Regulation of minD by oxyR in Neisseria gonorrhoeae

Abstract

In Neisseria gonorrhoeae, cytokinesis involves Escherichia coli homologues of minC, minD and minE which are encoded as part of a min operon. MinD, a 30 kD protein component of the MinC-MinD septum inhibitory complex, together with MinE, mediates cell division site selection. Gonococci mutated in minD display aberrant cytokinesis, abnormal morphology, defective microcolony formation and virulence. minD is 274 bp upstream of oxyR, another min operon gene in N. gonorrhoeae, which encodes a redox-responsive transcriptional regulator implicated in responses to oxidative stress. In this study, we aimed to examine the oxyR-mediated regulation of minD. We observed the cotranscription of oxyR with the minCDE gene cluster. The mutation of oxyR resulted in non-midline formation of the division septum, anomalous DNA segregation, and increased aggregation of bacterial cells. qRT-PCR and Western Blot analysis revealed upregulation of minD in an oxyR mutant as compared to its isogenic wild-type N. gonorrhoeae strain in stationary phase. Furthermore, the exposure to oxidative stress in the form of H2O2 increased MinD expression levels in wild-type N. gonorrhoeae. Using β-galactosidase activity-based promoter assays, we found that oxyR negatively regulates the promoter region (PminD) upstream of minD. Our results demonstrate the involvement of oxyR in cell division and minD expression in N. gonorrhoeae.