Molecular characterization of nitrite reductase gene (aniA) and gene product in Neisseria meningitidis isolates: Is aniA essential for meningococcal survival?

Abstract

SummaryThe present study evaluates sequence conservation in the gene coding for nitrite reductase (aniA) and AniA expression from a panel of Neisseria meningitidis isolates. Sequence analysis of the coding region in 19 disease-associated and 4 carrier strains notwithstanding a high degree of sequence similarity showed a number of nucleotide changes, some of which possibly resulted in premature translation termination or function loss. In particular, in one disease-associated strain a 9-residues insertion was found to be located close to the type I Cu-site and a catalytic histidine at position 280 was mutated into a leucine. In two strains from carriers, a sequence corresponding to a portion of a transposase gene within the aniA was also found. The AniA protein was always expressed, except for these two carriers strains and for other two strains in which the presence of the premature stop codons was recognized. The biochemical properties of the cloned soluble domain of the enzyme (sAniA) from N. meningitidis reference MC58 strain and from a clinical invasive isolate were studied. In particular, biochemical analysis of sAniA from MC58 demonstrated a clear dependence of its catalytic activity upon acidification, while the clinical isolatederived sAniA was not functional. Thus, the results obtained suggest that the presence of a conserved and functional aniA gene is not essential for meningococcal survival.

Emergence of a new Neisseria meningitidis clonal complex 11 lineage 11.2 clade as an effective urogenital pathogen

“…2D). Results of anaerobic nitrite-dependent growth assays correlated with the differences between meningococci and gonococci in the efficiency of the AniA/NorB systems (28). The US_NmUC isolates yielded substantial growth around the nitrite disk similar to that observed for Ng FA1090 (a representative CNM10 shown in Fig.…”

“…2A). In contrast, meningococci less commonly experience anaerobic conditions, and a functional denitrification pathway is not essential for their survival in the nasopharynx (28,29). Many meningococcal isolates have frame-shift mutations in aniA (29) and cannot grow anaerobically using nitrite as the electron acceptor.…”

“…Many meningococcal isolates have frame-shift mutations in aniA (29) and cannot grow anaerobically using nitrite as the electron acceptor. Even in meningococcal isolates that retain intact aniA/norB, these alleles appear to be less efficient in supporting anaerobic growth (28).…”

“…Thus, the denitrification pathway plays a crucial role in gonococcal biology, and gonococcal isolates universally have highly functional AniA and NorB proteins. In contrast, meningococci less commonly experience an anaerobic or oxygen-limited environment at the nasopharynx, and a functional denitrification pathway is not essential for meningococcal survival (28,29). Many meningococcal isolates have various mutations in aniA or completely lack the aniA gene (27)(28)(29), which seemingly points to a selection against expression of a functional AniA in meningococci.…”

Anaerobic Metabolism Occurs in the Substratum of Gonococcal Biofilms and May Be Sustained in Part by Nitric Oxide

“…It has been demonstrated that Neisseria meningitidis can respire anaerobically (16,(55)(56)(57). However, AniA is functional in only some strains of N. meningitidis, and it is not required for pathogenesis (63). If an aniA::kan insertion mutant can anaerobically respire through the NorB-mediated reduction of NO, this may also help to explain why biofilm formation is more severely attenuated in the norB::kan mutant (22).…”