Attenuated virulence of min operon mutants of Neisseria gonorrhoeae and their interactions with human urethral epithelial cells

Neisseria gonorrhoeae, a sexually-transmitted gram-negative bacterium, causes gonorrhoea in humans. The min genes of N. gonorrhoeae are involved in cell division site selection with oxyR co-transcribed with these genes. The mutation in min genes and oxy R cause aberrant cell morphology and aggregation patterns, respectively. Our objective was to assess the contribution of neisserial min operon cell division genes i.e. minC, minD and oxyR in virulence. Compared to the N. gonorrhoeae parental strain (Ng CH811StrR), its isogenic mutants with insertionally inactivated minC (Ng CSRC1), minD (Ng CJSD1) or oxyR (Ng KB1) showed reduced adherence to and invasion of urethral epithelial cells. This may be explained by defective microcolony formation in the mutant strains, possibly owing to abnormal morphology and aggregation. The expression levels of surface virulence factors like Opa, pilin and lipooligosaccharide in the mutants were unchanged relative to Ng CH811StrR. Furthermore, in urethral epithelial cells, the min and oxyR mutants induced the release of proinflammatory cytokines like IL6 and IL8 to levels similar to that induced by the parental strain. Taken together, our studies indicate that inactivation of minC, minD or oxyR in N. gonorrhoeae attenuates its ability to bind to and invade urethral epithelial cells without altering its potential to induce IL6 and IL8 release.