frequency of pilin antigenic variation w ithin a gonococcal population. Using this assay, the effect of different bi ologically relevant environmental conditions on the frequency of pilin anti genic variation was tested. Of the environmental conditions examined in vit ro, only limited iron affected a significant change in the frequency of ant igenic variation. Further investigation revealed that an observed increase in pilin antigenic variation reflected an increase in other DNA recombinati on and DNA repair processes within iron-starved cultures. In addition, this low iron-induced increase was determined to be independent of changes in R ecA expression and was observed in a Fur mutant strain. As gonococci encoun ter conditions of low iron during infection, these data suggest that iron-l imitation signals for increased recombinational events that are important f or gonococcal pathogenesis.