ABSTRACTNeisseria meningitidishistorically has been an infrequent and sporadic cause of urethritis and other urogenital infections. However, a nonencapsulated meningococcal clade belonging to the hyperinvasive clonal complex 11.2 lineage has recently emerged and caused clusters of urethritis cases in the United States and other countries. One of the genetic signatures of the emergingN. meningitidisurethritis clade (NmUC) is a chromosomal gene conversion event resulting in the acquisition of theNeisseria gonorrhoeaedenitrification apparatus—theN. gonorrhoeaealleles encoding the nitrite reductase AniA, the nitric oxide (NO) reductase NorB, and the intergenic promoter region. The biological importance of theN. gonorrhoeaeAniA-NorB for adaptation of theNmUC to a new environmental niche is investigated herein. We found that oxygen consumption, nitrite utilization, and NO production were significantly altered by the conversion event, resulting in different denitrifying aerobic and microaerobic growth of the clade. Further, transcription ofaniAandnorBinNmUC isolates differed from canonicalN. meningitidis, and important polymorphisms within the intergenic region, which influencedaniApromoter activity of theNmUC, were identified. The contributions of three known meningococcal regulators (NsrR, FNR, and NarQP) in controlling the denitrification pathway and endogenous NO metabolism were distinct. Overall, transcription ofaniAwas dampened relative to canonicalN. meningitidis, and this correlated with the lower NO accumulation in the clade. Denitrification and microaerobic respiration were bolstered, and protection against host-derived NO was likely enhanced. The acquisition of theN. gonorrhoeaedenitrification pathway by theNmUC supports the clade’s adaptation and survival in a microaerobic urogenital environment.