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J Bacteriol 2011 Jun;193(11):2804-13

The Moraxella catarrhalis nitric oxide reductase is essential for nitric oxide detoxification.

Wang W, Kinkel T, Martens-Habbena W, Stahl DA, Fang FC, Hansen EJ


Moraxella catarrhalis is a gram-negative obligate aerobe that is an important cause of human respiratory tract infections. The M. catarrhalis genome encodes a predicted truncated denitrification pathway that reduces nitrate to nitrous oxide. We have previously shown that expression of both the M. catarrhalis aniA (encoding a nitrite reductase) and norB (encoding a putative nitric oxide reductase) genes is repressed by the transcriptional regulator NsrR under aerobic conditions, and M. catarrhalis O35E nsrR mutants are unable to grow in the presence of low concentrations of nitrite (Wang, et al., J. Bacteriol. 190:7762-7772, 2008). In this study, we constructed a M. catarrhalis norB mutant and showed that planktonic growth of this mutant is inhibited by low levels of nitrite, whether or not an nsrR mutation is present. To determine the importance of NorB in this truncated denitrification pathway, we analyzed the metabolism of nitrogen oxides by norB, aniA norB, and nsrR norB mutants. We found that norB mutants are unable to reduce nitric oxide and produce little or no nitrous oxide from nitrite. Furthermore, nitric oxide produced from nitrite by the AniA protein is bactericidal for a Moraxella catarrhalis O35E norB mutant but not for O35E wild-type bacteria under aerobic growth conditions in vitro, suggesting that nitric oxide catabolism in M. catarrhalis is accomplished primarily by the norB gene product. Measurement of bacterial protein S-nitrosylation directly implicates nitrosative stress resulting from AniA-dependent nitric oxide formation as a cause of growth inhibition of norB and nsrR mutants by nitrite.

Category: Journal Article
PubMed ID: #21441505 DOI: 10.1128/JB.00139-11
Includes FDA Authors from Scientific Area(s): Biologics
Entry Created: 2011-10-03 Entry Last Modified: 2012-08-29